October 2003

Robusta Jumbo Cyclamen By Jeannine R. Bogard

Robusta answers the call for full, colorful crops adaptablefor both home and garden with larger leaves and huge flowers, which will satisfythe needs of floral buyers in addition to stimulating impulse sales at retail.Robusta’s strong and full-bodied habit will easily fill out 6- to 71/2-inchcontainers, while the proportionally large blooms create a prolific bouquet ofcolor. Seven colors make up the series: Fuchsia, Purple, Rose, Salmon, Scarlet,White and Wine.

Bred for the large-container market, Robusta blooms 2-3weeks later than the Sierra series, so program Robusta for mid- to late-seasonsales (late November through February). Because Robusta’s habit is larger thanstandard-sized cyclamen, there are a few nuances to growing these super-sizedplants that differ from traditional culture.

Growing on

Robusta requires partial shade to filtered sun. During thebright hot days of summer there is a risk after transplant for the plant togrow too quickly and develop large leaves too soon in the growth cycle. Toavoid excessive leaf development during summer months, it is necessary to growRobusta with modified fertility levels.

Potassium. Typically,cyclamen are initially grown at a nitrogen:potassium ratio of 1:1 and graduallyincreased to 1:2. During the last third of the Robusta growing cycle increasenitrogen:potassium ratios to 1:3. With Robusta’s larger habit, potassium takeson a greater role in producing a higher-quality plant.

Potassium is important in the growth of cyclamen becausedeficiencies will result in soft growth, and plants are more susceptible todamage. Potassium is also important in translocating sugars and starches to thegrowing tips. Low potassium levels can result in stunted plants. As a generalrule, plants normally absorb potassium during the first half of their growthcycle. Peak demand for potassium during cyclamen development occurs at bud set.Plants grown with reduced levels of potassium run the risk of reduced flowerquality and overall shelf life. Optimum potassium levels will increase theoverall flower count on cyclamen, thus creating beautiful bouquets of blooms.

The nitrogen:potassium relationship is important for otherreasons as well. Potassium will counter many of the negatives of nitrogen.While nitrogen stimulates rapid, soft growth, potassium counters by promotingfirmer tissues. And while nitrogen may increase sensitivity to diseasepressure, potassium increases disease resistance. To anyone who has growncyclamen, the importance of promoting strong healthy plants cannot be overemphasized.

Water. Moisturemanagement is important in producing a strong plant. Irrigate Robusta when themedia has changed color from a dark black to a medium brown. After irrigation,the media should be wet to the touch, but not saturated. Watering early in theday allows the foliage to dry before nightfall and prevents crown rot. Water isimportant in the uptake of potassium into the plant. The diffusion of potassiumis a slow process and occurs through the film of water that surrounds theroots. Crops kept too dry can appear stunted. However, once absorbed into theplant, potassium is readily translocated through the plant.