Cultural Information
petunia Frillytunia, Horizon, Rapide, Prism

Plug Production
Sowing/Media: Use a well-drained, disease-free, peat-based plug medium with pH 5.5 – 5.8 and media EC <0.75 mmhos (saturated paste). Use pelleted seed for best sowing results. No covering needed.

Germination (Stages 1 and 2): Keep soil uniformly moist, not saturated, then reduce once cotyledons are open. Do not bury the seed! Soil temperature should be 72 – 75°F. Light levels should be <2500 footcandles, and is beneficial for germination.

Stage 3: Soil temperature should be 68 – 72°F. Dry down soil before watering again once cotyledons are open to improve rooting, control floppiness, and keep seedling growth even. Keep light levels around 3000 footcandles, and use HID lights with daylength extension to speed up growth and flowering during low light periods. Night-interruption lighting can also be used during short days to initiate faster flowering, as petunias are considered a long-day plant. Feed every other watering with 100 – 150 ppm N from 15-5-15, 17-5-17- or 20-10-20 (high light conditions only). Keep media pH 5.5 – 5.8, definitely <6.5, and media EC 1.25 – 2.0 mmhos (saturated paste).

Stage 4: Soil temperature can be lowered to 62 – 65°F. Dry down between waterings. Keep light levels around 3000 footcandles, and feed as needed, but use 13-2-13 for more tone.

Plant Growth Regulators: Spray with B-Nine (1000 – 2500 ppm), A-Rest (3 – 7 ppm), Bonzi (5 – 30 ppm), or Sumagic (2 – 15 ppm) as needed to control growth. Do your own trials to avoid overdosing, as vigor of varieties, weather conditions, and cultural practices directly affect how much growth regulator to use.

Crop Time: 4 – 6 weeks for 512 plugs, 5 – 7 weeks for 288 plugs, depending on light levels and use of HID lights.

Common Problems: Pythium, Phytophthora, Botrytis, upper yellow leaves – high media pH (>6.5) or low iron, uneven growth – moisture management (too wet too long) after germination is finished, lower yellow/purple leaves – low feed.

Growing on to finish

Container Size: Large cell packs to 6-inch pots

Media: Transplant into a well-drained, disease-free, peat-based growing mix with pH of 5.5 – 5.8 and EC <1.5 mmhos (saturated paste). Do not bury plugs!

Temperatures: Keep soil temperatures 65 – 68°F for rooting out, then lower to 62 – 65 F for growing on. Avoid growing cooler than 60 F before flowering, as cool temperatures will delay flowering.

Light: Maintain light levels 3000 – 5000 footcandles. HID lights can be used for daylength extension, which is beneficial for compact growth and faster flowering during low light periods. Night-interruption lighting can also be used for faster flowering during short days, but may result in stretched plants.

Irrigation and Fertilization: Practice a good wet/dry cycle for best rooting and height control. Petunias can tolerate a little bit of wilting. Feed 1 – 2x/week with 150 – 200 ppm N from 15-5-15, 17-5-17, or 20-10-20. Keep media pH 5.5 – 5.8, definitely <6.5, and media EC 1.25 – 2.0 mmhos (saturated paste).

Plant Growth Regulators: Use sprays of B-Nine (2500 – 5000 ppm), Bonzi (15 – 30 ppm), or Sumagic (5 – 15 ppm) as needed. Once up to size and flowering, use a drench of Bonzi (2 – 5 ppm) or Sumagic (1 – 2 ppm) to control growth. Adjust rates and frequency of application based on vigor of varieties, weather conditions, and cultural practices. Do your own trials, especially with drenches, to avoid overdosing.

Common Problems: Pythium, Phytophthora, Botrytis, upper yellow leaves – high media pH (>6.5) or low iron, lower yellow/purple leaves – lack of feed, slow flowering – failure to provide long days with lighting.

Crop Time: 3 – 5 weeks, depending on plug and container size, light levels, daylength, and temperature.