Gardens

How to Prune a Dahlia

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Dahlias are perennial plants native to Central America and Columbia. They grow from bulbs which germinate in the spring producing flower blooms which last through to the fall. The flowers are used for medicinal purposes and decoration. There are over 35 species of dahlia, with additional varieties from hybrids. Flower sizes can range from small to dinner plate size, in all different colors and shapes. Dahlias are planted from tubers which are kept indoors over the winter. They are sensitive plants which will die if subjected to frost.

Step 1 - Planting the dahlias

Once the dahlia tubers have been planted, branches will begin to grow with leaves. Once two or three sets of leaves appear, the branches can be pruned. Once the shoot is about 6 inches high, it can be pruned. The branches can be pinched by the thumb and finger. Prune enough branches to get the desired number of stems for flowering. Higher branches will need to be supported once flowering begins.

Step 2 - Remove excess buds

  • The number of flowers will depend on the number of buds. Budding will begin soon after the stems get to a certain height. There may be more buds than necessary so removing the buds or 'disbudding' can begin. If the number and size of the flowers do not matter, then disbudding will not be necessary.
  • Disbudding will increase the flower size of the leader bud. There are three buds in a set. The middle bud will produce the biggest bloom. Smaller buds are on each side of the leader bud. These can be removed by pinching or cutting them to the base of the leaf where it attaches to the stem or 'axil'. To maintain a fuller plant with room for the flowers to bloom and capture the most sun, start the disbudding process at the central stalk, and repeat for all the surrounding stalks. Extra stalks can be removed if there are too many to support the number of flowers.

Step 3 - Prune buds

Pinching or pruning lower lateral buds from the stalks will yield bigger flowers. Higher stalks may require tying to stakes so that they will grow without drooping or breaking off. Keep the plant balanced when leaving buds to grow into flowers.

Step 4 - Prune leaves for pest control

Aphids and slugs are a pest of the dahlia early in the season. Spider mites start to infest dahlias in the mid to late summer, which is the prime flowering time. Prune bottom leaves and use directed water streams to wash off the mites and other pests. Pinch off any small stubs under the bottom leaves, which can become branches.

Step 5 - Prune off faded flowers

After the dahlia flowers, prune the spent blossoms. This is called 'deadheading' and will encourage the plant to produce more flowers. If the stem has buds, it can be pruned down to the bud level to allow the flower to bloom without the stem in its way.

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