Growing great Dahlias
A word on tuber variation
Dahlias are grown from tubers. A tuber is part of the stem system of the plant that grows underground, it's root system will grow out of the tuber. To know if your tuber is viable (or if it will grow into a plant), you need to find eyes on the old part of the stalk (the very tip of the tuber). From the eye, an entire plant will grow. Inspect all newly purchased tubers carefully, just to make sure you've received something that has the ability to grow. Sometimes, eyes have already begun to sprout, making them extremely easy to find. Other times, they have yet to sprout, and you'll have to look very carefully for bumps on the stalk. Given time to warm up, they'll sprout too. Pictured on the right ( or below if using a mobile device) are two tubers that are both viable. One large tuber (Amber Queen) and a small tuber (Koko Puff). Koko Puff has a sprouted eye, or several sprouted eyes, while the larger tuber has yet to sprout. If you look carefully though, you can find bumps on the stalk.
Tubers come in a variety of sizes and shapes. Depending on the cultivar, tubers can be tiny, store poorly over winter (will shrivel easier) or be huge. Most growers will favour sending smaller roots, as it's less costly to mail, and in the end you'll have the same beautiful plant a large tuber would produce. What is important to remember- size isn't what counts. If it has a viable eye- you're good to grow!
As soon as you receive your package of dahlias- open the box! It is important to let them breathe, even if they won't be planted for a while.
1- Plant them in a pot with potting mix, and set them in a sunny place. Then transplant out in the garden when the soil is ready. The benefit of translating is your dahlia will have a longer season, and start blooming earlier.
2-Directly plant the tuber in the garden.
Tubers can be planted out into the garden when soil temperatures reach 15 C. This is early to mid May in my growing region (zone 5). Dahlias are heavy eaters. They would benefit from adding a dose of composted manure to their planting site. They like full sun, and good drainage. Add your compost and loosen the soil. Dig down 6 to 8 inches, and lay your tuber down, eye facing up. If planting multiple, they like 12-18 inches spaced apart.
If you have chosen a variety that grows taller than 3 feet, I recommend staking. Otherwise, with the first wind gust your dahlia will fall over.
When your dahlia is about 4 inches tall, I recommend pinching and removing the inner stem. This will force side shoots, and you'll have a bushier plant. You'll start to see your first buds form in July.
Enjoy your dahlias for the summer, and after the first hard frost hits, your dahlia plants will turn black and die off. At this point, you'll have to dig up the tubers, and store them at approximately 3-5 degrees C until spring, when you'll be ready to do plant them all over again!