August 2005

Crop Culture Report: Lobelia Hot By Nadine Malih

The Lobelia Hot series, bred by Westhoff in Germany, was introduced to the North American market 11?2 years ago through an exclusive marketing agreement with Cohen Propagation Nurseries, which holds exclusive rights for mother stock and cutting production. Five great colors were offered in the first year: ‘Hot Arctic’ (light blue with white eye); ‘Hot Lavender’ (light pink); ‘Hot White’ (white); ‘Hot Waterblue’ (light blue with a newly improved growth habit) and ‘Hot Whitespot’ (light blue with white eye — same color as Arctic but with a more upright growth habit).

For the new season and due to popular demand two new colors have been introduced: ‘Hot Blue’ (dark blue) and ‘Hot Blue Eye’ (dark blue with white eye).

All varieties have excellent growth habits and produce immaculate baskets. The concept of the lobelia Hot series is that these are very heat-tolerant varieties. All varieties in the Hot series will not only survive the summer but will be in full bloom throughout the entire summer, even in full sun. All varieties of this broad green leaf series will grow 8-12 inches tall.

In the second year of production Cohen sold more than 1 million cuttings of this annual and the first experience and impression from customers is that the varieties truly are heat tolerant and can fit wonderfully in spring-summer sales.

Propagation

Since lobelia is difficult to start from seed, unrooted cuttings of Hot, produced from certified stock kept in Israel, are available year-round. Lobelia Hot is sold by brokers in North America.

A rooting hormone may provide best results during propagation. Soil temperature during propagation should be maintained at approximately 70-75° F, and bottom heat will enhance root development. Frequent misting will prevent wilting.

Rooting usually takes 8-10 days under maximum light but with a temperature not exceeding 82° F. Also, propagating under high light will prevent future stretch, as will transplanting cuttings as soon as possible.

Growing on

Lobelia Hot can be produced in 6-inch pots, containers or baskets. ‘Hot White’, ‘Hot Waterblue imp.’ and ‘Hot Blue’ are more compact and can also be produced in 4-inch pots. Six-inch pots of lobelia Hot will finish in about 6-8 weeks, and baskets will finish in 9-11 weeks.

Maintain temperatures at 75-82° F with humidity of 90-95 percent for optimal rooting. Growing temperature should remain at 57° F during the night and 66° F during the day. Light levels should remain around 5,000-8,000 foot-candles, while a soil pH of 5.6-6.2 should be maintained. One thing to really keep a lookout for is soil moisture. Don’t keep soil too moist, as stress from moisture combined with the necessary high light levels may cause leaf burn.

For the best branching, two pinches — one after rooting is complete and one after the plant is established — will work best. Also, for the best results apply B-Nine (daminozide, Chemtura Corp.) to young plants to keep them compact. Hot is not susceptible to any out-of-the-ordinary pests or diseases. However, watch for pests and diseases typical to lobelia, such as spider mites, thrips and Botrytis.