Planting Method of Delphinium
In the bleak winter, the swaying delphinium in the garden always brings a touch of brightness. This herbaceous plant, resembling a flying swallow, is favored for its unique blue-purple inflorescence. However, many gardening enthusiasts are puzzled by its overwintering care. This article will systematically analyze the entire planting process of delphinium and focus on uncovering its overwintering secrets.
The Four Steps of Delphinium Sowing
Golden Sowing Time Selection
The sowing timing directly affects the germination rate. It is recommended to choose March to April or late August to early September when the day-night temperature difference is small. During this period, the surface temperature is stable between 15-22°C, which is especially suitable for seeds to break dormancy. In the northern regions, if choosing autumn sowing, ensure that sowing is completed 30 days before the first frost.
Seed Selection Techniques
When the bottom 1/3 of the spikelet turns brown, the seeds can be harvested, indicating that the maturity of the seeds is over 80%. Use the dry screening method: spread the seeds on white paper and gently brush off the flat seeds, retaining the plump seeds with a diameter of ≥2mm. After treatment, the seeds should be dried in a cool and ventilated place for 72 hours to reduce the moisture content to below 12%.
Scientific Substrate Mixture Ratio
The ideal planting substrate should be composed of peat soil: perlite: decomposed pine needles = 5:3:2, with a pH value between 6.0-7.0. For every cubic meter of substrate, 200g of slow-release fertilizer (NPK 14-14-14) can be mixed in, and the substrate should be disinfected by pouring with hot water at 50°C before sowing.
Accurate Sowing Technique
Use the drill sowing method, with a furrow depth of 2cm and a row spacing of 25cm. The sowing amount per square meter should be controlled between 3-5g, and after sowing, cover with 0.5cm of fine vermiculite. Maintain the substrate moisture at about 60%, and the seedlings will emerge in 7-10 days.
Delphinium Overwintering Care Guide
Cold Resistance Mechanism Analysis
The underground rhizome of delphinium is rich in antifreeze proteins, allowing it to survive in temperatures as low as -15°C. The critical cold tolerance point of its above-ground parts is -5°C. If the night temperature continuously remains below this value for more than 72 hours, protective measures need to be initiated.
Three-Level Cold Protection Strategy
Level 1 protection (0 to -5°C): cover with 5cm thick pine needles. Level 2 protection (-5 to -10°C): build a 60cm high windbreak shed. Level 3 protection (below -10°C): wrap with cold-resistant non-woven fabric + double insulation with plastic film.
Winter Water and Fertilizer Management
Water thoroughly once a month in the morning at 10 o'clock on sunny days, with the water temperature difference from the ambient temperature not exceeding 5°C. Apply high-potassium fertilizer (NPK 5-15-30) once a month, with an amount of 1/3 of the growing season.
Through scientific sowing management and graded overwintering protection, even in the severe cold regions of the north, delphinium can safely overwinter. Mastering these core techniques, you will be able to enjoy the visual feast brought by this elegant plant year after year. It is recommended to adjust the care plan according to the local climate characteristics and, if necessary, consult a professional gardener for on-site guidance.