Dahlia Reach Flowering Peak in Fall

Dahlias are spectacular plants with large, showy full double flowers often 8 or more inches in diameter. Plants producing these flowers are often 6 to 7 feet tall. Not all dahlias are such giants, however, and many of the bedding types produce small flowers on plants only 1 to 2 feet tall. These are used for color masses rather than for the beauty of individual flowers.

Early Spanish explorers found the ancestors of the garden dahlia in Mexico and took seeds back to Spain. Even today, wild dahlias can be seen flowering during the months of August and September in the Highlands of Mexico. However, the development of the garden dahlia as we know it took place in Europe. Although small bedding dahlias have become popular, the tall, large-flowered types have been planted less frequently in recent years except among dahlia fanciers. Most likely this is because the tall-growing plants are more difficult to use in small gardens and staking is necessary. Dahlias are not frost tolerant, and in our climate their roots must be dug and stored each fall.

The large flowered types, which are often fairly expensive, must be saved. The small bedding types are grown from seeds, and although they also produce a fleshy root which could be saved, this is not normally done. New seeds are sown each year because these small plants flower quite quickly even though plants are still small. If the dahlias you are growing have not lived up to expectations, determine how well you have fulfilled their cultural needs.

Dahlias need full sun for at least 6 hours a day, preferably longer. Soil for dahlias should be fairly rich. Well rotted manure dug into the soil a few weeks before planting in the spring will be very beneficial. If none is available, add other organic matter to the soil and supplement it with a garden fertilizer. Dahlias are heavy feeders and require high fertility. Use about ¼ pound of garden fertilizer such as 12-12-12 to each 10 square feet of garden space. Time released garden fertilizers are especially good because they give constant uniform feeding that dahlias need.

If these slowly available fertilizers are not used, a repeat fertilization should be given in July. Dahlias need a lot of water, and should be watered regularly as weather becomes hot and dry. In wet weather or where planted too close together, dahlias are subject to a disease called powdery mildew. Although it usually does not become a problem until late summer, fungicide sprays may be necessary to control it when it develops.

Insect pests may attack dahlias at this time of year. Stalk borers may already have done their damage. These peats enter stems in late spring and tunnel through the stems during the summer. They may not kill a plant, but weaken stems so they break off. If they have been a problem, sprays next season during late May and throughout June should help control them. Cucumber beetles and thrips may be attracted to the dahlia flowers. Grasshoppers will damage both flowers and leaves. Mites, leafhoppers and aphids may also make appearances. Always treat promptly with an insecticide as these pests are noticed.

Dahlia roots should be dug in the tall after the first light frost has damaged the tops. Dig roots carefully and let them dry a few hours before storage. They should be kept at 35 to 40 degrees and kept moist enough so they will not dry up, but dry enough so they will not rot. Pack them in boxes of peat moss or sawdust. Loose plastic bags also provide good protection. Check them monthly during the winter as any problem can be promptly corrected.

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