Dahlias don't need any special care to put on a great show in your garden, but there are two easy techniques that will give you even better results.
Pinching or "topping" young dahlias will give you stronger, bushier plants with more flowers. This holds true for all types of dahlias, whether you are growing border dahlias, decoratives or dinnerplates.
When to Do It. The best time to pinch is when the plant is between 12" and 16" tall and has at least 4 sets of leaves on the center stalk. At this stage, it is growing rapidly and will quickly recover from being pinched.
How to Do It. Locate the upper-most sprout on the main stem and snip it off with your fingers or scissors. Take care not to tear the stem or damage the nearby leaves. See the image at above.
Why Do It. Removing the plant's terminal bud will stimulate lateral buds (lower on the stem) to develop into new stems. Where the sprout was removed, the plant will generate two shoots rather than one.Pinching temporarily redirects the plant's energy toward producing stems and leaves rather than buds. It will take an extra week or two to get flowers, but it's definitely worth the wait. Your plants will be stronger, fuller and easier to manage. Plus, all those additional growth points will give you many more flowers. A benefit you'll still be enjoying in October.During the summer and early fall, when your plants are in full bloom, cutting flowers for bouquets has the same beneficial effect as pinching. It keeps the plants bushy and stimulates more bud production. Removing spent flowers -- or deadheading -- does the same thing and also helps the plants look their best.
STAKING OR CAGING DAHLIAS
There's no need to stake border dahlias and other types that are under 2 feet tall. Full-size dahlias, and especially those with large flowers such as dinnerplates, perform better when their branches and blossoms are supported. If you're growing dahlias in a cool, cloudy climate (or in partial sun), the plants will get taller than they would in a hot, full sun location. This makes staking even more important.
The best time to stake or cage dahlias is before or right after you plant them. That way you won't accidentally damage the tubers when inserting the stakes. But even if you don’t get around to it until the plants are several feet tall, it’s still worth doing.
Here are several ways to support your dahlias:
Wood Stakes. For large dahlias, you'll want to use a 1½” or 2” square, 6’ tall hardwood stake. Position the stake about 3" away from the center stem and then pound it into the ground at least 12" deep -- deeper if you garden in sandy soil or are in a windy location. As the stem grows, tie it to the stake, leaving a little slack so the stem can move around in the wind.
Bamboo Poles. This is another popular option. Bamboo poles work well and are easy to handle. For large plants, use 5’ or 6’ poles that are about 1” in diameter and allow 2 or 4 poles per plant. Position the poles on either side of the plant or in a square with the dahlia in the middle. Use string to encircle the plant, wrapping the string securely around the poles. Creating a spiderweb of string that runs through the center of the circle will add more stability.
Metal Rebar. Purchasing rebar and cutting it into 6' lengths is an investment, but your dahlia stakes will last several lifetimes. Rebar is also very easy to pound into the ground, even if your soil is heavy. Use one stake per plant as you would for the wooden ones.
Tomato cages. If you're OK with the aesthetics, this is an easy and effective way to support dahlias. Square tomato cages that fold flat for storage are ideal --, especially for the tall varieties. The round ones work well if you make one modification. Use bolt cutters to cut off the legs and then position the cage so the wide end is resting on the soil surface. This gives the cage a stable base. Use metal ground staples or tent stakes to anchor it securely. Match the height of the cage (3' or 4' tall) to the height of your dahlias.
These small investments at the start of the growing season will ensure you get to enjoy a bumper crop of beautiful blooms.