Culture Report: Lobelia Hot+ Series By Bart Hayes

This next generation of heat-tolerant lobelia offers larger flowers and more uniform plant habits.

The Hot+ series of lobelias are an improved version of the classic series that redefined lobelia. This exceptionally heavy-branched, mostly mounding series takes all of the best attributes of the original Hot series of lobelias — like incredible heat tolerance and heavy flowering — and makes the flowers larger and brighter. They are ideal for 4-inch pots, with inclusion in combination and hanging basket programs giving amazing results as well. The season-long flowering and uniform habit make it easy to produce for growers and give home gardeners better performance.


Hot+ cuttings can be stuck into a 105-count tray filled with well-draining, loose-filled propagation media or an engineered soil plug for best results. They hold up best at a steady temperature of 68 to 76° F. It’s important to mist only enough to keep the soil moist and humidity high until root initials are visible.


Using KIBA rooting hormone at 100 ppm is recommended to enhance the rooting speed and uniformity of lobelia.


A light pinch is recommended once the plants have rooted to the side of the propagation cell and have started to produce new growth, which usually occurs 17 to 20 days after sticking. This will enhance branching and help control the growth habit of the Hot+ series.


Lobelia plants can be transplanted once they are very well rooted into a well-balanced, well-drained soilless media. Keep a steady temperature range of 68 to 72° F for the soil throughout the rooting period, then gradually reduce the temperature to around 62 to 66° F for finishing. Cooler temperatures can be used for additional height control, if needed, but keep in mind it will likely take additional time to finish.

After the lobelia are initially established, continue to water plants early in the day to allow foliage to dry and allow the soil to dry slightly in between watering for best results.


Good water management and cooler growing conditions — 58 to 62° F — will help restrict excessive growth and result in overall better quality. If more control is needed for your lobelia production, B-Nine (daminozide) at 1,500 to 2,500 ppm can be used to maintain proper growth. An additional cut-back or shear can be used for growth control too, but it can take up to three weeks for the plants to rebloom.


Supplemental lighting is a great option when growing the Hot+ series. It will not only encourage early flowering but will also improve the overall plant performance.


Fertilize lobelia at a medium rate to allow for healthy growth; for example, use 150 to 200 ppm nitrogen of a 20-10-20 option. An EC between 1.0 and 1.3 (using a 1:2 extraction method) and a pH between 5.6 and 6.4 is recommended. Be sure to regularly check soil pH and EC as part of a comprehensive plant health management program. Also, flushing with clear water will help to avoid excessive salt build up in the soil.


The lobelia Hot+ series is best used in 4-inch pots and quarts, hanging baskets and combination planters.


Although selected for increased tolerance, lobelia can be sensitive to high soil pH nutrient deficiencies. The use of a supplemental chelated iron or petunia-specific fertilizer may be used to prevent these issues from arising.


Finish times for the Hot+ series depend on pot size and the number of plants per pot. All grow times given are based on the number of plant plugs from a 102-cell tray transplanted into the specified pot size. One plant per pot in a 4.5-inch pot will take six to eight weeks to finish; a 6.5-inch pot with two plants per pot has a grow time of about seven to nine weeks; and a 10-inch pot with three to four plants will take the longest at 10 to 12 weeks for finishing.

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Bart Hayes

Bart Hayes is sales manager for Westhoff/Westflowers. He can be reached at

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