Lobelia Offers A Downy-Mildew-Resistant Option

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Lobelia 'Techno Heat Electric Blue'

Consider vegetative lobelia, such as the Techno and Techno Heat series from Syngenta Flowers, as a vivid and versatile alternative to Impatiens walleriana. The two series give consumers a long-lasting and low-maintenance color show in containers, combos and borders. Both Techno and Techno Heat deliver award-winning garden performance.

For spring and summer sales, we recommend lobelia for all regions of the U.S. and Canada, in shade or part-shade. Lobelia is also well suited for fall and winter use in the southern regions of the U.S. The Techno and Techno Heat series are early to flower and day-length neutral, working well for all turns in 4- and 6-inch programs.

Lobelia Propagation Tips

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 is ideal. Fertiss and Ellepot are common choices. Keep pH at 5.6 to 6.2, and test media EC and pH about three weeks after sticking. Adjust as needed.

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

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

Misting: 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 two to two-and-a-half 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 allow root development.

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

Plant Growth Regulators: Spray B-Nine plant growth regulator at 2,500 ppm or Sumagic plant growth regulator at 1 to 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.

Fungicides: Spray for Botrytis control at day two and day nine, alternating between Daconil ULTREX and Heritage. Drench with a broad-spectrum fungicide (Subdue MAXX plus Medallion fungicide combinations) three to three-and-a-half weeks after sticking to maintain a healthy root system.

Lobelia Finished Production Tips

Grow Time (from rooted cutting): A lobelia in a quart container with one pinch per plant (ppp) takes six to seven weeks of grow time. In a gallon container with two ppp, grow time is estimated at eight to nine weeks. Lobelias in 12-inch baskets with four to five ppp take 10 to 11 weeks of grow time.

Pinch: One pinch, ideally done in propagation, is enough for small and midsize pots. Trailing types will benefit from a second pinch a few weeks after transplant. The second pinch is not as crucial for Techno Heat upright types. When pinching, use excellent sanitation, including viralcides like Virkon-S, RelyOn or Trisodium phosphate.

Growing Media: High-quality media with good porosity is critical for best growth. Peat-based mixes or bark-based mixes can work well.

Fertilizer Rate: Apply 200 ppm N using Cal-Mag fertilizers (i.e., 13-2-13, 15-5-15, 14-4-14, etc.) for more compact growth and neutral pH. Use high ammonium and phosphorus-containing fertilizers (i.e., 20-10-20, 15-15-15, etc.) for softer growth and to lower pH. EC should be between 1.8 to 2.2 mS/cm (SME), with a pH between 5.8 and 6.2. Avoid letting plants get bone dry.

Light: Lobelias should ideally receive more than 4,500 foot candles (15 mols/day). Also, faster and improved flowering occurs when daylength is greater than 12 hours.

Plant Growth Regulators: Spray with 2500 ppm B-Nine plant growth regulator or 5 to 10 ppm Sumagic plant growth regulator to keep plants under control. Bonzi plant growth regulator drenches at 1 ppm also work well three to five weeks before sale.

Insects And Diseases: For lobelia, thrips and thrips-vectored diseases, such as impatiens necrotic spot virus (INSV) can cause problems. Flagship insecticide, Avid miticide/insecticide and Conserve insecticide are effective in a thrips management program. Test suspicious-looking plants immediately. Symptoms of INSV on lobelia include spotted and necrotic leaves, similar to high salt damage. Subdue MAXX, Heritage and Daconil ULTREX fungicides provide protection against foliar and root disease.    

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