It is important to note that dahlias are grown from tubers and not bulbs. Tubers have "eyes", for example a potato is considered a "tuber." Bulbs, such as tulips, daffodils and lilies, can be planted in the fall when the ground is cold and wet. Dahlias must be planted in the spring, after all danger of frost has past and the soil has warmed. Dahlia tubers should be dug up in the fall, divided and stored over winter and re-planted again in the spring.

Soil Preparation

If you have heavy, clay soil, amend with sand, peat moss, steer manure or compost to lighten and loosen the soil texture. Dahlias prefer a pH level of 6.5 - 7.0.

Be careful not to amend your soil that it is too rich in organic matter. Dahlias originated from the mountains of Mexico and thrive even in average soil that is well drained. Dahlias like well drained soil. A mixture of 50% organic matter and 50% native soil is a good mixture.

Where to Plant

Plant your dahlias in a sunny location that receives at least 6 hours of sun per day.

When to Plant

Plant in the spring after soil has warmed and all danger of frost has passed. Check your almanac for the last frost date in your area. April through May is usually a good time.

Planting

Space your dahlias 18" - 24" apart. Lay the dahlia tuber flat, about 4-6" deep with the eye of the tuber pointing up. Planting time is the best time to install stakes, before the tuber begins to grow. Don't use bark or mulch to cover dahlias at this time, as it doesn't allow the soil to warm up or the tubers to sprout. Do NOT water at time of planting. During normal springtime rainfall, the soil has enough moisture to fulfill the dahlias needs.

Watering

Springtime offers enough rain to fulfill the tubers needs until the sprouts appear above the ground. Dahlias are very susceptible to rot. Too much water will cause the tuber to rot. It's best if the soil is a bit on the dry side, rather than the wet side. Once the dahlia is established, a deep soaking once or twice a week during summer should be sufficient.

Fertilizer

Bone Meal is recommended at planting time. Bone Meal builds strong tubers. Dahlias require low nitrogen fertilizers. We recommend fertilizers with a 5-10-10 ratio within 30 days of planting and again approximately 4 weeks later. Do Not overfeed your dahlias, doing so will promote weak stems, small blooms or tubers that rot or shrivel in storage.

Weed Control

Hand weeding is the only type of weed control you should use. Never use any type of herbicides around your dahlias.

Pests & Problems

Slugs love dahlias, especially as they are emerging from the soil. Use the slug bait of your choice until your dahlias are at least 12" tall. After the dahlia has reached full height, no slug bait is necessary.

Earwigs can also be a dahlia pest. Earwigs can be controlled by spraying an insecticidal soap on your dahlias every two weeks during the growing season. Any over-the-counter product will do or take a standard spray bottle, add two tablespoons of dishwashing soap and fill with water. Spray as needed.

Diseases

Dahlias can be susceptible to powdery mildew and other types of fungus. Keeping the leaves dry as possible will help to control fungus. Fungus thrives in wet conditions. At the first sign of any fungus, spraying with any type of fungicide every 10 days, until the fungus is under control. Preventative sprays can begin in June to control fungus from starting and spreading in late summer.

Pinching your Dahlias

To promote a compact, bushy plant with more blooms, pinch out the center growing tip right above the 3rd full sets of leaves, when the dahlia is 12" - 18" in height.

Cut Flowers

To ensure continuous blooming from August until frost, remove all dead blossoms. Cut flowers in the morning or at dusk. If the water is changed daily and the stems are re-cut, the dahlias will last for a week.

Digging Dahlias

It's important to wait for a frost in fall before digging your dahlias. Wait at least one week after a frost before digging your dahlias. During this time, the dahlia is 'ripening' and preparing itself for winter. Dahlias dug too early will not store over winter. If you live in an area that does not freeze, withhold water from your dahlias in fall to force them into dormancy in the fall. Cut down the dahlias stems to a height of 6"-8" and use a pitchfork to gently loosen the soil around the dahlia and lift the dahlias out of the soil.

Do I really need to dig up my dahlias?

Digging and dividing will keep your dahlias returning year after year when they are dug and stored properly. Dahlias left in the ground will create a massive tuber clump underground that will send up many weak, unproductive stalks that have small blooms. Eventually, if left undug year after year, they won't come back at all. You can treat your dahlias as annuals and purchase new tuber stock each year.

