Lobelia: Propagation Tips

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Lobelia Techno Heat series

Upon Arrival

Stick relatively quickly and get cuttings hydrated as soon as possible. Only store unrooted cuttings overnight in a cooler if necessary. Cuttings can easily dehydrate.

Rooting Time

Unrooted cuttings typically take about three and a half to four weeks to root in a 105-sized plug. The “heat” type lobelias (i.e. Techno Heat varieties) root faster than most traditional “non-heat” types (i.e. Techno Blue).

Growing Media

High-porosity media like Fafard 1P Mix is ideal. Fertiss and EllePot are also common choices. Keep pH at 5.6 – 6.2, test media E.C. and pH about three weeks after sticking and adjust as needed.


Lobelias do need to be pinched. Be sure to use good sanitation. Cuttings should be well-rooted before pinching.


Media temperatures of 72–74°F are ideal. Once the cuttings are fully rooted, the temperatures can be lowered to control growth.


Spray CapSil one day after sticking to reduce wilting. Do not quit misting too soon and keep humidity high. Lobelias thrive best when misted lightly until adequate rooting occurs, which should be at about 2 to 2.5 weeks. Gradually reduce night misting from day two through day seven. Purpling of cuttings can occur when lobelia are taken off of mist too early before they have adequate roots or when the media is staying too saturated to prevent root development.


Apply 100 parts per million (ppm) nitrogen (N) when cuttings start rooting, using a calcium-magnesium formulation of a balanced fertilizer with low phosphorus (ex. 14-4-14,13-2-13 or 15-5-15 Cal-Mag™). Fertilize daily with 150 ppm nitrogen (N) when fully rooted.

Plant Growth Regulators

Spray B-Nine plant growth regulator at 2,500 ppm or Sumagic plant growth regulator at 1 – 2 ppm (make sure to apply lightly). It’s also worth trialing Florel plant growth regulator at 350 ppm or Florel (350 ppm) plus B-Nine (1,500 ppm) as a combination spray about 12 days after sticking and before pinching


Spray for Botrytis control at day 2 and 9 alternating between Daconil ULTREX and Heritage. Drench with a broad-spectrum fungicide (Subdue Maxx plus Medallion fungicide combinations) 3 to 3.5 weeks after sticking to maintain a healthy root system.

Insects, INSV

Scout for thrips and signs of impatiens necrotic spot virus (INSV). Spray with Avid miticide/insecticide alternating with Conserve insecticide. Test suspicious looking plants immediately. Symptoms of INSV on lobelia include spotted and necrotic leaves, similar to high salt damage.

Karl Trellinger (karl.trellinger@syngenta.com) is a technical services specialist with Syngenta Flowers.

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