Ask the Doctor
Gary WilfretHappiness Farms is pleased to have Dr. Gary Wilfret answer your questions on Caladiums.

Dr. Wilfret is regarded by many as one of the world’s leading authorities on Caladiums. He is the recipient of the Florida State Horticultural Society’s coveted Gold Medal Award, and a five time winner of the Society’s Silver Medal Award.
During his thirty year career as a Professor at the University of Florida, Dr. Wilfret developed nine Caladium cultivars now in commerce, including Florida Cardinal, Florida Sunrise, Florida Roselight, Florida Elise, Florida Fantasy, Florida Sweetheart, Florida Calypso, Florida Red Ruffles, and Florida Irish Lace. He also has the honor of having been inducted into the International Gladiolus Hall of Fame.

Dr. Wilfret has authored over 400 articles that have appeared in both national and international publications, and he is a frequent speaker to garden clubs, university classes, and national and international horticultural societies.

Have a question about Caladiums? Click Each week, Doctor Wilfret will select a few of the most interesting questions received, and answer them here in this column. Unfortunately, not all questions can be answered, but Dr. Wilfret will try his best to answer as many as possible. Please, do not phone in your questions. Only questions sent via email will be forwarded to Dr. Wilfret.






Question: In one of the answers in FAQ, you stated that the ammonical form of nitrogen in mature imight not be good for caladiums because of possible diseases. does that also apply to that form of nitrogen in a balanced packaged fertilizer?
Answer: The ideal ratio of nitrate nitrogen to ammoniac nitrogen would be 60:40. This is because Fusarium, a major fungus disease of caladiums, thrives on lower pH and the more ammoniac nitrogen you have, the lower the ph when it dissolves into the substrate. Chemical companies use this form of nitrogen because it is cheaper. Organic forms of nitrogen are also not the best as they break down to ammoniac nitrogen and then lower pH. Add a little lime to the soil not only to raise the pH but to give the roots a source of calcium. Calcium deficiency results in brown blotches in the leaves and eventually large holes in the leaves. Thanks for asking……….. Doc Question: I just observed caladiums that a client has planted: grass green/white variegated medium foliage (don't know the variety, but looks like they need shade) in the full sun. Could they be just reacting to their harsh full sun exposure if symptoms are elongated holes in the leaves that look like a caterpillar might have been eating them? It is only on the leaves at full exposure, underneath leaves look fine. Is that too much sun, too little water, both or other? It looks to me like digging and relocating them is the logical solution but is there by chance in your opinion any temporary potential benefit in trimming off the damaged surface leaves and then spraying the currently shaded leaves with an anti-expirant (basically a wax and distilled water mixture)? The client wants to avoid digging up the extensive bed and needs an aesthetic quick fix for a month or so. Any suggestions? Susan Atlanta, GA
Answer: The large holes in the leaves (probably Candidum or White Christmas) are probably a combination of too much sun, especially for Candidum, and a Calcium deficiency. I would cut off the affected leaves and then try to sprinkle a little gypsum or hydrated lime around the base of the plants and then water it in thoroughly. I would then try to keep the foliage moist with a daily sprinkle. Symptoms of calcium deficiency in caladiums start as tan interveinal blotches than turn a darker brown after 7-10 days. Then, the brown areas dry up and the center of the dark area disintegrates, leaving a large hole that looks like an insect ate it. Try this and see what happens…………Good luck, Doc

Question: I am going to dig out my old flower beds and replace them with new soil before I plant my jumbo red caladiums. What would be the ideal soil to use?
Answer: Caladiums are not too specific about the soil type that they will grow in, as we plant them in a high organic muck soil in the fields when they are being propagated. Some people use straight peat moss when they grow them in pots. What you need is a high organic soil that has both good moisture holding capacity as well as good drainage. For the garden, I would use about 50% peat, 30% composted bark or vermiculite, and about 20% sand. Try to adjust the pH to 5.5 to 6.0.

Question: What caladium cultivars will do well in a sunny location?
Answer: This is a frequently asked question, as not everyone has big oak trees in their yards to shade the caladium leaves. Fortunately, there are several cultivars that do well in full sun, providing the plants get good moisture. Some of the fancy-leaved selections that do well are: Aaron (white); Carolyn Whorton (pink with red veins); Florida Elise (pink); Florida Sweetheart (rose & my favorite); and Red Flash (red). The lance types that are okay in the sun are: Miss Muffet (chartreuse with red spots); Gingerland (white with red spots); and Red Frill (red). Good luck in creating a rainbow of colors with these cultivars.

