John Spangenberg with his show dahlias in his garden in Damascus. (Adrian Higgins/The Washington Post)

The older I get, the more I like dahlias, perhaps because they keep looking their best until they drop.

A few degrees of frost, when it comes, will blacken their leafy mass, but until then the tall, bushy dahlia offers an in-your-face bouquet of blooms of extravagant form, color and size.

From the plump little tubers of May comes a carnival of blooms in late summer and early fall, when they are most needed.

When you stop to examine, say, a pompon dahlia such as Stoneleigh Joyce, with its gathered petals clustered into a ball the size of a tangerine, it is hard not to fall for this tropical belle. The bloom is held up like a drumstick and has the sort of perfection a hobbyist looks for: the Fibonacci patterns bestowed by a high petal count, and a perfectly spherical shape. Most of all, dahlias have colors that are as saturated and chromatic as they come. Some are sizzling yellows and pinks, others are a more smoldering crimson or butterscotch. Stoneleigh Joyce is an opulent scarlet.

When the dahlia fever grows strong, you end up with a garden like that of John Spangenberg, whose back yard in Damascus is a shrine to the flower. The yard is a series of raised beds separated by lawn and framed by evergreens. From their weed-free mulch of leaf mold, 500 dahlias produce blooms of every stripe, growing through a horizontal mesh of white plastic netting. The most precious and sensitive are shielded against the rain and sun by two dozen or so staked and open umbrellas. The effect is bizarre. “I have to train new neighbors,” he said, laughing.

A Dahlia Bloomquist Sweet. (Adrian Higgins/The Washington Post)

For a long time, I have favored the daisylike, single-flowered types that echo the wild forms because they lend themselves to mixing with other garden flowers. But I have come to love all smaller-flowered dahlias — relatively speaking, perhaps five inches across and less — because of their love of the vase. The pompons and larger ball forms seem made for cutting. I asked Spangenberg to point out some of his favored dahlias for that.

Some are not publicly available, it should be said, because he has raised them himself: He trials 200 seedlings a year; most he deems “junk,” but a handful are beauties. The bees select the parents, but Spangenberg picks the keepers, and through skill and serendipity he has developed varieties that are now passing muster in the garden and on the show bench.

Other favored varieties are available from the catalogues and at spring tuber sales by the National Capital Dahlia Society. Their names are often mind-bending. Camana Mordor is a ball type that reads as red but has a yellow interior. Chimacum Troy is smaller, and a deep and rich purple-red. Hollyhill Rudolph is stout and scarlet.

One of Spangenberg’s home-bred dahlias is a salmon-pink beauty named Crazy George. Nearby grows another long-stemmed ball type with a soft orange glow. He calls it Crazy 4 Martha. In another bed, he shows me Hollyhill Goldrush, which is a five-inch cactus type, dripping with salmon-orange petals and yellow centers. “Good color, orange in the backs of the petals and a huge petal count,” he said.

In a discrete bed between his garage and rear deck, he grows his single-flowered dahlias — this is to minimize the risk of bees pollinating them with the fuller types — and here he points out Bloomquist Sweet, a strong pink collarette with a showy central disc, and the size of a saucer. “It’s a great show flower and a great garden flower,” Spangenberg said.

Because of the sheer number of dahlias, he grows them through the six-inch netting — taut, strung in three layers a foot apart, and perfect for securing stems against a bullying wind. Other growers use tomato cages or individual rebar stakes. The dahlias simply grow through the net; without it, he wouldn’t have time to grow so many, he said.

Another growing tip? Lateral buds erupt from lower-leaf axils. By pinching them out when small, you avoid congested flowering and weaker blooms. This also makes for long, straight stems that you need for cutting. Disbudding “is a big hurdle for people to get over, but it’s so much better of a flower for it.”

November and December are the months serious dahlias fans harvest the tubers. After the frost, Spangenberg uses a lopper to cut off most of the damaged stems. You can leave the tubers in the ground for a couple of weeks to harden off a bit, and then lift them carefully with a garden fork. You will find that your single tuber has multiplied a dozenfold. You can either separate the tubers then or wait until after winter storage, though Spangenberg likes to sever them in the fall when they are easier to cut.

Each one is dusted with cinnamon — it acts as a fungicide — and placed in a sealed plastic bag filled with vermiculite rather than peat moss (too damp).

Stored indoors, most tubers will make it through and be ready for potting up in April. You are then faced with the problem of finding homes for them.

A lot of people who like dahlias are scared off by this digging, cutting and storing regimen. If you’re one of them, he says, simply don’t bother. Treat the $5 dahlia for what it is, a cheap and cheerful annual that rewards a little care with a lot of heart.