Summer Care of Dahlias

They can be the most spectacular of fall flowers, so a little attention now can result in more future pleasure. Although dahlias are native to Mexico, it was in Spain that the dahlia was improved and finally spread throughout Europe where it is still popular. There have been more than 14,000 varieties of dahlia named since the first cultivars were brought into Spanish gardens in 1791.

Since dahlias produce spectacular flowers, they are often considered only show flowers and not garden flowers. However, more recently, dwarf-growing bushy types have been introduced that are suitable for mass garden planting. Some are seed grown, but produce small bushy plants of many different flower forms and colors. Others are named varieties grown from tuberous roots. Whatever class of dahlias is being grown, all need adequate summer fertility. Fertilizer or manure should have been mixed into the soil at planting time. Whether or not this was done, July is time for another fertilizer application. Fertilizers such a 5-10-5 or 12-12-12 may be used at a rate of about ¼ pound per 10 square feel of soil area, or about one square yard.

Scatter the fertilizer around the plants, not too close, and do not get any of it on the foliage. Then, using a hoe, break the soil surface and mix the fertilizer with the soil. Deep cultivation is not necessary. After the fertilizer has been added, a mulch over the area will help maintain more uniform soil moisture. Since dahlias require plenty of moisture, mulch is important when watering can not be done. If possible during dry periods, dahlias should be watered enough to penetrate the soil six to eight inches.

Gardeners growing dahlias for their own pleasure need do little to change plant growth or bud formation. When grown for show, plants should be allowed to develop only one stalk and when flower buds appear the side buds on the main cluster should be removed leaving only a single bud. It takes about 30 days from the time a flower bud appears until it has opened. Dahlias have few pests. Stalk borers and the European corn borer sometimes damage dahlias. The stalk borer is more common in early summer and the corn borer more common in late summer. Both will enter the stems and live in the pithy tissue, weakening and sometimes killing shoots.

Cutting out and destroying damaged portions along with nearby weeds that harbor these pests can be helpful. Garden insecticides may be used to help prevent entry, although they are effective once the pest is within the stem. At times spotted cucumber beetles can damage flower petals and may require spray treatment. Dahlia roots are not normally able to survive our winters if left outdoors and therefore are dug in the fall. Just prior to frost the main stem is cut off and the roots dug and allowed to dry. The soil is then knocked off.

Roots should be stored cool and dry at about 35 to 40 degrees. In storage, dahlia roots must be protected from drying, but not so moist that they begin to rot. Some growers store them in polyethylene bags, or in boxes of lightly moist vermiculite or peat moss. Whatever storage methods are used, dahlias should be checked monthly during the winter to make sure that they are not beginning to rot, or so dry they are beginning to shrivel and decline.

http://en.wikipedia.org/wiki/Dahlia