If you live in an area that does not have harsh, freezing winters, your dahlias may survive winter without digging. In the fall, wait at least 1 week after a freeze and after your dahlia stalks have died back completely. Then cut the stalks down to the ground and place a 10"-12" layer of mulch such as grass clippings, leaves, straw or compost. This will protect your dahlias over winter. In March, remove the layer of mulch so that the soil can begin to warm up. Dig up the tubers, divide and replant them right then.

Although, we do recommend digging, dividing and storing in the fall, you should have success with this method as well.

Dividing Dahlias

Rinse all the soil off the dahlia clump. When dividing dahlias, the first thing to do is to remove all broken tubers, remove the original 'mother' tuber and remove any tubers that are rotten. You can divide now or keep the cleaned-up clump in tact and divide in the spring. In the spring, the eyes are easier to see. It's very important to get a piece of the swollen part that is attached to last years' stem. The eyes will emerge from the swollen part of the dahlia that is attached to last years' stem. If your tuber does not have an eye, it will not sprout. Choose only strong, firm tubers. Weak tubers that show signs of rot, shriveling or decay should be tossed and not used in the garden.

Cut surfaces should be allowed to dry thoroughly before they are planted in the garden or stored for the winter. Lay out to dry for 3-5 days in a place that will not freeze, then store for the winter.

Our step by step tutorial of the tuber dividing process:

For a printable copy (PDF)

Fungus

If you had any problems with fungus on your dahlias in the summer, soaking them in a mild bleach solution will kill any overwintering fungus. After cleaning up the tuber clump or dividing your tubers, soak them in a mixture of 2 cups household bleach to 1 gallon of water for 15 minutes. After soaking, rinse tubers thoroughly with clean water. Let dry for 3-5 days in an environment that is above freezing, then store for winter.

Easy Dahlia Storage - Warmer Winter Climates

Follow the directions for digging and dividing dahlias. After the tubers or tuber clumps have dried for 3-5 days, place the clumps in a paper grocery bag and put them in an environment that is above freezing and stays at a temperature of 40-50 degrees. An unheated garage will typically be the best storage place as long as it never freezes in the winter. Check the tubers monthly during winter and mist with water if they appear to be shriveling or drying. This can be an easier way to store your dahlias if you live in a climate that does not have harsh winters, such as the south and parts of the northwest. In the spring after all danger off frost has passed, bring out your dahlias, divide if you didn't divide before you stored them, and plant !!

Winter Storage - Colder Winter Climates

A week after a hard frost, cut down the dahlia stems to a height of 6"-8" and lift the tubers carefully with a pitchfork. Rinse all soil off the dahlia clump, remove the remainder of the stem, remove any broken tubers, the original 'mother' tuber and any weak or rotten tubers. Divide the dahlias now or store in clump form. Let dry in an area above freezing for 3-5 days. The tubers must be very dry before going in to storage. Store in a cardboard box, a wood box or a plastic box or tub. Bury the dahlias in a medium such as 50% slightly dampened peat moss and 50% wood shavings (or pine shavings purchased at any hardware or garden store.) Peat moss will generally come out of the bail moist and will not need any moisture added to it. The peat moss should be moistened to the point that if you take a handful of peat, squeeze it, no water drips out. Tubers will keep best if the storage area is cool and dark, such as an unheated garage, and always kept above freezing. Too cold and they will freeze and rot, too warm and they will shrivel. Check the tubers monthly during the winter months and mist with water if the tubers appear to be drying or shriveling. Plant in the spring after all danger of frost has passed.

Dahlias do require a fair amount of care and maintenance throughout the year, probably more than the average garden plant. But for all your work, you will be rewarded with armloads of fresh cut flowers during late summer when most other garden plants have finished their bloom. Cut the flowers and enjoy their blooms. The more you cut them, the more they will bloom.

In our opinion, there is no better cut flower than a dahlia and nothing more stunning than a patch of blooming dahlias in August and September. This is why we chose to grow this spectacular flower.

Please contact us at info@dahliabarn.com. We would be happy to answer any dahlia questions you may have.