My blog site is primarily dedicated to growing tropical and subtropical plants, whether as a houseplant or in the garden

Growing Dahlias

Growing Dahlias

My summer garden is not complete without dahlias.  A lot of dahlias.  In fact, I would never have a garden without a few dahlias.  Or maybe 19 dahlias…I planted 19 of them today in my Ohio garden in late April!  This blog post is a guide on how to grow dahlias.  Dahlias make a bold statement in any garden, and I absolutely love dahlias for several reasons:

  • They provide a constant source of blooms all the way to the first killing frost.  Yes, they may start blooming a little later than some plants, but once they start, watch out!  Sure, I grow many perennials in my Ohio garden and I love them, but I intermix many different tropical plants into my garden, and dahlias are among my favorites.
  • After everyone else’s gardens have fizzled out past their prime, mine is just getting started!  Dahlias bloom when many other plants have pooped out.  That’s the beauty of tropicals.  They keep getting better and better as the season progresses!
  • Their bombastic blooms offer a tropical punch to your garden and make a bold statement.  And there are so many shapes, sizes and forms in the flowers.  Dahlias are not for the dainty gardener.
  • Dahlias offer an endless supply of cut flowers.  I’m constantly cutting dahlias to display indoors throughout the season.  One of my favorite things to do, although it’s somewhat depressing, is to cut an armful of dahlias right before the first killing frost, just like in the picture below from my garden a couple years ago.

In late April, I planted my dahlias that I had overwintered in our heated garage.  Any cool, dark place will do.  A cool basement is also perfect.  In the fall, I dig up the dahlias, shake any soil off the tubers, and then let them air dry for a day or two.   Then I store them in either perlite or vermiculite in a box or a pot, and put them away on a shelf for the winter.  It’s as simple as that.

How to Plant Dahlias

Planting dahlias is a piece of cake.  Be sure to locate your plants in plenty of sun.  Dahlias come in a huge variety of heights from just a few inches tall, to towering giants that are several feet tall (and every height in between).  I like to plant the tall ones because I like to  create a living wall in my garden.  My intent was to create a garden “room”  that you could walk into and feel like you are standing in an outdoor room, surrounded my plants.   Since I like to plant the tall varieties, the first thing I do is drive a wooden stake into the ground (I like using 6 foot stakes), and then dig a hole and drop the tuber in the hole. The reason you want to place your stakes in the ground at the time of planting, is so you don’t accidentally drive a stake through your tubers later.   Plant your tubers about 6 inches deep or so and then cover with soil. Dahlias like a fertile, well drained soil.  If you have clay, then you should amend the soil with compost or peat moss in order to make your soil more friable.

Normally, the rain that occurs in our Spring is enough to carry the tubers through until they start sprouting above the soil line.  If your soil is very dry at the time of planting, so ahead and do an initial watering, but go light on the water until they sprout.  Your dahlias are not actively growing yet and you don’t want to cause them to rot.  Once they start growing vigorously, they LOVE lots of water.  Lots of sun and lots of water, but be sure your site has well drained soil.

If at any time there is a threat of frost, be sure to cover the dahlia overnight to protect it.

Fertilizing Dahlias

Dahlias grow quickly enough even without fertilizer, but you still need to fertilize your dahlias for optimal flowering.  Choose a fertilizer that is low in Nitrogen and higher in Phosphorus and Potassium, such as a 5-10-10 fertilizer which is a typical vegetable or tomato fertilizer.  Plants don’t know the difference as far as what the label says!   I’ve made the mistake in the past of using Miracle-Gro on dahlias, but this provides too much Nitrogen and results in gigantic plants with weaker stems and fewer flowers.  Don’t get me wrong, I use Miracle-Gro on plenty of my potted annuals, but it’s not suitable for everything.  It may also cause tubers to shrivel in storage and not make it through the winter.  When you look at a fertilizer, you will see 3 numbers and these represent the “NPK” numbers.  If you remember the periodic table of elements in chemistry class, N stands for Nitrogen, P stands for Phosphorus and K stands for Potassium (I didn’t even have to look that up.  My major in school was chemical engineering). Nitrogen is important for foliage growth.  Phosporus is important for flowering and root growth. Potassium is important for overall plant health and disease resistance.  I’d recommend a 5-10-10 fertilizer for dahlias and apply monthly.  Be consistent with watering and fertilizing, and you will be amply rewarded.

General Dahlia Care

  • Besides the fertilization tips I shared above, be sure to give your dahlias plenty of water.   I can’t emphasize enough that your dahlias should receive plenty of of water and also be on a regular fertilization schedule.  This will ensure a healthy plant with plenty of blooms.
  • If you grow the tall dahlias like I do and have to stake the plant, you’ll have to use garden twine to support the plant as it grows.  Don’t tie the plant too tightly.  Just enough to support it.  You can use other methods of support if you’d like, such as a tomato cage but it might be more difficult to perform any care.
  • One very important tip for growing dahlias is called topping off.  Topping off is where you snip off the top of the dahlia when it’s about 1 1/2 feet tall.  You’re going to be cutting off the first bloom.  This will produce a more shapely plant with more flowers.  A good resource for buying dahlias online is Swan Island Dahlias.  Click HERE to watch a very short video from Swan Island Dahlias that demonstrates how to top off your dahlia.
  • Lastly, don’t forget to regularly deadhead your dahlia.  Deadheading just means to cut off the spent flowers.  You want your plant’s energy directed into continued growth and flower production, and not into going to seed!

Dahlias Photos

Here are some photographs of my garden last year.  One of my favorite dahlias I’ve ever grown is the tall red one shown in the upper left hand corner.  This is a variety called “Groovy” and I purchased it from Swan Island Dahlias.  It was a veritable flower factor all summer long.  The flowers are on the smaller end, but the color is vibrant, especially set against the stunning dark foliage.  It was the first dahlia to bloom in my garden last year and it was a workhorse all summer.

The beautiful dinner plate type dahlia below is a variety called Spartacus.  The blooms are HUGE.  This plant will require plenty of support and staking so be sure to keep up with it so it doesn’t topple over.  It’s a very vigorous grower and the blooms are definitely showstoppers!

My “wall” of dahlias below can be see on the right hand side of the picture.  This is my garden on July 31st, 2016.

Another one of my favorite dahlias is Cornell, pictured below.  This is a pompom type bloom.

I hope you’ve enjoyed this post and learned a few new things that you can apply in your own garden.  If you’ve never grown a dahlia before, go try one out!