Question: Please advise when to fertilize my caladiums and what I should use.
Answer: Caladiums should be fertilized every 5 to 6 weeks with a balanced fertilizer, such as a 6-6-6 or an 8-8-8 fertilizer. Try to use one that is not too high in Ammoniacal Nitrogen or sludge, as this encourages Fusarium rot in the tubers. Use about one pound per 100 square feet of bed at these intervals. Regular feeding is generally necessary, since we water caladiums a lot to keep them turgid and happy.

Question: I have planted some caladium bulbs but I don’t know which side of the bulb is up. Does it make any difference? Can you help me out?
Answer: The knobby side of the caladium tuber with the numerous visible eyes is the top. The bottom of the tuber is generally smooth and devoid of eyes that become the leaves. Planting them upside down will delay emergence of the leaves but will not hurt the plants. Try to look closely at the tubers next year before you plant.

Question: I live in South Carolina and have an area under a scrub oak. It forms a triangle with 3 pine trees. I want to cut the pines but my husband will not cut anything! Grass will not grow here because of the shade. I want a showy bank of white caladiums. What do you suggest? My family is coming in July and I want the yard beautiful. Can you help?
Answer: Your choice of tall white caladiums would be Candidum and White Christmas, with Aaron being slightly shorter. Intermediate in height would be Candidum Jr. with the lance leaf White Wing being the shortest. I would use Candidum Jr. as the color is very white, the plants do not get too tall, and the color does not “pink” in the shade. I agree with your husband! Save the trees to give all of us mammals some oxygen to breathe!

Question: Can I grow caladiums indoors in the winter for a bit of color?
Answer: Caladiums do well when grown in containers indoors, especially if you can give them some supplementary light and keep them warm (above 70°F). Since many of the Fancy-leaved cultivars get very tall and stretch under reduced light, I would suggest that you try some of the lance-leaved types, such as Red Frill, Lance Whorton, or Jackie Suthers. These produce a large number of leaves and are short.

Question: I live in Tennessee and if I plant my caladiums after the weather turns warm, by the time they get full and beautiful, the early frost kills them. I dug all of them early and brought them into the house (What a job with all these pots!). Will they grow indoors? Any suggestions for next year?
Answer: I empathize with you and your cold weather. That is why I live in Florida! I would suggest that you start the caladiums in 6 inch pots next year about 3 weeks before you are ready to set them in your outdoor beds. They do not take up much space if you stack them in a pyramid and cover them with a blanket to keep them warm. Then, when you start to see the leaf sheathes just protruding from the soil surface, spread them out until you plant them outdoors. This will give you another month to enjoy these beautiful plants.

Question: Rabbits seem to prefer the chartreuse-green varieties of caladiums in my garden (and coleus too!). The only way that I can grow this color is in hanging baskets that are attached to my barn wall? Have you ever heard of this?
Answer: I have not had this experience with rabbits in Florida, and our alligators are not vegetarians. I would assume that the rabbits are after leaves that have a lot of chlorophyll in them. Other people that have grown caladiums have said that the deer prefer one color over another in their garden, so I guess they are finding something tasty in them. The oxalic acid crystals in caladium leaves would probably irritate the throats of the animals. I am afraid that you will just have to keep these cultivars up out of reach of the pesky rabbits.

Question: I live in Houston and have a 3X20 foot bed in the front of my house that faces north. The area is partially shaded with a huge ash tree, so the bed gets some sun. I was told that Carolyn Whorton will do well in the sun. Is this true? How many tubers do I need for this area, what size tubers do I use, and what spacing?
Answer: Carolyn Whorton does very well in a sunny or partially sunny location, as well as other cultivars such as Florida Elise, Florida Sweetheart, and Fire Chief. I always try to use jumbo tubers in the landscape, as they produce large showy leaves and have a lot of leaves. I would space them on about 10 inch centers to give the maximum effect. Since Carolyn Whorton has large rose/pink blotches with deep red veins, you might want to accent the bed with a solid red, such as Florida Cardinal. It should be very pretty within 7-8 weeks of planting.

Question: I live in Texas. When should the caladiums in my garden start to grow?
Answer: If you are in southern Texas, they should start to show leaves about the middle of April, providing you do not have a late cold spell. People in northern Texas will have to wait until May to see these beautiful leaves. Be patient and they will display their beauty soon.

