Grow Time (From Rooted Cutting)
Calibrachoas in a quart container with one plant per pot take six to seven weeks; in a 1-gallon container with two plants per pot, 10 to 11 weeks; and in a 12-inch basket with four to five plants per pot, 11 to 12 weeks.
4.5-inch or quart containers require one pinch (during propagation) while gallon containers or baskets require one in propagation and one after planting. When growing baskets, trimming the branches once they grow over the edge of the baskets results in the most uniform and even plants. Use a viricide such as Virkon-S, RelyOn or Trisodium phosphate (TSP) viricides when pinching or trimming after at least every variety. An early application of Florel plant growth regulator at 350 to 500 parts per million (ppm) can be used to enhance branching or in place of the second pinch.
High-quality media with good porosity is critical to avoid root rot. Peat-based mixes, like Fafard 2 Mix or 1P Mix, or bark-based mixes, like Fafard4P Mix or 3B Mix work well.
Apply 200 to 250 ppm nitrogen (N), using a calcium-magnesium formulation of a balanced fertilizer with low phosphorus (i.e. 13-2-13, 14-4-14 or 15-5-15 Cal-Mag) or a more acidic ammonium-containing fertilizer (i.e. 20-10-20 or 20-9-20) if keeping the pH low is a challenge. Electrical conductivity (EC) should be around 2.0 to 2.5 mS/cm (SME) with pH between 5.4 and 5.8. Supplemental iron-chelate (Sprint 138 or 330) as a drench (4 ounces/100 gallons) is recommended to avoid iron deficiency related tip yellowing, especially under hot conditions and elevated pH (more than 6.0).
Calibrachoas should ideally receive more than 4,500 foot candles (more than 15 mols/day). On crops sold before April 1, night-interruption lighting is strongly recommended to bring plants into flower earlier and to get more even flowering across the series.
Initially, 68°F to 72°F days, 62°F to 64°F nights are ideal. The temperature can be lowered for the last four weeks of the crop.
Plant Growth Regulators
Spray with 2500 to 5000 ppm B-Nine plant growth regulator, 10 to 20 ppm Sumagic plant growth regulator or 5 to 10 ppm Topflor plant growth regulator. The key to achieve well-rounded and compact plants without stretching is a drench with Bonzi plant growth regulator three to four weeks before finishing. A drench with I ppm Bonzi could be enough for compact varieties like ‘Callie Rose’ or ‘Callie Light Blue’ while 3 ppm might be best for vigorous varieties like ‘Callie Bright Red’ or ‘Callie Star Rose.’
Calibrachoas are very sensitive to fungal root rot. Make sure to not over-water (especially at low temperatures), and keep pH between 5.4 and 5.8. Drench with broad-spectrum fungicide (Subdue Maxx plus Medallion fungicide combinations) as needed.
Scout for aphids and budworms. Flagship insecticide and Endeavor insecticide provide excellent control of aphids. Conserve insecticide and Dipel insecticide are effective in controlling budworm.