Cultural Pot Production

Pot Production

All caladium varieties may be used for pot production. However, certain varieties are more suited for certain pot sizes than others. The following guidelines will aid the commercial grower in successfully producing highly marketable pot caladiums.

De-eyeing

Various techniques have been used in the past to finish caladiums that have a more compact habit with more leaves. Terminal bud removal or de-eyeing, is the most reliable way. Individual varieties respond differently to this procedure, with some showing no appreciable affect from the procedure. To de-eye, cut out the dominant buds or sprout(s) (eyes) using a small knife. Staying within the diameter of the eye, remove the entire eye by cutting about ¼ ” deep into the bulb (see diagram). Remember, it is critical to stay within the diameter of the eye to eliminate damage to the small eyes that surround the perimeter of the main eye. Experiments using a nail to puncture and destroy the terminal bud have shown good results. Remember in order to be effective, the de-eyeing method must remove or destroy the terminal buds. Please note however while proper de-eyeing increases the uniformity of your crop, increasing the severity of the de-eyeing treatment, by excessive removal of tuber tissue, leads to a less uniform crop. Cluster bulbs with four or five dominant eyes generally do not benefit from de-eying. Contrary to some beliefs, it is not harmful to de-eye white cultivars as long as it is done properly, e.g. stay within the diameter of the eye. The caladium bulb, being a storage organ, is full of carbohydrates. A wet carbohydrate source invites disease problems, so it is best to let a de-eyed bulb dry and heal 10-12 hours before potting. It is helpful to use a fungicide or Talc dust to aid in this process. Good air circulation is very important to this drying (healing) process.

Growth Regulators

Growth regulators such as B-9 and Bonzi have proven to be useful for various growers around the country. Despite this success, we believe the best height control method for the pot plant trade is to use the proper de-eyeing technique, proper spacing, timely removal from bottom heat and selection of the proper bulb size and variety for the finished pots you are trying to create. In most cases, No. 2 bulbs produce smaller leaves and a somewhat shorter plant. Of course too much shade will cause stretching.

The following growth regulators have been tried by various growers and research institutes. Serious caladium growers should conduct similar tests:

  1. Bonzi – Soil Drench. Apply when plants show a few spikes, and are not yet leafed out at the rate of 8 PPM. Remember to wait for the first spikes to show since only a well-developed root structure will take up the Bonzi. The medium needs to be moist, not dry. Pine bark in the mix will reduce the effect of a Bonzi drench and the concentration will need to be increased by about 50%.

  2. Bonzi – Tuber Soak. Soak tubers for 30 minutes after de-eying in a 30 ppm (1oz/gal) Bonzi solution, allow bulbs to dry overnight on the bench and pot them the following day. This will be effective in reducing the height in cultivars like Aaron, Carolyn Whorton and White Christmas and result in an overall more compact plant. We also know of growers that use a 5 ppm bulb soak for 20 minutes then allowing the bulbs to dry overnight before potting. This proves to be as effective as de-eying. As always, when using a drench or a soak, the rate depends entirely on your growing conditions. Growers should experiment to determine the proper rates and exposure for given varieties.

  3. Bonzi – Foliage Spray. Some growers have found a Bonzi Spray at low concentrations (1oz/gallon or 30 ppm) effective in holding plants. Experiments should be considered if using this material in this manner.

  4. B-9 – Foliar Spray. Rate: 1 pound per 40 gallons of water, 2500 PPM as needed; 5-7 days apart, two or three times when leafed out and spaced. B-9 also makes for a very sturdy plant, and increases the shelf life of the finished product.

Pot Size

Pot Size: 4” (10.2 cm) Pot – 1 Bulb No. 2 size or 1 Bulb No. 1 size
6 ½” (16.7 cm) Pot – 6 Bulbs No. 2 size or 3 Bulbs No. 1 size
10” (25.5 cm) Bulb Pan – 8 Bulbs No. 2 size or 4 Bulbs No. 1 size
10” (25.5 cm) Hanging Basket – 6 to 7 Bulbs No. 2 size or 4 Bulbs No. 1 size (use strap leaf cultivars for basket production).
Combination pots and planters – see below

*** Seed stock bulbs (No. 3 size) are recommended for 4 ½” pots and under. Fill the pot 1/3 with soil, add bulbs to cover the surface area of the soil then cover soil.

Combination Pots

Combination pots and planters are becoming very popular and special note should be made of the use of caladiums for this purpose. Caladiums have been identified as the perfect accent plant in combination with bedding plants or in combinations with other caladium varieties. For instance, a bowl with caladium White Christmas in the center and marigolds or wave petunias around the periphery is spectacular. Another dynamite combination is caladium White Christmas in the center with caladium Red Frill around the periphery. Different height effects can be achieved by variety selection, bulb size and whether bulbs are de-eyed.

Potting Depth

Bulbs should be covered with at least 1 to 1 ½ inches of soil. This will ensure adequate soil moisture around roots as they emerge from the top of the bulb. During the initial growing process, caladiums like to be grown moist.

Potting Mixtures

A well-drained potting mixture containing considerable organic matter is suggested. Potting mixtures such as (1) 50% peat moss and 50% shavings, (2) 80% peat moss and 20% pine bark, (3) pure peat moss, (4) organic matter and sandy soil combinations have been used successfully for growing caladiums. A pH-adjusted pre-mix of peat moss, perlite and a wetting agent seems to work best for most caladium growers. It is worth noting that caladiums thrive in the new Pindstrub potting mixes (where available), because of it's water holding capacities.

Planting Time

Though many growers plant earlier, we recommend waiting until after January 15 to plant. A well-cured bulb will out perform a “green” non-cured bulb anytime and will usually finish just as fast as the bulbs planted 2-3 weeks earlier. Certain varieties are slower to emerge than others, so please consult your ABI representative.