Question: My caladiums are beautiful in my garden but something is eating the leaves right down to the stalk. We do have deer in the area but you said they probably wouldn’t graze on caladiums. What could be eating them?
Answer: My first two choices would be either grasshoppers (large lubbers) or some type of worm, such as an armyworm. Generally, grasshoppers eat only parts of the leaves, leaving large holes readily apparent as you view them. They tend to be visible in the early morning or in the late evening when the leaves are damp and luscious. If you see grasshoppers, a few good whacks with a flyswatter or trapping them between two boards is very effective. I have found them to be great bass bait and have done very well in the local ponds catching fish. If you don’t see grasshoppers, the next choice would be armyworms. Look on the underside of the young leaves to see any larvae that might be crawling around. Also, check the soil at the base of the leaves to see if any worms are curled up in the upper surface of the soil. They love to hide there during the day and forage at night. If you want to try a preventative spray purchase some form of Baccillus thuriengensis, a bacteria that disrupts the intestines of the young larvae, causing them to die. It only is effective on young larvae and does little for large worms. Your other choice is to pick them off the plant and squash them. Not a pleasant task, but effective. Let us know what you find.

Question: How do caladiums reproduce? Do they divide like lilies or daffodills?
Answer: I am in the process of writing a series on how to breed caladiums that you will find on our web page during the next few months. Keep looking and get a step by step cookbook. But, a simple answer to your question is that caladiums reproduce both sexually from seed and asexually from pieces (chips) of the tuber, much like that of a potato. To get seed, you have to manually pollinate the flowers to form a fruit and ultimately harvest the seed. In this manner, you get new combinations of leaf colors, patterns, and shapes. By cutting up the tubers in pieces, with each piece having an "eye", you get plants that are identical to the parent. If you really want to be fancy, you could propagate them through tissue culture to theoretically produce thousands of identical clones within a very short time. One has to be careful of the latter method, as the plants in tissue culture can mutate and produce abnormal plantlets. Hope this gives you a quick answer. Look for the upcoming series on breeding of caladiums.

Question: My caladiums are really growing fast, and I am afraid that they will run out of fertilizer. What do I use and how much?
Answer: In general, caladiums are not "heavy feeders" and require only a moderate amount of fertilizer. Your soil type and temperature will also affect the amount of fertilizer you need. Plants grown in sandy soils and with higher temperatures will require more fertilizer than those grown in organic soils and at cooler temperatures. As a general rule of thumb, use between 1 and 1.5 pounds of a 8-8-8 or 10-10-10 fertilizer per 100 square feet of planted area. You could apply this amount every 5 to 6 weeks. If you live in a hot rainy location with sandy soils, you will need to increase the frequency. If you like to use a liquid feed program, use a 500 ppm Nitrogen solution of a 20-20-20 about every 2 weeks. In Florida if we get 1.5 inches of rain on our sandy soils, all the Nitrogen and Potassium will be gone so we need to apply more fertilizer. In organic soils, it doesn't leach out as badly. Remember that use of too much fertilizer is not good for the environment. It is always better to use less fertilizer and make more applications.

Question: I love the caladiums that you send but do I have to dig them up in the fall and store them during winter in a warm place?
Answer: Since caladiums are tropical plants with a center of origin in Brazil, they do poorly when temperatures get below 60°F. This seems to be a popular question. People want to plant them like hosta or daylilies and leave them in the ground, sometimes covered with heavy mulch. The best way to answer this question for your growing area is to ask yourself if the soil temperature 3 to 4 inches deep is below 60°F during the winter in your garden. If the answer is "yes", then you need to dig the tubers and store them where they will stay at least 70°F. Be sure to let them dry before you place them in a paper bag for the winter. If you have access to a fungicide, dipping the tubers after digging in a fungicide solution will help to keep them healthy for the next year. It takes a little work to save the tubers, but you will get the satisfaction of seeing those colorful leaves next spring. If you live in Orlando, FL or south, leave them in the ground. Otherwise, dig the tubers when the leaves desiccate after the first frost.

Question: I know that caladiums do well in shaded locations in the garden but are there any cultivars that can be grown in the full sun and not burn?
Answer: A simple answer is “yes”. One of the objectives of my breeding program was to develop caladiums that can be grown in sunny locations without fading or developing burned leaves. But, the most critical aspect of growing caladiums in sunny areas is to keep them wet. Never let the plants wilt due to lack of water, as they will not recover to their previous vigor and beauty. Listed below are some cultivars that you should try:
White……....Aaron
Pink/Rose….. Carolyn Whorton, Florida Elise, and Florida Sweetheart
Red…...... Red Flash
Novelty….. Miss Muffet, and Gingerland
Lance….... Red Frill (Red)

Question: I have a lot of Black Walnut trees around the house and plants have a difficult time growing under them. Will caladiums be a possible choice of plants?
Answer: As you are probably aware, black walnut trees exude a toxin that tends to inhibit the growth of most plants in their proximity. I would guess that caladiums would not do well if the tubers are planted in the ground close to the tree roots. But, there is a solution to that: just plant the tubers in containers that contain a potting mix that you can buy from your local garden supply store. Make sure the soil has a high organic (peat moss) content that will hold moisture and has a pH of 5.0-6.5. You can mix a slow release fertilizer in the soil before you plant. I would use three #1 or one jumbo tuber per six inch pot. Cover the tubers with at least three inches of soil. Bury the pots around the tree up to the lip of the pot and then cover the area with some type of organic mulch about two inches deep. Water the plants regularly, stand back and watch them grow!

