Don’t Plant Dahlias Before You’ve Made This One Vital Check!

Whether you’ve ordered new dahlia tubers or have some stored from last year, it’s always a smart move to check they're viable before planting. In spring, it’s common to see dahlia tubers damaged from being jostled around in the postage system, garden center or your garage.

A single tuber will often become detached from the main cluster, or might see a dahlia tuber with a damaged neck. Some will still have everything they need to grow, giving you an extra Dahlia plant for free; others won’t be viable and will simply rot in the ground, wasting your time and garden space.

Luckily, there’s a really easy way to tell if a dahlia tuber is viable. These fabulous flowers aren’t cheap, so it’s a test that’s well worth doing before planting dahlia tubers.

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How to Tell If A Dahlia Tuber is Viable

1. Check the Crown is Intact

If one tuber has become detached from the main cluster, look to see where it has snapped off. A viable dahlia tuber has three parts: the plump, fleshy body where its energy is stored; a knobbly bit at the top called the crown, and a narrower neck connecting the two.

Take a look at these tubers – they all have a knobbly crown at the top of their necks, and it’s from here that the stems will grow. Different varieties come in different shapes but they all should have a knobbly woody collar at the top of the neck.

So, if a tuber has snapped off below this all-important crown – and that’s pretty common as the necks are so narrow – it’s not viable. The rest of the cluster will be fine, but not this damaged, detached tuber.

You can see here how the crowns all attach to last year's stem. Planting this cluster as a whole will grow a large, strong plant, but each tuber has all it needs to survive on its own, too, if it becomes separated, as long as its all-important crown is intact.

2. Look For an Eye

If the crown is intact, the next stage is to look for an eye. This is the point on the crown that the stem grows from, and there may be more than one.

If your tuber is still dormant – and if you recently bought yours then it might still be, even in May, as they’re often kept in cold storage – then the eye will look like a little round bump, pimple or wart. It’ll be the same color as the crown, but slightly raised. If you can’t spot an eye, try brushing off old soil with a dry paintbrush then slowly rotate the crown under a desk light, and a shadow of the raised area may reveal one.

The eyes might be very obvious, too. Once a tuber wakes from dormancy, the eyes start to swell and some can turn a pink or green color. The eye may have even sprouted and you’ll see the shoot.

If your tuber has at least one eye, it’s good to plant.

3. Squeeze the Tuber

If there's no sign of an eye, give the body of the tuber a gentle squeeze. If it feels at all mushy or soft, throw it away.

4. Give it One Last Chance

If the tuber body is firm, you can give your tuber one last chance by laying it horizontally in a tray of just-moist potting mix and barely covering it with a little more soil. Keep this in a warm, light spot that’s at least 65°F and within two weeks you should see at least one stem growing from the crown. If you see nothing after three weeks, examine the tuber again. You should at least be able to spot some swelling eyes at this point so, if you can’t, consign your tuber to the compost heap.

What About Tubers That Are Still Attached?

Clusters of tubers still attached to last year’s stem(s) will have their crowns intact so are good to plant. Just give each tuber a gentle squeeze and, if you discover any that feel mushy, remove them from the cluster by cutting at the neck with hand pruners.

Don't worry if any tubers are shrivelled. As long as they're firm, they're likely fine.

What if the Tuber Neck is Just Damaged?

It’s common to see tubers still attached to the main cluster but with damaged necks. If it’s just the skin that’s broken, the damage is cosmetic and the tuber is likely fine. However, if the damage is deeper and the tuber is hanging by a few fibrous strands, it’s best to snip it off at the neck with hand pruners.