Grower Facts

Delphinium Guardian (Delphinium elatum)

Germination
Use a well-drained, disease-free, soilless medium with a medium initial nutrient charge and a pH of 5.8 to 6.2. A medium cover of coarse vermiculite is strongly recommended. Germination takes 7 to 8 days.
Plug Production
Media：Use a well-drained, disease-free, soilless medium with a medium initial nutrient charge and a pH of 5.8 to 6.2.
Sowing：A medium cover of coarse vermiculite is strongly recommended. Germination takes 7 to 8 days.
Temperature：Maintain 68 to 70°F (20 to 21°C) through germination and cotyledon emergence.
Delphinium in general does not show uniform germination. Seeds within a plug tray germinate over a 3 to 4-day window. Leave the plug trays in the germination chamber for an additional period of 2 to 3 days after the first sign of germination for best results. Move the plug trays out of the germination chamber at “open cotyledon” stage.
Stage 2 and 3 plugs can be grown at 65 to 70°F (18 to 20°C) days and 60°F (15°C) nights. A week before transplant (end of Stage 4), plugs can be grown at cooler temperatures for toning. Daytime temperatures of 65°F (18°C) and nighttime temperatures of 60°F (15°C) are recommended.
Light：Light is not required for germination, but will be an added advantage.
Humidity：Maintain 95 to 97% relative humidity until cotyledons emerge. Chamber germination will result in better results. Maintaining high humidity during Stage 1 (sow to radicle emergence) is critical for germinating this crop.
Fertilizer：Begin fertilizing at week 3 with 50 ppm N twice a week. After a week, increase the nitrogen rate to 100 ppm twice a week until finish. Maintain EC less than 0.75 until week 3. Increase EC to 1.0 until finish for the best results. A pH range of 5.8 to 6.2 is optimal during plug production.
Growth Regulators：Growth regulators are not recommended for cut flower plug production.
Tip：It is important to avoid transplanting plugs that have become rootbound, as they may flower prematurely.

Growing On to Finish
Density：Guardian delphinium has a recommended density of 4 plants/net ft.2 (40 plants/net m2) for an Autumn transplant.
Support Netting：One layer of support netting using 6 in. by 6 in. squares (15 cm by 15 cm) is recommended for all production locations.
Height：Guardian delphinium height ranges from 30 to 39 in. (75 to 100 cm). Guardian plants will be taller when grown under greenhouse conditions, and somewhat shorter under field conditions.
Media：Use a well-drained, disease-free media, with medium initial nutrient charge and a pH of 5.8 to 6.5. It is advisable to disinfect the production location at least once per year, prior to transplanting.
Temperature：Maintain 54°F (12°C) during the first 2 weeks after Autumn (Fall) transplant. Raise day temperature to 59° F (15°C) after 2 weeks. Maintain minimum night temperature of 60°F (15°C) and day temperatures of 65 to 70°F (18 to 21°C). Under northwestern European conditions, temperatures may rise during sunny days when light levels increase. Be aware of leaf burn in periods of variable weather (alternating from cloudy to sunny days).
Light：No supplemental lighting is required.
Fertilizer：When growing in the greenhouse, begin fertilizing 1 week after transplant with 150 ppm N, applied once a week. If grown outside, additional fertilization may be required. Maintain an EC of 1.5 and a pH of 5.8 to 6.2 after transplant until finish.
Shading：50% shade cloth or an equivalent amount of shading compound may be necessary during periods of high light or high temperature.
Harvest Maturity：Guardian delphiniums should be harvested when approximately one-third of the flower spike exhibits color.
Postharvest Temperature Management：Precool to 33°F (1°C) prior to shipping for best postharvest quality and vase life.
Ethylene Sensitivity：Guardian delphiniums should be treated with an ethylene inhibitor prior to shipment.

Common Problems
Insects: Watch for fungus gnats during plug production. Western Flower thrips can spread Tospovirus. Leaf Miner occasionally tunnel through delphinium leaves.
Diseases: Pythium root rot: Can be a problem during Stage 1 and 2 of plug production, and also after transplant.
Powdery mildew: Can be a production issue during vegetative or reproductive growth.