Are dahlias annuals or perennials or what exactly is their bloom like, should you choose to grow these flamboyant bloomers?
Dahlias are a genus of tuberous plants which are members of Asteraceae family. It is a related species of the sunflower, daisy, zinnia, and chrysanthemum. They grow from small tubers that are planted in spring and produce a rainbow of colors that ranges from petite 2-inch lollipop-style pompoms to giant 15-inch dinner plate blooms.
These beautiful bloomers grow up to 4 to 5 feet tall. They thrive in moist, moderate climates and brighten up any garden with their colorful blooms.
Are Dahlias Annuals Or Perennials?
Dahlias are considered to be tender perennials. This means they may be annuals or perennials depending on the hardiness zone they grow in. Dahlias grow as perennials or annuals depending on the climate you are growing them in.
But Can Dahlias Be Grown As Perennials?
Perennials are plants that live for at least 3 years. Tender perennials are not the same as perennials as they do not survive cold winters.
Tender dahlia plants are tropical plants and they are perennial only if they grow in USDA hardiness zone 8 and higher. If your hardiness zone is below 7, you have a choice to either grow them as annuals or dig the tubers and store them until spring when you will replant them again.
In order to get the most out of your dahlias, you will need to determine your zone before growing your flowers.
Follow These Tips To Help You Grow Vibrant Dahlias Each Year
- Zone 10 and Above, you can grow your dahlias as perennials. The plants will not need any winter protection, they will be able to withstand the frost.
- Zones 8 and 9, your plant’s foliage will die back after the first killing frost in autumn. Cut the dead foliage at this point to 2 to 4 inches above the ground. Cover the tubers to protect them from frost with at least 3 to 4 inches of bark chips, straw, pine needles, or any other type of mulch.
- Zones 7 and Below, trim the dahlia plant to a height of about 2 to 4 inches after the frost has come and darkened the foliage. Dig out clumps of tubers with a spade or fork then spread them in a single layer in a shady frost-free location. Allow the tubers to dry and then brush off the loose soil. Store the tubers in a basket or paper bag or cardboard box full of sawdust, vermiculite, or peat moss. Do not store them in a plastic bag or container as they will rot. Place them in a cool dry place where the temperatures are consistently between 40 to 50F. Be sure to check the tubers occasionally throughout the winter months to check if they look shriveled or have begun rotting. Mist them lightly if they begin to look withered. If they show signs of rotting, cut off the damaged area to prevent it from spreading to other tubers.
Be informed that zone 7 is the borderline zone for overwintering dahlias. In case you live in zone 7b, dahlias may survive the winter but must be covered with a very thick layer of mulch. These tubers are very fragile so treat them with care when handling them.
When warm weather arrives, you can plant the overwintered tubers again and let the cycle start again.
How To Re-Grow Dahlias After The Frost
- Once the threat of frost has passed, plant your tubers in warm regular garden soil. Plant them in a location that gets at least 8 hours of direct sun per day.
- Dahlias may grow tall, stake the ones that grow taller than 3 feet using cages, rods, or bamboo sticks.
- Water deeply at least 3 times a week depending on your type of soil. Do not under or overwater as this will kill them. Dahlias love plenty of water during their growing season.
- Provide enough nutrients but avoid high nitrogen fertilizers. Choose a fertilizer where the first number is half of the other two. This means the nitrogen level is lower than the other nutrients. Apply the fertilizer once a month.
- Remember to pinch or cut the center shoot just above the third set of leaves when the dahlias reach a height of 18 to 20 inches tall.
Dahlias make some of the best bouquets and flower arrangements. Harvest your blooms before they open fully in the cool of the morning or any time of the day. Some people recommend placing the stems in very hot water of about 160 to 180 degrees in a metal container and let the stems and water cool together for an hour.
This sets your blooms and makes your flowers last at least 4 to 6 days. To promote longevity, change the water in the vase daily and use a flower preservative. Even if you are not harvesting dahlias for bouquets, it is best to snip the flowers to allow this plant to produce more flowers and a fuller plant. To promote re-blooming, remove any browning flower heads.