Question: Do deer eat caladiums and are they poisonous to my pets?
Answer: I have not heard of deer eating caladiums, but we do not have many episodes of deer getting into flower beds in Florida. Our deer population is so small that the probability of a deer eating our caladiums is pretty unlikely. I am sure areas of the United States that have a large population of deer might have a problem, but I haven’t heard of such a situation. Caladiums, especially the tubers, contain crystals of oxalic acid, which would cause a nasty taste in an animal’s mouth, similar to that found in many aroids. I know of cattle that have eaten some leaves, but they soon find tastier leaves. Wild and domestic pigs will uproot the tubers, but they also leave them alone after a few nibbles. We have ten (10) domestic cats in our house and have not seen any evidence of grazing on the caladiums on the patio. They seem to prefer plants with elongated leaves, such as the Dracaena and Palms, they shred these. Maybe they are cleaning their teeth, like flossing! I would like to know if people have a problem with deer eating their caladiums. Some people can get a mild rash from the juicy latex found in the caladium tuber, so it is always a good idea to wear garden gloves if you cut the caladium tubers into smaller pieces. This rash will go away in a few minutes, but it can be itchy.

Question: I recently bought some caladium tubers and I don’t know which is the top and which is the bottom. One side has bumpy knobs with some fuzzy roots and the other side is smooth. Help please……
Answer: It can be confusing to gardeners who buy caladium tubers for the first time and can’t determine up from down. Generally people receive the tubers prior to the development of leaves or even before the tubers begin to spike. All they see is a dried brown mass with some squiggly dried brown roots left over from the previous season. The top of the tuber has the dormant eyes, which will develop into the beautiful leaves, and the bottom has a smooth sterile surface. What is confusing is that the new roots develop around the eyes on the top of the tuber and not on the bottom as with other bulbous crops such as lilies, gladiolus, etc. This is why it is so important to cover the tubers with at least 2 to 3 inches of soil when they are planted so that the young roots do not get too hot or are allowed to dry out. Once caladiums wilt and the roots wither, the plants will never regain their expected vigor. Remember to always keep caladiums warm and wet, and they will reward you with a magnificent display of color in your garden.

Question: Would it be okay to use Bulb Booster in the planting hole when planting caladiums? Also, would soaking the tubers in a liquid kelp solution prior to planting help the plants grow?
Answer: The major ingredients in any type of preplanting fertilizer or growth enhancer are generally potassium, phosphorus, and some hormones that promote root growth. Any help that you can give to the plants to get them started will be beneficial; just don’t overdo the amount that you put in the hole. Remember that roots of caladiums develop on the top of the tubers, so don’t cover the tubers with anything but good soil that has low soluble salts. Also, never fertilize caladiums, either in the planting hole or in the beds with manure. The ammoniacal form of nitrogen that results from the degradation of manure can increase the sensitivity of the plants to certain soil diseases, such as Fusarium. Kelp solutions have been promoted for years as a growth enhancer, as kelp contains most of the base elements needed for plant growth, many vitamins (most of which are better for people than plants), and some growth regulators that enhance rooting and the uptake of nutrients. You certainly will not harm the plants and the added nutrients could increase plant growth. Just use a low concentration so as to not damage the developing leaves and roots.

Question: What do you consider the best pink caladium cultivars to grow in the garden?
Answer: My choice of pink cultivars depends upon where the plants are to be grown, such as in partial shade or full sun. Yes, caladiums can be grown in full sun as long as you grow the right cultivars and keep the plants well watered. In shady locations, Kathleen is a beautiful full pink with a medium green margin. But, it fades to a brownish pink in high light conditions. Pink Beauty has many pink blotches with green veins and the blotches coalescing into almost translucent areas. Fannie Munson is also a favorite, but it is a rosey pink overlaying a venation pattern similar to the popular Candidum cultivar. Of course, I am biased, but the most beautiful pink/rose is Florida Sweetheart, developed by yours truly. This is intermediate to a fancy and a lance leaf and is great for the garden or pots. It will not over-winter, as the tubers are very sensitive to cold temperatures. Just enjoy it this year and buy new tubers next year! In full sun, Pink Beauty is good but Florida Elise doesn’t burn and maintains its medium pink color. If you are looking for a multicolored plant, Carolyn Whorton has large pink blotches with dark red main veins and is a strong plant in the sun. Florida Sweetheart also does well in the full sun as long as it gets plenty of water. Try some of these and let us know how they do in your garden.

