Dazzling Dahlias

By Melanie Mathieson
Gardening Guru

As dahlias are considered one of the most spectacular garden flowers, they can provide the colour and excitement of exotic species that we are unable to plant in our zone. There are thousands of varieties of dahlias that range, from the showy dinner-plate size to the bright, little single ones. The flower shapes and colour combinations are spectacular and some of the flower petal shapes are unbelievable. From pompom to those with needle like petals it is hard to pick a favourite.
Many gardeners shy away from dahlias as they are thought of as a type of flower that requires a great deal of car. This is true to some extent as dahlias are tubers that need to be planted and then dug up and properly stored for winter. But if you think about it, this may be worth the effort, as you can keep the tuber from year to year if properly cared for and beautiful dahlia blooms will grace your garden from July until frost. Although a few of the varieties need extra fussing (read the label to determine) during the growing season, most need the same care as any other annual or perennial.
Some dahlias may provide an abundance of cut flowers, while others will give you the opportunity to make a bold statement in your landscape by pruning, disbudding and ultimately forcing the plant to create a few single, gigantic blooms. Dahlia plants range in height from 12 inches to as tall as 8 feet. The flowers can be as small as 2 inches or up to a foot in diameter. You should therefore consider the ultimate goal of what you want from a dahlia, as well as deciding on the available space when choosing the varieties you wish to grow. Novice dahlia growers may want to start by selecting a few plants of varying colors, sizes and types. Dahlias can also make a statement as the focal plant in a large container. I am considering trying dahlias in containers this year. You have to deal with containers each fall to clean them out and put them away for the winter so tending the dahlias in the fall will require no extra work.
Dahlias should not be planted until all HYPERLINK “http://www.thegardenhelper.com/hardiness.htm” danger of frost has passed and the soil temperature reaches 58-60 degrees F. Excessively wet soil may cause the tubers to rot so wait for the soil to dry out. Make sure the location receives full sun. Dig and prepare a 12 inch diameter by 12 inch deep planting hole. Mix a shovel full of compost and a handful of bone meal into the soil that you removed from the hole. Fill the planting hole with the enriched soil mixture until it is about six inches deep. Place the tuber horizontally in the bottom of the hole with the eye pointing upward. Tall varieties will need staking, so this is a good time to set an appropriate size stake into the ground next to the tuber (near the eye). This will prevent damage which can result if it is added after the tuber has begin to grow. Cover the tuber with about two inches of your soil mixture and water thoroughly. When the sprout begins to emerge from the soil, gradually add more soil mix until the hole is entirely filled. Once the plant attains sufficient height, secure it loosely to the stake. I recommend using a length of an old nylon stocking because it will stretch as the plant grows. Add more ties as the stem grows until the plant is supported approximately 24 inches below the eventual top of the plant. A dahlia in bloom is a heavy feeder, so you may want to consider regularly using a water soluble “bloom type” fertilizer starting about a month before the plants begin to bloom. Read the directions carefully before fertilizing.
Dahlias which have been started in pots may be planted in the prepared hole just like planting any other HYPERLINK “http://www.thegardenhelper.com/plantinghole.html%20” perennial plant. Bedding dahlias can be planted 9 to 12 inches apart. The smaller, flowering types, which are usually about three feet tall, should be spaced two feet apart. The taller, larger-flowered dahlias should be spaced three feet apart. Dahlias tend to have shallow roots so be careful when cultivating. About the end of June, mulch plants with well-aged compost, aged manure, peat, or straw. Water plants regularly if rain is insufficient but avoid wetting the foliage. Do not fertilize dahlias after mid-August.
When the plants reach a height of three to four inches, pinch the terminal bud just above the second pair of leaves. This will produce two main stems. When flower buds are visible, begin removing the buds. This will increase the bloom size of the leader bud and improve the flower stem formation. Flower buds come in three’s. The central leader bud will produce the largest bloom. There will be a smaller flower bud on each side of the leader bud. Remove these side buds by pinching or cutting to the base of the leaf axil. Further down the same stem, two more buds will be found in the leaf axils and which should be removed also.
Major pests of dahlias include aphids and slugs early in the growing season and mites in mid- to late-summer. Leafspot and dahlia wilt also can be problematic. Should the leaves yellow in a random pattern it should be removed from the garden immediately and disposed of in the garbage. Also, destroy plants with abnormal or deformed crowns.
Lift dahlias after the first frost or before the end of October. Because tubers may have spread quite a distance, begin digging far enough from the plant so as not to damage them. For easier lifting make several cuts into the soil with the fork or spade around the clump and gently pry to raise the tubers intact. Once the tubers are out of the soil, remove as much soil as possible without damaging the tubers and leave them to dry. Cut the foliage off so that all that remains is a three to four inch stem on the roots. Soil may also be washed from the tubers with water. Cut off any small roots. Remove and discard tubers that are damaged or diseased and dust any cut surfaces with sulfur. Make sure you label each one carefully before storing. Place the tubers in wooden flats, bushel baskets, or cardboard boxes that have a few inches of peat moss, sawdust, or vermiculite in the bottom. Then cover them with the same packing material, leaving the stems exposed. A little moisture may be added to prevent shriveling. Place the packed tubers in a dry, 40 to 55 degrees F location. Check tubers in a few weeks and again in January for signs of shriveling or fungal infection. Add a small amount of moisture if shriveling has occurred. Do not expect 100 percent survival.
Bring the tubers out of storage in March or April and locate eyes on each tuber. With a sharp knife, divide the tubers with a portion of crown attached, so that each piece has an eye. If eyes are not evident, place the tubers in moist leaf mold, peat, or soilless mix. In a week or two the eyes will appear. Pot the divisions in a sterilized, soilless mix or porous potting soil with the crown above the potting medium. Provide the potted divisions with maximum sunlight and a temperature of about 55 degrees F. Water when the potting mix dries to a depth of one inch. Good ventilation will help prevent disease.
One of the greatest rewards from dahlias is that they make great cut flowers. For the best cut flowers, cut them early in the day, when they are first opened. Immediately place them in water which has set for 24 hours to allow any chlorine to dissipate and change the water daily. Cut dahlias will last from 5-7 days.

Stop at your local nursery supply and buy some dahlia tubers or potted plants and soon you’ll be dazzling friends with your dahlias.