Forcing

When caladiums are forced early as a pot plant it is necessary to maintain a higher potting medium temperature for proper sprouting. Sprouting will be sparse when soil temperature is maintained at 60°F (15°C). Sprouting will occur at a soil temperature of 70°F (21°C). However, bulbs sprout best when soil temperature is elevated to 75-78°F (24°C) in the presence of high humidity (85-90% relative humidity). To approximate these conditions heating cables or other means are used to provide bottom heat. The suggested night temperature of the greenhouse for caladiums is 65°F (18°C) or higher. Nighttime temperatures of 60°F (15°C) and below result in injury or reduced plant quality. Early caladium plantings (January to February) require longer forcing periods than later plantings (May). Those forced in January or February generally require eight to ten weeks before plants are sellable, while plantings made in May require about four to six weeks to finish. In order to avoid greening, overheating, stretching, or moisture buildup (which causes bulbs to rot), it is not recommended to cover up newly potted plants with a plastic cover. This will probably do more harm than good. In addition, covering with plastic can cause a buildup of Methane and other toxic gases and stop all growing. If a cover is used, allow for proper ventilation on a regular basis to make sure the potting medium temperature does not exceed 85°F (29°C) or else you will overheat the crop and achieve only erratic growth at best.

Watering

The pots need to be kept moist until the bulbs have sprouted. After they have sprouted, keep the plants uniformly moist until spacing out and the finished size is reached. As plants approach finished size, let the soil dry out slightly (but not to the point of wilting) between watering to harden the plants before shipping. Do not let the plants get too dry, or they will show edge burn and go into early dormancy. Older severely wilted leaves generally will not recover even after watering, and shall be removed.

“Greening” of Caladiums

In most cases, “greening” is a self- inflicted injury that is usually more visible in white cultivars.

  • If newly planted flats are covered with plastic to achieve higher soil temperatures (when bottom heat is not available), do not do this with the white varieties. If flats are stacked, make sure the white varieties and Fannie Munson are always on the top or they will be green. These varieties cannot be placed in the dark.

  • Do not leave caladiums on bottom heat for more than 3-4 weeks; the end result will be a weak, floppy plant.

  • Make sure the de-eyeing incision stays within the diameter of the eye, and will not eliminate the ancillary eyes.

Diseases

The most common diseases are Fusarium and Pythium. The main symptom is root rot. Use fungicides such as Medallion to control Fusarium and Subdue to control Pythium. A fungicide drench should be applied 1-2 weeks after planting to control these fungal pathogens.

Sunburn

White and pink cultivars that have been grown during cloudy, early spring days and are suddenly exposed to high light intensity might show brown blotches on the leaves. Additional shade will stop this problem. Fannie Munson is usually first to burn, so it may be useful as an indicator plant.

Stunted Growth

Make sure that bulbs are not stored at temperatures below 60°F (16°C), or above 90° (32°C). Injury due to temperature exposure manifests itself in stunted (sometimes very slow) erratic growth even though the bulb does not show any injury at all.

Other Foliage Problems

Pink areas in white cultivars like White Christmas usually are a stress related symptom. High temperatures (>100°F) can induce this symptom. As you can cool off your crop this problem should disappear if it has been caused by high temperature.

Leaf Spots

A bacterial leaf spot may occur that is caused by a bacterial pathogen known as Xanthomonas. To prevent damage due to Xanthomonas, be sure plants are well spaced, that there is plenty of air circulation and keep the foliage dry. The bactericide Agrastrep, can be a useful spray material but the cultural controls listed above are best. Nutrient imbalances may cause leaf spots (Ca and K esp.) A pH higher than 7.0 is also known to cause brown spots.

Other Foliage Problems

Pink areas in white cultivars like White Christmas usually are a stress related symptom. High temperatures (>100°F) can induce this symptom. As you can cool off your crop this problem should disappear if it has been caused by high temperature.

Fertilization

Although many growers do not fertilize, we recommend:
50-100 PPM N (constant) of 6-6-6 or 20-20-20 or
300 PPM N (weekly) with fresh water in between

Light Intensity

Caladiums can be forced under a wide range of light intensities. Forty percent to sixty percent shade (achieving light levels of 2500 to 5000 foot candles) seems to be acceptable. In northern areas, it may be possible to produce caladiums under 0-20% shade, since light intensity is not as high as in the south.

Insect Control

Caladiums are rarely affected by insects or related pests. But a good pest-monitoring program together with Orthene is recommended for the control of aphids. A general all-purpose insecticide is usually sufficient.

De-Eyed Versus Non De-Eyed Caladiums

Preparation of Caladium tubers for pot plant forcing. (A) Removal (scooping) of the central or dominant bud(s) will cause the tuber to produce many small shoots and leaves. (B) Planting the entire tuber will produce a plant with a few large leaves.

The Data for preceding Caladium Trials was obtained through research and trials conducted by ABBOTT-IPCO, Inc. in Texas, by the Uniroyal Company at various Texas growers, and the Florida Research Station in Bradenton, Florida, as well as our partner company Classic Caladiums in Avon Park, Florida. Reproduction (in any form or fashion) of any of the Caladium Trials information is prohibited unless authorized by written consent from ABBOTT-IPCO, Inc., Dallas, Texas.

Please Note
Mention of pesticides, growth regulators etc. are by way of illustration only not an endorsement. The label is the law, therefore growers must follow label directions with all regulated materials. Furthermore, different cultivars respond differently to treatments therefore try a small percentage of your crop before applying a treatment to the entire crop. Mention of one product does not preclude the use or benefit of other similar products. Remember read the label and follow it.