Why Didn't My Dahlia Come Up?

It's usually around this time of year that people start asking, "I planted my dahlia tubers X weeks ago. Why haven't some of them come up?"

Waiting for your dahlias to sprout has to be one of the hardest parts of growing these gorgeous flowers, especially when it's your first time. You're staring at bare soil or mulch, thinking, "Ooooh, is that it?" Then you realize, "Nope. That's just a weed."

There are several possible reasons.

1. Your tuber is growing underground but just hasn't broken through the soil yet.

The tuber may be busy forming roots and sending up a shoot from its eye, but the sprout simply hasn't reached the surface.

In the years since I first started growing dahlias, I've found that some varieties are much more eager to get going in spring than others. Some seem to pop up almost immediately, sometimes within a week or two of planting. Others take forever. In some cases, it can be six weeks or even longer before you see those distinctive dahlia leaves emerge from the soil.

2. Your tuber didn't have an eye.

If a dahlia tuber doesn't have an eye, the growing point that produces the sprout, it will never grow into a plant. Even if the tuber looked plump and healthy. Even if you saw fine roots developing.

Reputable sellers guarantee that their tubers will have at least one viable eye, but mistakes do happen. Or, if you saved your own tubers and replanted them, perhaps what you thought was an eye was actually just a tiny speck of dirt.

3. The tuber was dead when you planted it.

If a tuber dries out completely or freezes, it will die. If you saw a sprout already beginning to grow when you planted it, you know the tuber was alive. But if there was no visible sprout and it looked extremely shriveled, it's possible that it had already died.

The encouraging news is that tubers that look pretty rough can often still produce beautiful, vigorous plants as long as they have a little life left in them. But if the tuber is completely dead, there's nothing it can do.

Unfortunately, I've even seen dead dahlia tubers for sale at big box stores. I always feel bad for the unsuspecting gardeners who buy them, plant them, and then conclude, "I guess dahlias are just too hard to grow."

4. The tuber was alive when you planted it but rotted in the ground.

Unfortunately, this does happen, especially if the soil stays too wet before the tuber has sprouted. This is one of the reasons I recommend planting in well-drained soil and holding off on watering until you actually see a sprout emerge.

Several years ago, I toured the garden of the then-president of the Philadelphia Area Dahlia Society, and he told me that he expects 15 to 20 percent of his dahlias not to come up each year.

That surprised me at the time, but the truth is that a certain percentage of dahlias simply won't make it. Sad, but true.

So what should you do?

Personally, I don't think there's any reason to worry until at least four or five weeks after planting. If it's been six or seven weeks and your tuber still hasn't sprouted, I'd go ahead and dig it up to investigate.

You might find that it has actually sprouted underground and just hasn't quite broken the surface yet. In that case, you can gently replant it.

Or you might find a firm tuber that never sprouted, one that's extremely shriveled and clearly dead, or one that has rotted away completely.

Whatever you find, it's useful information. Every tuber you dig up teaches you a little more about how dahlias grow, and that knowledge will make you a better gardener the next time around.

One final word of encouragement: don't panic if one or two tubers don't come up. Even experienced dahlia growers lose a few every year. Sometimes patience is all that's needed, and sometimes nature simply has other plans.