Common Questions about Planting Dahlia Tubers

When do I planted my dahlia tubers?

Here in Oregon, zone 8b, it is safe to plant my early to mid May. If you are in a colder region, look for your soil temperatures to be above 60 degrees. Dahlias like to be planted around the same weather conditions as tomatoes.

What do I do if my dahlia tubers has a really long sprout? Will is still grow if it breaks off?

Sometimes if the tuber has been stored a little too long, the sprout will grow quite long. If it is longer than an inch or 2, I would break it off. The stem will not be as strong if you plant it with a long sprout. Don’t worry if it broke off either. The sprout will regrow.

Should I water after planting my dahlia tuber?

You do not need to water your tuber after planting. You don’t want your tuber sitting in a lot of water before it has roots growing, otherwise it can easily rot. If you have very dry soil, you can add some water but it your soil has any moisture, I would not water.

Should I worry about it raining after planting my tubers?

If you will have lots of rain coming in the forecast, I would wait to plant my dahlias. But if it’s only a little rain, I would go ahead and plant.

If my tuber has roots but no growing eye, will it make a plant?

If a tuber does not have an eye (where the plant grows out of), it will not produce a plant. Toss the tubers if this is the case. Not all tubers will have an eye when you divide your own tuber clump.

How long does it take for green growth to appear out of the ground?

I would expect about a month. If it’s been 5-6 weeks, I would carefully dig up the tuber and check if it has rotted. If it hasn’t rotted and you can see some growth, just carefully cover up the tuber and wait.

Why are my dahlias being nibbled on after they are sprouting?

Slugs! Slugs love new dahlia growth. I would apply slug bait once you see growth poking through or just before. I like to use Sluggo or Sluggo Plus. Sluggo Plus helps kill earwigs too.

Should I add support to my dahlias?

I like to add support at planting time because then I know I won’t pierce the tuber. If you only have a few dahlias, tomato cages placed over the tuber are a good option. If you have a whole row, I like to use metal or wood stakes with some twine. Some dahlias grow quite tall so it helps them not break off in the wind and rain.

Should I fertilize at planting?

While I do add slow release fertilizer at planting, I would recommend waiting until new growth appears to fertilize-about 30 days after planting. I would use a even fertilizer to start off with like 15-15-15. But don’t apply this later in the season. Later in the season, you want a fertilizer that has a lower first number (nitrogen), and larger last 2 numbers. Like 0-10-10, or 5-10-10, etc.

I hope you have great success with your dahlias this year and enjoy beautiful blooms! If not, don’t be discouraged. Every year you will learn something new and you can take that into the next year to gain more chance of success.