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From Mignon to Dinnerplates, Dahlia's Bloom All Summer

By Jos Van Hage

A very popular summer flower is the Dahlia. It originates from Mexico and was brought into Western Europe more than 200 years ago and now through hybriding there are hundreds of different varieties available worldwide. There are so many different varieties that they have been loosely organized into different divisions based on the flower shape and petal pattern as well as size of bloom and height of plant.

A favorite division is the ‘Decorative’ which contains those large ‘Dinnerplate’ varieties with huge sized flowers and are tall growing to make them beautiful for backgrounds. These are showstoppers but usually require a little extra attention as they need to be staked to support the heavy flower or planted in a sheltered area away from strong winds. Other tall divisions are the ‘Fubuki’ which is a new group that produces large decorative-type flowers that are fully double, flat florets with fringed petals. The ‘Cactus’ and ‘Semi-Cactus’ have double flowers and pointed ends that turn inward. ‘Ball’ varieties have fully double flowers that are ball shaped and ‘Pompom’ which is similar to the Ball types except flowers are smaller in size and petals are curved. ‘Collarette’ dahlias have a single outer row of flat florets and an inner row of small florets that form a disc. ‘Water Lily’ and ‘Peony’ types are also both tall.

Mid-height divisions that grow 15-25 inches are the ‘Single-flowering’ which have a single row of florets.’The anemones’ have one or more rows of florets that surround a dense group of tubular florets and ‘Mignon’ have small single flowers.

Shorter varieties are very popular because they make excellent container plant which is great for our climate which has a short growing season. This is because they are easier to protect from the frost as they can be moved to a protected area. The ‘Impression’ types are a new division which grows 12-22 inches in height and the flowers have an outer ring of flat florets and an inner ring of florets that forms a central disc. These also make nice bedding plants along with another new division also great for containers ‘Gallery’ which grows only 12-14 inches tall. They bloom for a long period of time and flowers are similar to those of the ‘Cactus’ and ‘Decorative’ types. ‘Topmix’ has small flowers and is also a small plant.

Dahlias can be grown from seed, but are most commonly grown from tubers. Tubers are available in the garden centers now and should be planted now in order to get a head start on the season so that they will be blooming for the summer. Dahlias are very touchy for frost so you do not want to plant them outside after all threats of frost has passed. To plant use a pot that easily fits the tuber then holding the tuber right side up in the pot fill the pot with good-quality soil leaving the top of the tuber even with the soil surface. Give it a good soaking of water, then place it in a warm sunny location such as a south-facing windowsill. Do not over water the tuber only giving it water when the soil becomes slightly dry so that they tuber does not rot. 

When you start to see growth, you should begin fertilizing the tuber with a plant start fertilizer such as 10-52-10 and then later when the plant becomes larger switch the fertilizer to an all-purpose 20-20-20. To create a busy full plant pinch out the center of each stem once it has three leaves as this causes the stem to form side shoots. Toward the beginning of May you want to harden off the plant by placing it outside during the day and bringing it back in again at night. This will get the plant ready go outside without much stress when the time is ready after all frost has passed.

When transplanting or moving the container outside in late May choose a sunny spot away from extreme hot midday heat. Keep the plant evenly watered and fertilize weekly with 12-36-12 fertilizer which promotes blooms. Also remove any finished blooms before they set seed as this takes away important energy away from the plant that could be used in the making of more blooms. 

The nice thing about dahlias is that the tuber can be dug up in the fall after the first killing frost cutting back the blackened foliage to within 6 inches from the tuber and stored over the winter in a cool (5-8 Celsius) dry place. Make sure that any excess soil has been shaken off the tuber and that it has been air dried in the sun for a few hours in the sun before storing. If you have more than one variety remember to label each tuber with name, color and height. 

Next year in late winter, early spring the tubers are taken out of storage and can be divided into more tubers making sure that there is at least one eye per tuber. Allow the tubers to be in a warm location for a couple of weeks before re-planting them as you did the first time.

-Jos 

Jos Van Hage owns three Art Knapp Garden Centres in the Prince George area
-Highway 97 North
-Highway 16 West
-Highway 97 south at the old Cariboo Highway


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