Learn how to pinch out dahlias for more blooms! Follow these simple steps for stronger stems and double the flowers.
Nothing stops people in their tracks quite like dahlias. They come in a wide range of shapes and colors (except blue) and start blooming when the rest of the garden is fading. A single tuber can produce dozens of huge blooms in late summer and early fall until a frost hits.
The Pacific Northwest has the perfect climate for dahlias, and this year, I'm growing over 50 different ones in a series of raised beds along the sidewalk. I even started growing dahlias from seed to try my hand at producing a brand new variety!
Some dahlia blooms get HUGE! This dinnerplate dahlia, called Otto's Thrill, literally grows to the size of a dinner plate. These giant flowers get really heavy, and the stems can flop over and ruin your display.
But here's a secret – these showy blooms can become even more impressive AND more stable with one simple technique. Pinching dahlias is a tried-and-true method that encourages an abundance of flowers and creates a sturdy base for your stems.
So if you want a flourish of blooms at the end of your gardening season, you need to start your dahlias off right. Here's how to pinch dahlias now for more blooms later!
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Why pinch dahlias?
Dahlias are a "cut and come again" type of plant. That means the more flowers you cut, the more it will bloom!
A dahlia plant has one goal in mind: produce seeds. Each time you harvest a flower, either for an arrangement or deadheading spent blooms, the plant failed to make seeds. It will send out more shoots to try again, resulting in more flowers!
If you pinch a dahlia plant early in its growth, it will produce two shoots on either side of the cut. This is similar to pinching snapdragons and sweet peas, and results in a stronger, more balanced base stem. Each stem will produce the same number of blooms as the original, giving you twice as many flowers!
If you don't pinch, you'll end up with one thick stem with fewer blooms. Once you cut those flowers, the side shoots will be high on the plant, making it top-heavy. The new shoots are also typically more spindly and unable to support the weight of the new flowers.
Pinch early for a bushier plant
I presprout my dahlias about a month before I plan to plant them outside. This process ensures that the tubers aren't dead and that there's a viable eye on each one after dividing.
Presprouting also gives the plant a head start, so it can produce flowers sooner. Pinching will set back the bloom time by a few weeks, so presprouting offsets this delay.
All I do is fill a quart sized ziplock bag with potting soil, then place the tuber inside. Add a spritz of water and keep the bag under grow lights as it sprouts.
Some dahlias take forever to sprout, while others are raring to go! Once the leaves grow past the top of the bag, I move the plant into a larger pot and start hardening them off outside. The slowest growers stay in their bags until they can be safely planted in the ground.
Before the plants go out into the garden, I give each one a little haircut. If you don't presprout your tubers, you can also pinch your dahlias after they're already in the ground.
When to pinch dahlias
It's best to pinch your dahlias when they have at least 3 to 4 sets of leaves and is at least a foot tall. This typically happens about a month after planting, but this can vary depending on your specific growing conditions. Pinching too early could stress young plants, while waiting too long might limit its effectiveness.
If your dahlia is over two feet tall and has more than seven sets of leaves, it's too late to pinch it back. The stem becomes hollow as it gets bigger, and pinching it at this late stage can invite insects inside. Water can also enter the hollow stem and cause the tuber to rot.
How to pinch dahlias
While it can be a little nerve-wracking to cut off all that new growth, it's worth it! Here's how to do it!
Count the leaf sets
Starting from the bottom, count up each pair of leaves on the main stem. You can pinch anywhere above the third set of leaves.
Pinch or cut at the growth point
Grasp the part of the stem with the newest leaves between your thumb and forefinger and bend it over until it snaps. You can also use shears to cut it off, but be careful not to damage the leaves on either side.
Check the stem
If your plant was on the taller side, check the remaining stem after pinching to make sure it's solid all the way through. This area will callous over in a day or two.
If the stem is hollow like a straw, move down to the next set of leaves and pinch again. The new growth that I just pinched off was hollow, so this was the highest point I could pinch without causing issues.
It's better to delay blooms due to a deeper pinch rather than kill the plant entirely by leaving a hollow stem exposed!
Let the cut heal
Be careful not to get water or debris on the pinched stem until it forms a callous over the surface. After a week or two, you should start to see new growth forming on either side of the pinch!
With this simple technique, your dahlias can grow into a fuller, more balanced, and healthier version of themselves, full of vibrant blooms. Once your plant starts to set buds, consider disbudding your dahlias to encourage larger flowers and stronger stems!