Dahlias 101: Beginner's Growing Guide
In this beginner’s guide to dahlias, learn how to properly plant dahlia tubers and care for them so you have dahlias blooming all season!
Dahlia is a genus of bushy, tuberous, herbaceous perennial plants native to Mexico and Central America. It’s garden relatives include the sunflower, daisy, chrysanthemum, and zinnia. Dahlias grow from tubers planted in the Spring, and bloom all the way to the Autumn season. Picking a favorite type of dahlia is nearly impossible, as they come in a million different colors! Dahlia flowers range in size from little 2 inch “pompoms” to ginormous 15 inch “dinner plat” blooms, which happen to be my favorite! Most varieties will grow to be 4 to 5 feet tall, so you’ll want to stake them for sturdiness.
The best part about them, aside from their gorgeousness, is they’re perennial! This means they’ll come back every year. Another awesome thing – they MULTIPLY each year! Heck Ya! They’re considered tender perennials in colder regions of North America. The only regions they’re winter hardy in are zones 8 to 11. Gardeners in zone 2 to 7 should plant their tubers in the Spring, and then dig them up and store them during the Winter season. If you don’t know your planting zone, click here. Let’s get started!
Location
Dahlias prefer full sun conditions as they require direct sunlight for a minimum of 6 to 8 hours to bloom. Stiff wind can cause heavy damage to your plants and flowers, so plant them in a place protected from wind. You can also stake them to help prevent damage, which will be discussed later.
Soil
Dahlia plants require well-drained, fertile soil. If soil drainage is poor in your area, add compost or sand to the soil before planting. If the soil is heavy, add compost or peat moss to the soil to loosen it. I have been completely successful growing dahlias by just using regular ole bagged potting mix, so don’t get too stressed on the soil!
Planting
Dahlia tubers can be planted after your last frost date when the soil warms up. April to Mid-May is the best time to plant them in most zones. If you live in colder climates, you can start your tubers in a pot indoors 2-4 weeks prior to your last frost date. Transplant after danger of frost has passed.
Before planting your tuber, work your soil 6-12 inches deep.
Plant your tuber 4-6 inches deep with the “eye” facing up (see pictures below), and 1-3 feet apart depending on the type. (Dinnerplate dahlias will need a little more space). The more space, the more room to flower. If you’re planting in a pot, use atleast a 12″x12″ pot with a stake. It’s best to use clay, heavy pots instead of plastic as the flowers can be heavy!
It’s very important to start with a tuber that has an “eye” or growth bud on the crown of the stem. Tubers without an eye won’t grow a plant. You can purchase single tubers with an eye, or a clump of tubers around a stem. Either one will grow a healthy plant! If you’re having trouble finding the eye, put the tuber in a shallow container covered in slightly damp soil for a few days to encourage a sprout to appear.
After you plant your tuber, cover with soil and avoid heavy watering as it promotes tuber rot. Start watering after the germination of the plant.
Watering
As mentioned above, start watering AFTER the germination of the plant. If you water directly after planting the tuber it can promote tuber rot. Dahlias require regular watering once they have developed. The plant should be given deep watering 2 to 3 times a week. Increase the amount of water during hot and dry seasons. Lack of water can affect the production of flowers. If you’re planting in a pot, you may need to water a little more than in ground planting.
Staking
For dahlias that grow 4 feet or taller you’ll want to put a stake in place to help them stand up. You can use wood stakes or metal rebar that are around 6 feet tall. Plant the stake 3 inches from the center stem and pound it 12 inches into the ground. As the stem grows, tie it to the stake leaving a little slack.
Fertilizer
Start fertilizing 3 to 4 weeks after germination. Fertilize once a month with organic or water-soluble flower fertilizer. Do not use high-nitrogen fertilizer, as stems and leaves will grow but the flowers will get smaller. I have been successful not fertilizing at all, so this is completely up to you and your thoughts about fertilizing!
Trim & Cut
Dahlias grow quickly in the summer. Once the dahlias are around 18” tall, pinch them back by snipping the center stalk down a few inches right above a set of leaves. This encourages more branching, which leads to more blooms later in the season.
When the blooms are fully open, cut them early in the morning or late in the evening. Put them in clean, warm water, and enjoy their beauty!
Storing
Dahlias will bloom until the first frost. Once the first frost hits, they will turn black and that’s the end of their season! Tubers do not like when the soil freezes, so sometimes they will not survive if they stay in the ground! They are typically hardy in zones 8-11, but are more sensitive in zones 2-7.
At the end of November is a good time to cut them back. You’ll lift them out of the ground (I use a shovel), brush off excess dirt and let them dry for a few days. Then, pack your tubers in a plastic bag of peat moss and store them in a cool, dark place. I store mine in my garage. Check on them occasionally for any rotting or mold, and replant in the Spring!
I hope this simple guide helps you out a little in your dahlia planting endeavor! Dahlia’s are such a delight, and there are SO many different types and colors you can get. So, be warned, if you start, you WILL get addited! Happy Planting!
