Growing Dahlias in Pots
Container Gardening,  Cut Flowers,  Gardens

Growing Dahlias in Pots

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Ever since I discovered cut flowers I have been obsessed with Dahlias. I just love the look of them, the color and a bunch together in a bouquet makes my heart sing. But the thought of over wintering the tubers and keeping the conditions just right so they don’t rot scares the crap out of me.  But I still want to grow them. Lol Was growing Dahlias in pots a thing?

Like a lot of things early in our homestead I kept certain dreams on hold because I didn’t want to invest time and money into a place that we knew we were growing out of. I have one of those personalities though that when I get something in my head I just have to have it, so I started researching other ways to achieve our goals. And come to find out many of the things that I wanted to grow could be grown in POTS!!  And those pots could be taken with us when we decided to move. 

I moved up my Dahlias dream. Bought a few pots and starting Growing Dahlias in Pots!!

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Growing Dahlias in Pots

Dahlias grow well in pots, though you need to be very careful not to let them repeatedly dry out. They also will need to be regularly fertilized during the growing season, and many will need to be staked so they don’t fall over. It’s also a good idea to put the taller varieties in heavy pots, so the wind doesn’t blow them over.

You can buy dahlia tubers online or in nurseries and some big box stores. We got ours at Lowes. Many nurseries also sell dahlias already started in containers. Dahlias come in a huge range of flower size as well as plant size. If you are looking for enormous flowers, look for “dinner plate” dahlias. If you are looking for shorter plants look for miniatures, or “low growing” dahlias.

To see a complete plant profile check out – How to Grow Dahlias

Growing Dahlias in Pots

Planting in Pots

If you live in a colder climate and want your dahlias to bloom earlier, you can plant them indoors about 6 weeks before the last frost. However, if you do plant them inside, it’s a good idea to provide supplemental lighting once the plant breaks through to the surface of your soil. For lighting, you can either use shop lights fitted with one cool and one warm fluorescent bulb or special “grow lights.”​

If started inside, place the containers under plant lights. The dahlias should have light from above to keep them from bending towards the light of a window and to grow compactly. Set the lights about six inches from the tops of the pots of newly planted tubers. Raise the lights as the plants grow. Suspending the lamps from chains on hooks makes them easier to raise and lower.

If you are starting your dahlias in pots outside, wait until all danger of frost has passed or make sure you can move your pot inside if frost is predicted.

For most dahlias, you want a fairly large pot, though it doesn’t need to be very deep. Many varieties would do well in a 12- to 14-inch diameter pot which is also at least 12 inches deep. Also, make sure the pot has good drainage because the tubers will rot if left to sit in water.

I use heavy-weight, sturdy, plastic pots in which I can drill holes for staking. The diameters of pots I usually use are 8 1/2-inches and 10 1/2-inches. I have a few 11-inch and 12-inch pots for planting really long tubers. For base stability, I prefer the azalea style of pot, meaning that a pot has a short height in relation to its diameter which makes it look short and squat, as opposed to a tall, skinny looking container. I do not match pot size to the final bloom size, because miniature flowers could be on a tall bush and giant blooms could be on a short plant. I match the pot to how tall the plant could be or the length of the tuber.

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Choose a good all-purpose, fast-draining potting mix and stir in a slow-release fertilizer, following the label for directions on quantity. Whatever potting mix you want to use, make sure it is very loose whether wet or dry. Make sure the potting soil does not have clay in it. Dahlias do not like to grow in clay soil. The clay turns the soil into mud when wet or into a block of cement if allowed to dry out.

Dahlia tubers can be a bit unwieldy and large so, unless you are going to separate them, you will need to be careful when planting in containers. In the container, if the tuber is placed in the bottom of the pot and then the potting soil is immediately filled in up to 1-inch below the rim and then is thoroughly watered, the tuber could very likely rot. Planted higher up to prevent rotting, the tuber would become exposed to the surface and the base of the stalk would be sitting on the surface of the soil. Then the stalk could the be easily broken off from the tuber. 

When planted in the ground, directions usually state to dig a hole about five to six inches deep and fill in the hole with soil as the plant grows. I learned the best way to plant the container grown dahlia is to plant the tuber by following the same method: plant the tuber deeply and slowly add more potting soil as the plant grows.

Growing Dahlias in Pots

Make sure that the potting mix surrounds all the parts of the tuber without leaving any air pockets, and that the top of the plant is pointing upward (look for eyes, like you would find on a potato or where they stem used to come out of the bunch). Mound a few inches of potting soil on the bottom of the pot, forming a little bit of a hill and balance the tuber on the mound. Then carefully fill in around the tuber with potting soil, firming it around the tuber gently to avoid breaking them.

Care and Maintenance

Dahlias like full sun, though don’t like to get searingly hot. If you live in a warm climate or your pot is in a hot spot (in a corner or on concrete where the surface gets hot) move your pot into a shady spot during the heat of the day.

An important “secret” ingredient I stir into the potting soil when I plant the tuber is a product made of acrylic copolymer crystals. The copolymer crystals absorb water and release it to the roots of the plant when the soil dries out. They protect the plant from being overwatered or dying in dry soil. The products I have used are TerraSorb™ and Soil Moist™. They provide the added benefit of keeping the roots cool during a hot day, and from keeping the soil (and tubers) from freezing when the frost kills the top of the plants in the fall. I use the copolymer crystals in all my containers of non-cactus plants.

Keep the soil moist, but not wet. Most dahlias will have to be staked so they don’t fall over. Also, depending on the depth of your pot, a single stake might not do the trick of holding up the plant either—particularly in a stiff breeze. You can make a teepee out of bamboo. 

When the plants get at least three or four sets of leaves, pinch out the growth tip of the stalk. Pinching helps to make a bushier, sturdier plant. It does not delay the blooming time of the plant, but the plant does make more flowers. When I don’t pinch, I usually get tall, skinny plants.

Also, for more flowers, deadhead regularly.

Growing Dahlias in Pots

The best thing about container gardening is that the plants can be moved! The ones in flower can be turned around or moved to the front for the best flower show, the ones growing too tall go to the back, or the sun stressed ones can be moved to a shadier location. When dark thunderstorm clouds are seen moving in our direction, I move the plants next to the house, under the eaves, until the storm passes or until the next morning. In early September, when there is an early frost I make a mad dash out and bring inside the dahlias which are in full bloom or have a lot of promising buds on them. After that first frigid spell, the temperatures usually warm up again; the plants go outside and give us another month of beautiful dahlia flowers.

Overwintering Dahlias

If you live in a cold climate it’s best to overwinter dahlias. Wait until after a couple of frosts. Then, cut off the dead foliage a few inches about the soil and let the pot dry out in your garage or shed. At this point, carefully dig up the tubers and brush off all the extra dirt. Put them in a cardboard box and store them in dry, cool conditions, such as an open basement with good air circulation. In the spring, carefully inspect the tubers and replant only those that are firm and not desiccated or soft.

Growing Dahlias in Pots

I am still a little scared of overwintering Dahlias but the flowers were worth the extra effort and I can’t wait to grow more next year and to even have a full raised bed of them at our future farmhouse.  If you are hesitant about starting something new at your farmhouse JUST DO IT!!  You will most likely make a few mistakes along the way but it will be worth it and you will learn so much.  I highly suggest you start growing Dahlias in Pots!!

Get Your Kids Involved...

Our kids are involved in every aspect of our homestead.  And Henleigh is particularly fond of the flowers. We teach her about caring for them and their benefits, by reading. Here are some books about gardening for kids. 

What Other Things Will Grow in Pots?