Hi- Welcome to our world of dahlias! We grow over a 1000 dahlias plus beds of new seedlings each year. Mostly our garden is grown for our enjoyment but I do sell cut flowers as well.
DAHLIA GROWING INSTRUCTIONS:
Wait until all danger of frost is past before planting. (Vanc.Island is normally end of April) If you bought dahlias early, keep them cool in a garage or if you want to start them early, lightly cover with soil to encourage sprouting. This can be done up to 2 months before planting but I usually only keep them a month inside or I spend too much time hardening them off. Dahlias grow their best with 6 to 8 hours of direct sunlight, in rich, well-drained soil and slightly acidic. If you have a heavier soil, add in sand, peat moss or add well aged manure.
Plant about 2 to 3ft. apart. You can use bone meal into the planting hole and a tbsp. of fertilizer such as 20-20-20 or 6-8-6 or use organic starters like alfalfa pellets. Plant tubers with the “eyes” facing up, about 6 inches deep. Seaweed can be added during the winter or compost to give young plants the nitrogen they need but too much nitrogen will give you tall, green plants with little blooms. You can lightly water if very dry. Pinch the center out of the plant at 4 to 5 pairs of leaves. Fertilize monthly but watch your leaves as they are a good indicator as to what you might need. Soil on the west coast is robbed of minerals during the rainy season so I normally sprinkle epsom salts around my plants if I see yellowing leaves. You can use any fertilizer that you would to grow good tomatoes. Dahlias will bloom more with a high middle number fertilizer whether it's granuals or liquid.
Label your dahlias at planting time and later in the season before you cut it down, you can move that label to the bottom of the plant before lifting.
Tie stems to the stakes as the plants grow usually about 2ft and 4ft or zig zag heavy string to support them later. Dahlias start blooming about 8 weeks after planting, starting in mid-July- remember the more you cut them the more they will bloom and it keeps the plants tidy. For more instructions visit Fundamentals of Growing Dahlias – The American Dahlia Society