How to Grow Dahlias

How to Grow Dahlias

Grow Dahlias in a garden, in a pot, on a balcony, or patio. Dahlias are an easy flower to grow for beginning to expert gardeners. I have enjoyed growing dahlias and they will forever be a part of my garden. Read on and learn how easily you can incorporate dahlias into your garden.

Dahlias are not only extremely easy and inexpensive to grow, but the bloom payoff is enormous. The dinner plate dahlia can produce blooms that are 10-12 inches across. My first dahlia was a Kelvin Floodlight. It was my first plant and I didn’t do anything special to it. The picture below is the first bloom.

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How to Grow Dahlias – Objectives:

  1. Necessary supplies to grow dahlias
  2. Preparing the soil
  3. Pruning Instructions
  4. Fertilizing and watering
  5. Pro-dahlia growing tips
  6. Dahlia problems
  7. Cutting dahlias
  8. Winterizing dahlias
  9. Conclusions
Kelvin Floodlight Dinnerplate Dahlia
Kelvin Floodlight Dahlia in the Garden of Aquarius Image credit: Garden of Aquarius

Let’s get started: How to grow dahlias

What you will need to grow dahlias:

  • Dahlia tubers
  • Garden soil or potting soil (if using a container)
  • 12 inches of garden space or a 12-inch container with good drainage
  • Bamboo pole, stick, or stake to support the dahlia
  • Miracle Grow Flower fertilizer

 

Prepare the soil

Garden planting instructions

If you are planting in the garden, be sure to plant in an area that gets a lot of sun and drains well. Read more about soil here. Dig a hole that is about 6 inches deep and wide enough for the dahlia tuber to spread out. Place the dahlia in the hole with the “eyes” looking up. Push your stake into the earth next to the dahlia tuber. Back-fill the soil into the hole. Gently press down the soil.

Container planting instructions

I love planting my dahlias in containers. Not only does it impede snails and slugs, but it also makes them mobile. So let me tell you how to do it. Make sure your container is large enough to hold enough weight so that it doesn’t blow over in the wind. The dinner plate dahlia variety can grow up to 4 ft tall. Strong winds will blow them over. It’s happened to me!

Your container should have drainage holes drilled into the bottom. Then, throw in a bunch of gravel, river stones, packing peanuts, perlite, or anything you can that will give a good 2 inches of drainage in the bottom of the pot. The idea here is that this will allow water to pass so that it doesn’t pool and rot your roots.

Add potting soil on top until you are about 6 inches from the top of the container. Place your dahlia tuber with eyes up – on the soil, then the bamboo stake should be pushed into the soil and through the drainage material for stability. Cover the dahlias with about 4 inches of soil and gently press down. Press down around the stake to make it stable. After the dahlia breaks through the soil, you can add more soil in the pot and gently press around the plant up to 2 inches. This will give the large dahlia varieties more stability. If you are planting a smaller variety, this isn’t necessary.

Dahlia pruning instructions

Once your dahlia breaks through the soil you will have one or more plants coming up. Some of mine produce one stalk, others produce 2-4 at times. If one of my dahlias produces just one stalk, I like to prune it early to get more flowers later on.

The entire point of a dahlia plant is the flower. Pruning will help you grow more dahlia blooms. You want to know how to grow the most flowers, right?

I experimented one year with two of the same dahlia tubers. One I pruned and the other I didn’t. The one that I pruned exploded that year with blooms. I’m a believer. Let’s get pruning.

Look at the infographic below to see how to identify your dahlias sets of leaves. Once your dahlia has 4 sets of leaves you will want to pinch off the 4th set at the base of the leaves. After doing this, in a few days the plant will heal that spot and shoot out two stems around the pruning site. This will give you two growing tips instead of one.

dahlia pruning infographic
Dahlia pruning infographic. Image credit Garden of Aquarius

Feeding and watering your growing dahlias

Don’t let your dahlias dry out. This is especially prone to happen when you plant them in containers. Containers heat up and dry out faster than soil that is in the ground.

I like to fertilize my dahlias with Miracle Grow every 2-3 weeks once they have started blooming. You can use any garden fertilizer with high phosphorous content. Avoid those with a high nitrogen content, nitrogen encourages green growth, phosphorous encourages blooms. Fertilizers are labeled like this “12-12-12”. The first number is Nitrogen, the second number is Phosphorous, and the third number is Potassium.

I recommend this Miracle Grow that has 10-52-10, a very high phosphorous amount for an enormous amount of dahlia blooms. I reconstitute the powder in a watering can and supplement them every couple of weeks.

Pro Dahlia Growing Tips

dahlia secondary flower bud
Dahlia secondary flower bud. Image credit: Garden of Aquarius

The picture above shows a Kelvin Floodlight dahlia with enormous 10-inch blooms. The circle shows you a secondary flower bud emerging from the same stalk as the bloom on the right. Sometimes I get multiple little flower buds from the same stalk. To send more flower power to the one main flower, I pinch these off. To do this, look at all of the buds on one stalk. Save the best and pinch the others off.