Question: Since I live in Minnesota, how can I get caladiums to start growing earlier so that I can enjoy them longer during the season? If I wait until it warms above 55°F, I don’t have plants until July.
Answer: Realistically, the only way to get your plants to grow sooner in the year is to start them indoors where temperatures are above 65°-70°F. You could start them in pots where it is warm and transplant them in bulk when outside temperatures are better for these tropical plants. Remember to water them in the pots with “warm” water, not from the typical faucet water of Minnesota. I tried to brush my teeth with your tap water one year and felt like I was being tortured. We start digging caladiums in Florida in November and then the tubers are dormant for 8-10 weeks before they will start to grow. Theoretically, you could order the tubers for delivery in February or March and get the plants started very early. The major problem with this is that the tubers could be damaged during shipment, where temperatures can get below the optimum of 55 F. You would have to assume this risk. Talk to the sales department about your options.

Question: R.J. of LaPaz, Mexico planted caladiums in containers last fall and now the leaves have died with just the tubers left in the soil He writes to ask what he should he do with these plants now?
Answer: Caladiums are tropical plants, generally from the Amazon basin of Brazil, where the seasons alternate from wet to dry conditions. During the wet warm times of the year, caladiums continually produce new leaves and make a beautiful, colorful display on the forest floor. During the dry season, the roots wither, interrupting the uptake of water to the leaves and these leaves dry up. A tuber, similar to that produced by a potato, forms at the base of the leaves and goes dormant. In nature, the tuber remains dormant for at least eight weeks or until the rains begin. Cold weather, with temperatures below 55°F, can also trigger the decline of the plant and induce dormancy. The latter condition is the cause of the decline of caladium plants when they are grown in containers or in the gardens of temperate climatic zones of the world. It is Mother Nature’s way of preserving the species so that it can grow the next year. Your plants grew as they were programmed and now they are dormant. The best way to assure beautiful plants next year is to purchase new tubers. If you are adventurous, you could dig the old tubers, wash off the soil, dry the tubers for three to four days at 80°F, place them in a paper bag, and store them at 70°F and 60% relative humidity for at least eight weeks or until night temperatures are above 55°F. Then plant the tubers upright, with at least two inches of soil over the top. Generally, the harvested tubers are very small and do not produce the large showy leaves that develop from the new tubers of commercial growers.

Question: Greg wants to grow caladiums for use as cut foliage and wants to know how many leaves to expect in a year, if some varieties do better than others, and can they be refrigerated?
Answer: The number of leaves produced by caladiums depends on multiple factors: 1) Size of the tuber planted. Jumbo and mammoth tubers will yield the greatest number of leaves.
2) Leaf type. The lance leaved cultivars generally have more leaves and last longer when cut than the fancy leaf types.
3) Cultivar. Generally the cultivars that have thicker leaves, such as Carolyn Whorton, do better cut than those with thin leaves.
4) Growing duration. How long will you be able to grow the plants before night temperatures are below 55°F, which induces dormancy in the plants? On average, you should expect 40 to 50 leaves per year from lance cultivars and 20 to 35 leaves from the fancy leaf types. But remember, caladiums are tropical plants and cannot be refrigerated for storage. Contact Happiness Farms to get a selection of the best cultivars to grow.

Question: John, a grower at a greenhouse in Michigan, would like to know if any growth regulator is effective on caladiums.
Answer: I have tried many growth regulators on caladiums in an attempt to produce shorter plants, to induce more leaves to develop, or to break the natural dormancy of the tubers. To date I have found no chemicals, including Florel or Ethylene Chlorohydrin that are effective in breaking dormancy or cause more leaves to develop from the tubers. The most effective growth regulator to retard plant height has been Bonzi, used as a 30 minute soak of the tubers prior to planting. In Florida, the optimum concentration of Bonzi was 20 to 30 ppm for 30 minutes. The tubers were then air-dried for 24 hours at 75°F and planted in containers. You need to evaluate concentrations that would be suitable for your area, probably in the 10 to 30 ppm range as a guideline. A soil drench of Bonzi, applied at the “spiking” stage has shown some effect, but a tuber soak would appear to be more efficient. Let us know if this works for you.

