Delphiniums are perennial-growing, late-spring blooming plants that are a cottage garden favorite. The tall varieties of delphiniums grow to between 6 and 8 feet tall and make for striking background plants. Dwarf varieties of delphiniums can grow between 3 and 4 feet tall and can be planted along borders. They are hardy in the USDA Zones 3 to 7 and are indigenous plants to Europe. Plan on starting delphinium seeds indoors from September through October, for spring planting.
Fill up a seed-starting tray, or planting packs, with a sterilized seed-raising mix until the mix is approximately 1/4 inch from the top of the rim. If you're using mix that has not been sterilized, see the tips section for information on sterilizing germinating media.
Pack down the mix, using the bottom of a glass, a large metal spoon, the bottom of a 3- or 4-inch pot or your hands.
Mix together a multipurpose fungicide with water as specified on the product's label. Saturate the germinating media with the water and fungicide mixture. Let the water fully drain away before proceeding. The use of a fungicide will help prevent any fungal diseases from killing the delphinium seedlings.
Create shallow 1/8-inch-deep rows, using the long edge of a 12-inch ruler, if planting the seeds in a seed-starting tray. Plant one to two delphinium seeds approximately 1 1/2 to 2 inches apart in the rows. If planting in planting packs, plant one to two seeds in each cell. Cover the delphinium seeds with no more than 1/8 inch of germinating media.
Cover the tray, or planting packs with a sheet of glass, or stretch out a layer of clear plastic wrap and secure in place with a rubber band, if necessary. Place the tray or planting packs into a refrigerator for seven days.
Remove the plastic wrap or sheet of glass after the allotted time has passed. Place the tray or planting packs near a south- or west-facing window, out of direct sunlight. Keep the soil in the planting packs or tray moist but do not water so often the soil remains soggy wet. Germination of delphinium seeds will typically begin in three to four weeks.
Transplant the delphinium seedlings into peat pots or 4-inch pots when they each have several pairs of leaves. Keep the seedlings moist and in a well-lit location in your home until the last chance of frost has passed, then you can plant them in their permanent location outside.