February 2012 Culture

Perennial Solutions: Caladium ‘Peppermint’ By Paul Pilon

Caladiums make a great addition to any perennial program. With their interesting and colorful foliage, caladiums provide instant color to retail displays and fit perfectly with the ‘color sells’ philosophy in today’s marketplace.

Breeding and selection efforts by Robert Hartman of Classic Caladiums in Avon Park, Fla., have brought many interesting and improved cultivars to the marketplace. Their recent introduction ‘Peppermint’ is no exception. ‘Peppermint’ becomes more colorful as it matures. This new strap-leaved (lance-leaved) introduction has mostly white foliage with rose-red blotches as the leaves first emerge; however, the foliage characteristics change as the plant ages with mature leaves displaying a dark-rose red background with creamy white venation and a narrow green margin.

‘Peppermint’ has an intermediate growth habit and reaches 10 to 12 inches when grown as a potted plant and 12 to 18 inches tall in the landscape. Although this column typically features various types of perennials, keep in mind that caladiums are tropical plants and are not cold hardy below USDA Hardiness Zone 9. In Zones 8 or lower, caladiums do not survive the cold winter temperatures and the tubers must be lifted out of the ground each fall.

In the Northern United States, caladiums are commonly grown and marketed as potted plants or in combination containers, but they can be sold as perennials in USDA Hardiness Zones 9 to 11. Many perennial growers are adding caladiums and other tender perennials or tropical plants to their production lines to supplement their current offerings. With its interesting foliage coloration, ‘Peppermint’ provides a colorful presence in retail settings and would make a great addition to potted plant programs.

Propagation

‘Peppermint’ is a patented cultivar (PP 22,214) and any propagation without a license is strictly prohibited. It is not economical or practical for growers to propagate caladium, grow the tubers to maturity, and then produce a finished crop.

Production

Caladiums require at least six weeks of curing from the time they are harvested until they can be delivered to growers. They are grown from tubers; however, in the industry they are commonly referred to as bulbs. The more time the tubers are cured, the quicker they will force in the greenhouse. Upon receipt, open and unpack the boxes and let the tubers sit at room temperature in some type of vented trays for one to two days before planting. They should be kept above 55° F or cold injury to the tubers could result.

Many growers remove the terminal bud or de-eye the bulb prior to planting. De-eyeing is a method that results in more compact plants with more shoots/leaves per tuber than plants that have not been de-eyed. Additionally, de-eying decreases the forcing time by up to two weeks. Growers can de-eye caladiums by cutting out the dominant buds using a small knife or puncturing and destroying the terminal bud using a nail. After de-eying, it is important to let the bulb cure (dry and heal) for at least one day before potting
otherwise disease may enter the bulb after potting. Bulbs/tubers that are already de-eyed are available from the suppliers.

‘Peppermint’ is commonly grown in 4-inch or larger sized containers. The number of bulbs needed varies with container size, the size of the bulb, customer specifications, and the price point of the product. Small container sizes, such as one quart containers, usually contain one bulb each, whereas larger container sizes, such as one gallon pots, often contain up to three #1 size or six #2 size bulbs in each pot.

Caladium performs best when they are planted into a course, well-drained growing mix. Plant the tubers with the rounded side down and the sprouts (eyes) up. After planting, there should be approximately 1.0 inch of growing mix over the top of the tubers.

The growing mix should be kept moist until the bulbs have sprouted. After emergence, decrease the moisture levels slightly, keeping the plants uniformly moist until the plants are near the desired plant size. As they approach the finished size, let the media dry out slightly between waterings. Avoid drying them down too much or leaf edge burn is likely and in severe cases the plants may go into an early dormancy.

Maintaining adequate temperatures for uniform emergence and growth is the primary factor to successfully growing uniform caladium crops. It is best to keep the temperatures above 70° F during production. Newly planted caladium emerges and grows most rapidly when the soil temperatures are maintained at 80 to 85° F. Once the shoots have emerged and average 2 inches in height, the greenhouse temperatures can be reduced to 70 to 75° F for the remainder of production. The optimal light intensity for Caladiums is between 2,500 and 5,000 foot-candles.

Caladiums have moderate fertility requirements. However, they perform best when nutrients are applied intermediately as opposed to being grown under constant liquid fertilizer programs. Healthy plants can be produced when 100- to 200-ppm nitrogen is applied weekly or with every other irrigation. The acceptable pH range is 5.5 to 6.5.

Growth regulators are often applied to caladiums that are grown at high plant densities or in small containers. A good starting point is to drench them with paclobutrazol at 8 ppm when the shoots have emerged, but before they leaves are unfolded (approximately two to three weeks after potting). Some growers successfully maintain plant size using foliar applications of daminozide at 2500 ppm as needed at five- to seven-day intervals or make a 30-ppm spray paclobutrazol application near the end of the crop cycle to hold plants until they are sold.

Insects and Diseases

There are usually not any significant problems associated with insects. However, several plant pathogens have been known to attack Caladiums. Some of the most serious diseases including Erwinia, Fusarium and Rhizoctonia commonly attack the tubers while other diseases such as Pythium and Phytopthora may attack the root systems. Any tubers with discolored areas or white chalky substances on them should be discarded prior to potting. Many growers apply a preventative drench using broad-spectrum fungicides such as Heritage, Subdue Maxx + Medallion, or Subdue Maxx + Cleary 3336 between potting and emergence to reduce the incidence of pathogens. Additional drenches may be applied as needed.

Temperature and Scheduling

The main factor influencing the timing of caladium ‘Peppermint’ is temperature. Keep in mind they are tropical plants and perform best with warm temperatures. Never allow the temperatures to fall below 65° F during production. To optimize plant growth, maintain day and night temperatures above 70° F. The time to finish is determined by the planting date and the size of the container they are being grown in. For late January and early February plantings, it takes approximately eight to nine weeks to finish quart-sized containers and 10 to 12 weeks for 6-inch or larger container sizes. Late February through March plantings take approximately six to seven weeks for small containers and eight to 10 weeks for large container sizes. Planting caladiums in April or later results in slightly quicker finishing times: four to five weeks for 4-inch and six to eight weeks for 6-inch or larger sized pots.

Availability

Caladium ‘Peppermint’ is a patented introduction from Classic Caladiums (www.classiccala diums.com). Tubers are available from Classic Caladiums and the exclusive licensee ABBOTT IPCO, Inc. (www.abbott-ipco.com). All tuber sizes (#2, #1, and Jumbo) are available from both companies. Classic Caladiums and ABBOTT IPCO also offer ‘Peppermint’ in prefinished containers (4 and 6-inch pots), which often reduces the finish times down to two to three weeks for growers.