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.
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 viricides like Virkon-S, RelyOn or Trisodium phosphate (TSP).
High quality media with good porosity is critical for best growth. Peat-based mixes, like Fafard 2 Mix or 1P Mix, or bark-based mixes, like Fafard 4P Mix or 3B Mix work well.
Apply200 parts per million (ppm) nitrogen (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. Electrical conductivity (E.C.) 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.”
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-Nineplant 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 & 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 insecticides provide protection against foliar and/or root disease.