When and How to Plant Dahlias

Dahlias can make your garden look extra stunning with big, bold, and colorful flowers. They come in many different colors and shapes, like a little flower festival when they are blooming.

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If you wish to see these beauties right in your backyard, keep scrolling down and reading my guide on “When and how to plant Dahlias”. Let’s grow something amazing together!

The Best Time of Year to Plant Dahlias

Indoors	Outdoors
Plant dahlia tubers about 4-6 weeks before the last frost	Wait until the frost has completely gone before growing dahlias
*A quick tip:* Dahlias can’t stand colder temperatures than USDA zone 8. If you live in such a cold place, dig them up, store them, and plant them later!

How To Choose & Tag Dahlia Tubers

We grow dahlias by tubers. So the first thing to do is choose the right tubers and learn how to monitor them.

Choose Healthy Tubers

Always seek out ones that are plump and firm, similar to a quality sweet potato. Avoid those that have moldy areas, appear wrinkled, or feel mushy.

Healthy tubers preferably have an eye – the tiny bump where new growth starts. No eye means no flowers later.

Bonus Tip:Read the plant label carefully. It will let you know a lot of information, such as how tall the plant will grow, what size blossoms to anticipate, and if it is worthwhile to save for the following season.

Tag & Track Different Varieties

Since all Dahlia tubers look quite the same, you must tag them to keep track.

Here’s how I keep my tubers organized:

Mark on tubers: Use a permanent marker to write directly on the dry tubers. A simple name or code works. Just remember to jot down what your code means!
Tag your plants: Attach tags to the support stakes for easy identification. You can also write a name or code on the pots.

It is very flexible to grow dahlias. You can plant them almost anywhere. Let’s start with how to grow your dahlias indoors.

Grow Dahlias Indoors

If you expect to see your dahlias bloom early, get them started indoors (a month sooner). Here’s how to do it:

Pick the Right Time

Start 4 to 6 weeks before the last expected frost in your area.

Choose the Right Pot

Pick a wide and deep container. It should be about 6 inches deep or bigger. I love using bigger containers because they double as outdoor planters later.

Plant the Tuber

Add fresh, well-draining potting mix to the pot.
Any visible “eyes” or sprouts are facing up while the tuber is flat on the ground.
Plant about 6 inches deep
Water the soil lightly to let it settle.

Give Them Some Light

Pick a place where dahlias can get 6 hours of direct sunlight (at least) every day. If not, put it under the grow lights.

Water Just Right

Keep the soil lightly moist but never soggy.

Harden Them Off

Gradually expose your dahlias to the outdoors after the last frost. Start with a couple of hours a day in a shaded, sheltered spot and slowly increase their time outside over a week.

Decide on Their Summer Home

Now you can either:

For patios or balconies, keep dwarf varieties in their pots.
Move the larger varieties into your garden beds so they can have room to grow and shine.

Plant Dahlias Outdoors

When the weather gets warmer, it’s time to plan your favorite dahlias outdoors!

Wait for the Right Time

After the last frost, when soil temperatures stay around 60°F (16°C) for several days in a row.

Pick the Perfect Spot

One with plenty of sunlight in the morning and some shade in the afternoon.
The soil is rich, loose, and well-drained

Dig the Hole

About 12 inches wide and 6 inches deep for holes
Keep the holes 1-3 feet apart. This depends on the dahlia size variety (check it on the labels)

Plant the Tuber

Lay the dahlia tuber flat with the eye/sprout facing up in the hole
Cover it gently with soil

Pro tip: If your tuber already has a sprout and leaves, carefully remove the lowest leaves (small baby ones). Then, place it with the first real leaves above the ground surface.

Hold Off on Watering

Don’t water straight after planting if your soil is already moist and rain is often. Water more frequently until you notice shoots growing.

Dahlia Supports:
Tall varieties will need support to keep them from falling over. This is how you can do your own Dahlia supports:
– Materials: metal rods, wood stakes, or pipes.
– Height: Should be as tall as the expected height of the dahlias, plus one foot under the soil.
– Position: Place the stake right beside the tuber’s eye
– Support: Loosely tie twine around the stem and stake as the plant grows up.

Grow Dahlias In Containers

Likewise, you can plant them directly into pots following the last frost or start them indoors in the early spring.

With containers, you can easily dig up and store your tubers at the end of the season. Plus, you can also reposition them to avoid heat waves or intense rain as necessary.

Blooming Time Dahlia flowers need 90-120 days to bloom.

Bottom Line

That is everything you need to know about when and how to plant dahlias! The point is to choose the right time to start your loving dahlias – they don’t like too cold weather.

Trust me — once those blooms start showing off, you’ll be hooked!