How can a flower that is as big as your head not be great?

Dahlias are an extremely varied group. The American Dahlia Society recognizes 18 flower forms, nine flower sizes and 15 color categories. Sizes range from giant (greater than 10 inches) to miniature (less than 4 inches). Flower forms bear such exotic names as "incurve cactus," "mignon single" and "steller."

With the thousands of varieties available, it's highly unlikely that you won't find a few that appeal to you.

Dahlias bloom from midsummer until frost and can be enjoyed in the garden or as cut flowers. Be sure to wait until they are fully opened before cutting.

In Western Pennsylvania's climate, dahlia tubers must be either sacrificed at the end of the season or lifted for overwintering indoors. While the latter may seem daunting, the reality is that overwintering is fairly simple.

Start by tagging or identifying varieties. This can be done with minimal cost and effort by tying color-coded yarn around the base of the plants. Then, cut the foliage down to about 6 inches after the first damaging frost. Carefully dig up the tubers, keeping in mind that they will be larger than when planted at the beginning of the season. Using a pitchfork may prevent some tuber damage.

To dry them, gently remove the soil and place them in a container full of dry sand or vermiculite. Ideally, the tubers should not touch each other.

While that is the textbook way to overwinter dahlias, every grower has his or her own system. Sphagnum peat moss, sawdust, shredded newspaper, perlite and Styrofoam peanuts have all been used to store tubers. Some folks even leave the soil on and simply place them in an open garbage bag. Others place clean tubers spaced apart in open trays.

Whatever your personal process entails, place the (not air-tight) container in a cool, dark location that will not experience sub-freezing temperatures. Check the tubers periodically to make sure they are not rotting. If you find some suspicious soft spots, discard the affected ones.

In the spring, after the danger of frost has passed, unpack them and use a sharp knife to cut the tubers into sections, making sure each section has one to three buds. As the numbers grow, extras can be shared with friends and family.

Dahlia tubers should be planted in full sun, buds pointing up, 4 to 6 inches deep and 2 to 3 feet apart. You may wish to enrich the soil with compost or other organic matter to a depth of 12 inches.

Make sure dahlias receive at least 1 inch of water per week after planting. Place stakes with tubers for larger varieties at the time of planting to prevent impaling them later. Tie the stems to the stakes as needed for support, usually every 8 to 12 inches.

When choosing stakes, keep in mind that the dahlias may get to be more than 5 feet tall with stems 3 inches in diameter. This summer, in Phipps Conservatory's Discovery Garden, we used stakes that are 5 feet long and 1/2- to 3/4-inch thick. They were neither tall enough nor sturdy enough. A 6- to 8-foot length of at least 1-by-1 lumber is recommended. Half-inch steel rebar (primed and painted to prevent rusting) has been used, also.

Last winter, Phipps became the proud home of Frieda's Garden, which honors the memory and support of Phipps by the late Frieda G. Shapira. An avid gardener and Phipps trustee, she was well-known for growing beautiful dahlias.

This summer, Frieda's Garden became a celebrated feature of the bee garden. The huge, bright flowers are the perfect addition to this space enjoyed by children and adults. Many of the collection's heirloom varieties have flowers that are more than 6 inches in diameter on plants as tall as 6 feet.

Included in the current collection are nine varieties, two of which are known to be prize winners. 'Otto's Thrill' is a large, informal, lavender dahlia that was introduced in 1956. 'White Perfection' is a large, formal white dahlia that has been around since 1967.

When the flowers were at their peak this summer, we had cutting afternoons in which our young visitors received a dahlia to take home with them. After the first frost this fall, the dahlia tubers will be lifted from the ground and stored. When life renews itself this spring, we will again plant these unforgettable treasures in Frieda's Garden.