This is optional, and I suggest you experiment with one plant to see if you like your results. Trial and experimentation is a fun part of gardening. I always record these details in my gardening journal to remember what worked, what didn’t, and how I did it.

Staking your growing dahlia

Once your plant gets to be about a foot tall, you will start to find the need to stake it for support. Let me say that the decorative and pompom dahlias will not likely need this. They grow to about 2 ft. tall and usually are pretty stable on their own. The dinnerplate variety has grown to an excess of 4 foot tall in my garden with stalks 2-3 inches in diameter.

I used to call this one dahlia, my Frankenstein plant. She was freakishly huge in plant trunk and in flower.

My Frankenstein dahlia with an enormous stalk
My Frankenstein dahlia with an enormous stalk. Image credit: Garden of Aquarius

To stake your dahlias, simply use twine or garden twist ties to gently, but snugly attach the main stalk to the stake and tie or twist off. You will likely need to do this multiple times especially if you have a particularly heavy growth tip with blooms. Just loosely tie them to the stake for support.

Avoid using wire or tying too tightly, this will cut into the plant stalk and cause damage. It might even cut through your stalk if the winds blows too hard. Be gentle with staking your dahlias.

Problems growing dahlias

Growing dahlias has been pretty problem-free. I have never had any issue with disease. (knock on wood) The only predator here in Zone 9 is the snail. If you look in the bottom right-hand corner of the above picture you will see snail damage.

Snails may be slow, but they are hard workers. They can eat a small plant in a day or strip a branch of leaves if left to their own devices. I am not squeamish at all at plucking them right off of my plants. After plucking them off, you can toss them in a bucket of salty water or beer. Plain water does nothing, they crawl right out.

Snails bother your dahlias less when they are in pots. It’s a long haul up the side of an 18 inch pot, but they do try. Check under your leaves for snails hiding in your pots.

Snails are active at dusk and in the early morning. I walk through the garden early morning looking for the little critters and remove as many as I can find. I also used a homemade beer trap last year. It caught dozens of snails a week.

Lavender aromatherapy snail.  Image credit: Garden of Aquarius
Lavender aromatherapy snail. Image credit: Garden of Aquarius

Cutting dahlias

Now for the moment where all of your hard work pays off. Your
pièce de ré·sis·tance! Cutting off that first dahlia bloom and then placing it in the perfect vase is that moment. Last year I had to start using anything I could find for vases because my flowers were exploding.

Invest in a nice pair of garden pruners and keep them clean in between cuttings using alcohol. Cross contamination can occur between plants and spread disease.

Several Dahlia varieties including pompom, dinnerplate, cactus, and decorative.
Several Dahlia varieties. Image credit: Garden of Aquarius

What to do with dahlias in winter

When Fall comes and the plant begins to die, just let it wilt. This is the dahlia retirement. It will send its energy back down into the tuber for next Spring. If you live in a moderate climate, they will likely come back next year.

In Florida, the winter is very wet and this causes the tubers to rot in the ground. You can cut the plant down to the ground in the winter and dig up the tuber. Just work your shovel in a circle around the plant. Make about a 10 inch trench around the plant gently digging in and loosening the soil. Gently remove the soil while you dig up the tuber.

Let the soil dry out in a dry spot outdoors. Don’t leave them sitting on concrete, this sucks all the moisture out of them. (Live and learn) After the soil is dry, brush it off with a soft brush. Then store them in a paper bag with some dry peat moss or perlite and put them in storage until next Spring.

Conclusion

It’s calming to bring nature into your home and life. While I write this I can look at the orchid blooming on my desk. If I peek over my monitor, I can see the hummingbird feeder and it’s visitors that peek back in the window at me.

Gardening is good for the psyche and the soul.

I challenge you to plant a dahlia this year and bring the wonder of nature and beauty into your life. Please post your gardening questions in the comments or email me. I hope you have enjoyed learning how to grow dahlias. Please check out my other gardening articles. and learn how to grow Plumeria, the Hawaiian lei flower.

Let’s grow together and start a flower revolution.

Dahlias and zinnias in vases
Dahlias and zinnias in vases and my desk view at the hummingbird feeder. Image credit: Garden of Aquarius

Dahila Growing Guide
Dahila Growing Guide

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6 Replies to “How to Grow Dahlias”

    1. Good Luck!!!! Let me know how it goes, I’m always available to talk Dahlias! I just planted two more yesterday called “Breakout”. I’m excited about it.

  1. Good information. I use tomato cages for my dahlias. Its windy in my area most of the time and stakes just bent with the wind.

    1. It should work the same. Take a shallow plastic container, like an empty butter tub and dig a hole in the garden the same size. Place the container in the hole until it is flush with the ground level. Fill it with beer and put a “roof” over it. I used a rock and propped up a small piece of wood. This makes it shady and keeps the rain out. Check it every few days and refill the beer as you need to. I was dumping dozens of snails out of mine each week. They loved it!

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