Question: I have a beautiful "mystery" plant that a friend gave me, but I'm not sure how to take care of it. I think it's a caladium, but I'm not sure. I am attaching some pictures, is this really a caladium?? I have it in partial sun, water it once a week, it was going great guns for a while but now its growth has slowed almost to nil and it's getting some rust colored dime sized spots on the edges of its leaves. I have attached some photos....Any advice would be appreciated! L.M.
Answer: The plant in the pictures is not a caladium but is in the same aroid family, which includes the elephant ear group of plants. These plants are difficult to identify in a picture, but this is either in the genus Colocasia or Xanthosoma. They make beautiful specimen plants and will grow a long time if they are kept warm, well watered, and fed about once a month with a liquid fertilizer. The yellow spots on the margins could be a reaction to cold weather (Is that snow I see outside the window?), a deficiency of potassium (Time to give the plant some food!), or a bacterial infection (We won't even give this a second thought!). My suggestion would be to cut off the leaves that display the yellow spots, feed the plant with a good liquid fertilizer and put it in a warm area of the house. If the plant gets too cold or dries out, it will go dormant and form a tuber. You could then dig the tuber, wash off the old soil, dry the tuber , place it in a paper bag and store it for six to eight weeks at 70°-75°F. Plant the tuber in a new pot with fresh soil when it warms up this spring. Good Luck.

Question: How do I get my caladiums to produce more leaves? I've heard that planting them upside down will cause more leaves to develop.
Answer: Planting caladium tubers upside down only delays leaf emergence. It does not cause more leaves to form. The best way to get more leaves is to "de-eye" the tubers before planting. Using a thin sharp knife, remove the center one-eighth inch of each large dominant eye (bud), or use a large nail to punch the center of each main eye about one-quarter inch deep. This kills the main bud and forces the lateral buds to grow and form more, but smaller leaves.


Question: Can I leave my caladium tubers in the ground over winter and will they grow next year?
Answer: Caladiums are tropical plants from South America and do not tolerate soil temperatures below 55°F. If your soil is below this temperature during winter, you must dig the tubers when all the leaves begin to wilt or just after the first frost. Store dried tubers in a warm room, preferably above 65°F and replant them in the spring when night temperatures are above 55°F. Better yet, discard the old tubers and buy new ones in the spring.

Question: How do you breed caladiums?
Answer: (First of a series: Introduction) This cannot be answered without a lot of explanation and dialogue. Since I have had many requests for this information, I am going to do a series of articles giving you the basics of caladium breeding, my objectives, and successes. Introduction: Caladiums are tropical plants, with a center of origin in South America, specifically Brazil. They are members of the aroid family, related to the green elephant ear, taro, and tapioca plants. They form tubers, similar to a potato, with numerous eyes that develop into leaves. The plants are very cold sensitive and prefer temperatures above 65°F and lots of moisture. If the plants get cold, the leaves will wilt and the tubers will go into a resting stage for eight to ten weeks. Dry weather will also cause dormancy, as the roots will dry up and the plant goes to sleep. This is a natural occurrence in the tropics where the seasons are more noticeable between wet/dry than cold/warm. The flower of a caladium consists of a spathe (the fleshy outer covering) and a spadix (the conical inner stalk that contains the male and female flowers). The male flowers are at the tip of the spadix, a sterile area of tissue is in the middle, and the female flowers are at the base. Caladiums are “protogynous”, which means that the female flowers are receptive before the male flowers shed their pollen. This is why you rarely observe seed on your caladium flowers. The female flowers have to be pollinated from the pollen of another flower on the plant or another plant. Most people cut off the flowers, as these structures can use some of the nutrients that could be going to the leaves, which are why we grow caladiums in the first place. A good reference on hybridization of caladiums is: Hartman, R.D., F.W.Zettler, J.F.Knauss, and E.M.Hawkins. 1972. Seed propagation of caladium and dieffenbachia. Proceedings Florida State Horticultural Society, pages 404-409. Following articles will provide you with this methodology…. keep looking at our web page for the latest installment.

