Large dahlias can grow from 3–4 feet (1–1. 2 meters) tall. Medium dahlias (also known as border dahlias) will reach between 1–2 feet (0. 3–0. 6 meters) in height. Small dahlias will only reach between 10–20 inches (25–50 cm) in height.
If you live in a remote location and do not have access to a nearby plant nursery, you can purchase the dahlia tubers online instead. Check the websites for major online plant retailers including Eden Brothers, Dahlia Barn, Dahlias. com, or Harris Seeds.
Dahlias don’t do well in long, hot summers, so if you live in zone 10, you may need to cover outdoor dahlias or bring them indoors in summer. [3] X Research source If you live in zone 7, dahlias may be able to survive an outdoor winter if you insulate the soil over the tubers with a thick layer of dry mulch.
If you plant the dahlias too early (e. g. in March or April) and another frost comes, the tubers will die.
If you’re concerned that the soil may not drain well, add sand to your soil to improve your garden’s drainage. Do this at the same time that you’re adding the compost or manure. If your soil is clay heavy, work peat moss or compost into the soil to loosen it. This can make it easier to plant dahlias.
For smaller varieties, leave 2 feet (0. 61 m) between holes. For medium or giant dahlias, leave 2 to 3 feet (0. 61 to 0. 91 m) between holes. [9] X Research source
You can purchase ground bone meal at a local plant nursery or gardening center. If you do not already own compost and fertilizer, you can purchase them from a large gardening center or from a landscaping outlet.
Wait until you see new growth above the soil before you water the dahlias. It can take anywhere from several days to a couple of weeks for new growth to appear. [12] X Research source
It’s not necessary to water the dahlias every day. Keep an eye on the plants and, when they begin to look a little wilted, water them generously. In general, it is best to water dahlias 2-3 times a week during the hottest part of the summer.
You can purchase low-nitrogen liquid fertilizer at a local garden center or plant nursery. It may even be available at a supermarket. Look for a 5-10-10 or 10-20-20 mixture.
You can use a plain wooden stake or dowel to secure the dahlias. If you’d rather have a more decorative garden, purchase a cylindrical tomato cage and let the dahlia use it as a support.
If you’re not concerned with producing large, impressive flowers (of the type that would be entered in a flower competition), you don’t need to disbud the plant. Simply let the buds grow where they will.
Store your tubers in an area where temperatures will remain between 45° and 55° F (7°-13° C).
