Delphinium Production Tips
Perennial production tips from Takii.
August 10, 2011
The Aurora F1 delphinium series from Takii & Co., LTD is a stunning elatum type. Aurora has densely packed spikes filled with large flowers that provide brilliant, long-lasting color, both as a perennial garden plant and as a cut flower. The showy flowers have outstanding consumer appeal and are irresistible for avid gardeners. Aurora will grow 3 to 4 feet tall and produce uniform spikes on sturdy stems. The series is comprised of six varieties - Blue, Deep Purple, Lavender, Light Blue, Light Purple and White.
Time from sowing to flower is approximately 18 weeks, about a 6 to 8 week shorter crop time than the older open-pollinated types. Cutting the plant back to the ground after its first blooming cycle will allow it to re-cycle and flower again in about 6 to 8 weeks.
Aurora is perfect for 1- or 2-gallon pots in garden centers. Ideal sales time is when the first florets begin to open on the flower spike. Aurora can even be grown year-round in cool climate areas because of the earliness in flowering.
Seeds will take 10 to 15 days to germinate at a temperature of 60°- 68°F/15°-20°C. Sow in a 288 or 200 plug tray. The optimum plug media is well-sterilized peat moss:perlite: vermiculite at ratios 1: 1:3 or 2:0:3 with pH 5.5 to 6.5. Seeds must be covered as dark is required. Keep wet until germ/root emergence. Pre-cool treatment of 45°F/7°C, wet and dark for 2 days will help the uniform germination under high temperature conditions such as summer sowing. Plug finish time is 5 to 6 weeks, with optimal growing temperatures of 60°-78°F/15°-25°C.
Keep EC at a low level before true leaves appear. Maintain even moisture in the medium, and avoid dry soil and excessively wet soil. Delphiniums are very sensitive to root-rot diseases. Fertilizer can be applied as necessary if leaves look deficient, but avoid excessive fertilizer. Young seedlings are very sensitive to high temperature. Avoid high humidity and high temperatures during plug production.
Keep conditions cool (minimum 45°F/7°C) and moderately dry. Slowly grown seedlings produce better finished plants. Maintain an average of 77°F/25°C days and 60°F/15°C nights until 1 to 2 true leaf stage, then lower to 68°F/20°C days and 50°F/10°C nights to prevent premature flower initiation under high-temperatures. Check the roots carefully in the later stage of plug culture, as root-bound plugs may result in weaker growth.
Larger seedlings are preferable for fall plantings to avoid premature flower initiation. Suitable temperature is 77°F/25°C days and 60°F/15°C nights. After transplant, water well to establish the root system. If roots dry even once, growth will be very poor. Roots also need good aeration to discourage root rot.
Induce flowering with temperatures higher than 60°-35°F/15°-18°C Extending daylength to 16 hours helps flowering but is not required for flower initiation. Minimum night temperature should be 55°-60°F/13°-15°C for finishing.
Watch for crown rot, bacterial leaf spot, powdery and downy mildew, thrips, aphids and spider mites.