Question: How do you breed caladiums? (second in a series: Breeding Objectives)
Answer: Although people in Europe, South America and the United States have been hybridizing caladiums for the past 150 years, nobody has produced that perfect caladium that meets all the criteria of perfection. The perfect caladium cultivar should have brightly colored leaves, be unique in its color pattern, have strong upright leaves, produce many leaves, be tolerant of the major diseases, such as Fusarium and Erwinia, be resistant to nematodes, and produce large multi-segmented tubers. The plants should grow early in the spring and have some cold tolerance so that they can be grown in regions of the country that have cool nights, even in the summertime. That is a lot to ask of one plant, but all breeders have to set the ultimate goals in their hybridization. Some helpful hints to start you in breeding are: 1) If you cross a solid red fancy leaf (Florida Cardinal) with a netted venation fancy leaf (Candidum), all of the progeny will have some degree of netted venation with a prominent red main vein; 2) If you cross any of these progeny back to a netted type, half of the seedlings will be netted and half will be netted with a red main vein (White Queen); 3) If you cross a netted type with a cultivar that has large blotches (White Christmas), half of the seedlings will be netted and half will have large blotches; 4) If you self pollinate a netted type that has a red main vein, one quarter of the progeny will be netted with a green main vein, one half will be netted with a red main vein, and one quarter will have a solid red center; and 5) If you cross a plant that has both pink and white spots with a plant that has no spots, one half of the seedlings will have pink spots and one half will have white spots. There are also modifying genes that cause the intensity of the pink to vary from a light pink to a dark rose. Red spots are also inherited in the same manner. This gives you some idea of the complexity of caladiums and how one can spend 30+ years trying to find the “right” plant, as I have done. If anyone cares to know more of the inheritance of other characteristics, drop a note to our web page. A good reference to start your reading on caladium genetics is: Zettler, F.W., and M.M. Abo El-Nil. 1979. The Journal of Heredity 70:433-435.

Question: How do you breed caladiums (Third in a series: Gibberellic Acid Soak)
Answer: Not all caladium cultivars readily make flowers when they are planted in containers or in the landscape, nor do they flower at the same time. Sometimes they flower when one least expects it, such as after just a few leaves have unfurled. People often ask what they are and if they should cut them off. Since they add very little decorative value to the plants, the flowers should be cut off just above where they emerge from the leaves, unless of course you want to hybridize. Back in 1979, we learned how to fool Mother Nature into getting the caladiums to flower consistently and fairly uniformly. Tuber size has a big influence on flowering, as the larger tubers (Jumbo and Mammoth) produce more flowers than the smaller tubers. We found that soaking the tubers for eight (8) hours in a 250-500 ppm solution of Gibberellic Acid prior to planting, enhanced flowering over those tubers soaked in water, with plants flowering about 60 days later. Each tuber treated with Gibberellic Acid yielded about three (3) flowers. The 10 inch pots should be planted with 4 to 5 jumbo or 3 mammoth tubers, with about 3 to 4 inches of soil over the top of the tubers. Leaves should begin to unfurl within 2 to 3 weeks and the flowers should be mature in about 60 days. If your plants are already growing and you want to get them to flower, spray the base of the plants to a heavy runoff (sprenching) with a 500 ppm solution of Gibberellic Acid. I found that cutting off all the leaves about 2 inches above the pot prior to applying the Gibberellic Acid allowed the spray to get to the base of the leaves easier. Some cultivars will produce numerous flowers while others produce few. Try to get as many pots as you can started in the early spring in order to get a second flush of flowers in August to double your chances of getting the crosses that you want. I would suggest that you initially cross some of the solid red fancy leaf types (such as Florida Cardinal, Poecile Anglais, Postman Joyner, and Buck) and some of the red lance leaf types (Florida Ruffles and Red Frills) among themselves. When you get more ambitious, you can incorporate plants with netted venation, spots, and blotches. A good reference to this method is: Harbaugh, B.K. and G.J. Wilfret. 1979. Gibberellic Acid (GA3) stimulates flowering in Caladium hortulanum Birdsey. HortScience 14(1): 72-73.

Question: How do you breed caladiums? (Fourth in a series: Pollination)
Answer: Once you see the flowers begin to develop and elongate, your adrenalin should start to flow and the excitement begins in anticipation of actually hybridizing plants. Remember that caladiums are protogynous, meaning that the female flowers are receptive before the male flowers shed their pollen. Actually, the female flowers on the caladium inflorescence (the spadix) are receptive about three (3) days before anthesis (pollen visible). The spadix is covered by a green leafy structure called a spathe, which turns a creamy white color when it unfurls. Unfortunately, when the spathe unfurls to reveal the spadix, the female flowers are no longer receptive and are covered with a gelatinous mass that inhibits pollen tube development. To understand the pollination of caladiums in nature, one has to assume that some insect (probably a beetle) bores a hole in the spathe in search of the nectary to get a sweet drink. He probably has visited other mature caladium flowers in close proximity and some of the pollen from these flowers has attached to his legs and body. As he roams around inside the unfurled spathe, he walks over the female flowers and pollinates them with the attached pollen. If you exam the spadix, the female flowers are at its base, closest to the nectary, and the male flowers are at the uppermost tip. So, how do you know when the female flowers are receptive? As the spathe develops, it is medium to light green in color, depending upon the cultivar. Sometimes, it even has white blotches on it. One has to observe the developing spathe carefully, waiting for a change in color along the margins where they overlap. When the margins of the spathe just start to turn creamy white, the female flowers are receptive. At this point, one takes a sharp scalpel or knife and carefully circumcises the spathe about one quarter inch above its base. Do not cut too deep or you will damage the female flowers. If you have done this correctly, the spathe will slip off the spadix, revealing the inflorescence. Now, collect pollen from another flower that has matured and brush the pollen all around and over the female flowers. The pollen will survive for 2 to 3 days on the female flowers if you have started too early. Remember, if the female flowers are covered with a sticky substance, you waited too long to pollinate. Repeat these steps for as many flowers as develop. You can try to store pollen in plastic containers (I use 35 mm film canisters) in the refrigerator for a few days or you can put the canisters in the freezer for a few months. I have had limited success with pollen frozen longer than 4 months. Maybe the tropical nature of the plant prevents freezing of the pollen. Would be a good research project for a science student. Good luck with your pollinations and continuing reading our web page for more in this series, such as what to do next!

