Do the Dahlia
Learn how to grow and divide spectacular dahlias for long-blooming summer color.
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For long-blooming summer splendor, it's hard to beat the dahlia. Master gardener Paul James and expert Dick Parshall discuss why — when it comes to spectacular performances — dahlias really deliver.
Dahlias have so many different looks. From demure and perkyto defiant and twisted, variety is just the tip of the tuber when it comes to these garden darlings.
"I used to grow iris and tulips in the spring," says Parshall, "but they bloom and then in a week or two they're gone. The dahlia keeps blooming and giving all season long."
So why don't you see more dahlias growing? They can be a bit fussy about the climate — they usually can't take a lot of heat.
In warmer zones, they need a little shade in the afternoon, and in cooler climates, full sun will help. Parshall's 65-degree, Pacific Northwest summer days are perfect for them.
But perhaps the root of the plant's pickiness goes deeper. Dahlias have tuberous roots — fleshy, bulb-like roots that grow underground. Somewhere along the line, dahlias developed a reputation for being tough to grow. But Parshall disagrees. "You don't have to be a trained botanist. [Dahlias] will grow very easily with a few simple techniques that anybody can learn."
The first thing to remember when growing dahlias is that they can grow quite large. Parshall recommends planting dahlias near stakes in a six-inch planting hole that is deep enough to provide freeze protection underground. Plant the tuber with the eye — a little white bump — facing up.
Cover the tuber with a few inches of soil, put a little bone meal or blood meal over the top, and then add a small amount of time-release formula. As the plant grows, continue to fill in the hole to ground level, or even higher if additional support is necessary.