Question: John, a grower at a greenhouse in Michigan, would like to know if any growth regulator is effective on caladium.
Answer: I have tried many growth regulators on caladiums in an attempt to produce shorter plants, to induce more leaves to develop, or to break the natural dormancy of the tubers. To date I have found no chemicals, including Florel or ethylene chlorohydrin that are effective in breaking dormancy or cause more leaves to develop from the tubers. The most effective growth regulator to retard plant height has been Bonzi, used as a 30 minute soak of the tubers prior to planting. In Florida the optimum concentration of Bonzi was 20 to 30 ppm for 30 minutes. The tubers were then air-dried for 24 hours at 75 F and planted in containers. You need to evaluate concentrations that would be suitable for your area, probably in the 10 to 30 ppm range as a guideline. A soil drench of Bonzi, applied at the “spiking” stage has shown some effect but a tuber soak would appear to be more efficient. Let us know if this works for you.

Question: Bernie Bowden asks “I have caladiums plants appearing in my garden and the only reason that I can put on it is they are self propagating and if you cut the spadex off and put it in the garden it will disperse seeds if it self pollinating is this correct?”
Answer: Generally caladiums are not self-pollinating, as the female flowers at the base of the spadix are receptive a few days before the pollen is formed on the male flowers at the top of the spadix. So, if you find fruit developing on the spadix, the pollen came from another caladium flower. When the fruit do develop and mature, you can remove the seed from the berries and plant them in a pot. Disperse the seed on top of the soil and do not cover them with other soil, as they require light to germinate. When the seedlings grow, transplant them to larger pots or into your garden. Sounds like fun to me.

Question: Don Gillette was told to add peat humus to his soil, and wants to know if it is the same as peat moss???
Answer: Humus is any composted material, such as garden waste that you would use in a compost pile in your home garden. Peat is actually a form of humus from partially decomposed plant materials. Thus peat moss is a form of humus. I have seen bags of compost that say they contain peat moss and composted organic matter. These could be used as supplements in growing caladiums but make sure the mix is not “hot” with high levels of ammonium nitrogen. High ammonium levels could burn the roots as well as encourage the development of fungal caused diseases. I prefer adding peat moss to the potting medium at 40 to 50%. Be sure to supply calcium to the mix so you get healthy plants. Good luck.

Question: Gustavo Girardelli of Sao Paulo, Brazil sent in the following questions regarding the culture of his caladiums. 1. Which the substratum I must use for the plantation of tubercles? 2. Which the seasonings I must use; as much chemistry as organic? 3. The PH, influence in the culture? 4. How many times I must water mine caladiums? 5. I am cultivating mine caladiums in vases, will be that it has some problem?
Answer: I will try to answer your questions on the culture of caladiums: 1. The best medium for growing caladiums is about 50% organic matter (peat moss or compost) plus sand and material to add porosity to the mix, such as perlite, or even Styrofoam pellets. 2. The ideal fertilizer would be something like a 10-4-10 mixture that was made from about 25% organic matter. You do not want high levels of ammonium nitrate, as this will lower the pH of the soil and also encourage diseases. If in pots, the plants should be fertilized monthly with about a teaspoon of this mixture per 6” pot. 3. The pH of the soil should be from 5-6, but be sure to add calcium to the soil for tuber development and leaf formation. 4. Watering has to be done on a “look-see” basis, meaning when the soil in the bottom of the pot is slightly dry, water the plants. Never let them wilt! 5. Caladiums will grow in many containers; just make sure they have drainage holes in the bottom so the plants are not water-logged. Good luck and let us know how you do with your caladiums.





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