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Garden Help Desk: Proper storage keeps dahlia tubers ready for spring planting

By USU Extension - Special to the Daily Herald | Nov 18, 2023
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Dahlia blooms come in many sizes, shapes, and colors.
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Just like all dahlias in our area, these little pompon dahlias won't survive the winter unless their tuberous roots are dug up and stored in a cool location where they won't freeze.
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These container garden dahlias were cut back and overwintered in an insulated garage and then set back out in the early summer for another season of blooms.

I planted some dahlias for the first time last spring. I heard that if I wanted to grow them again next year, I could save them by digging up the bulbs before they froze. I did that and put the clumps into a bucket in my laundry room but have been too busy until now to take care of them. What should I do with them?

Dahlias grow from tuberous roots, a little different than bulbs, and you’ll be handling them a little differently than you would bulbs. Hopefully you dug up the stems and roots together because the roots won’t produce new growth next year unless there is some stem still attached to them.

Gently shake off loose soil. You can rinse off the clump to remove any remaining soil, but it’s important to let the clumps dry completely afterward. Many gardeners simply store the clumps of tubers without rinsing away the soil. Either way, handle the clump carefully to avoid breaking away the tops or damaging the skin of the tubers.

The tubers you save should be firm and light brown in color. Sunken, dark, soft or watery-looking spots are signs of frost damage or disease.

You can divide the tubers before you store them or wait until spring. If your dahlia only has a few small tubers, you can keep the clump the way it is. If your dahlia was very vigorous and you have a large, crowded clump of nice, plump tubers, you should divide the clump. Use a clean, sharp knife for the job. Each tuber needs to have a piece of the neck and some “eyes” (buds) or it won’t grow.

To store the tubers, you can spread them out in boxes or crates, put them in paper bags, or wrap them in newspaper or anything else that provides a little air circulation and keeps the tubers from touching each other. Keep them in a cool, dark (but not freezing) place with good air circulation where moisture won’t condense on them.

Check the tubers every month or so until planting time next spring and discard any that show signs of decay.

If dahlias are grown in a container, you can simply cut back the stems to about two to three inches tall and store the container in a cold place where the dahlias will remain dormant without freezing. If the dahlias were crowded in their container, you can tip out the root ball and separate some of the roots with their stems before replanting.

My walnut tree has finally started dropping its leaves. Can I put them in my garden? I’ve heard they can poison some plants, but I hate to waste all that organic matter by sending it to the landfill. Is it better to put the leaves into my compost pile instead, or should I not use them at all?

It’s unlikely you need to be concerned about this. Many gardeners worry about using leaves or wood chips from walnut trees because juglone, a compound found naturally in walnut trees, may inhibit the growth of other plants. The effects of juglone have been demonstrated in laboratory research, but limited research “out in the field” has been inconclusive. There’s doesn’t seem to be clear evidence that juglone enters the soil and damages plants the way it does when it’s applied to seedlings and young plants in a laboratory setting.

Luckily for gardeners who need to clean up the fallen leaves from their walnut trees, juglone breaks down in a few months because of microbial activity in compost piles or with simple of exposure to the elements.

The leaflets from walnut leaves are large. They’ll compost more easily if you use a shredder or the bagging attachment on your mower to speed up the process. Once composting is complete, you can use that compost the way you’d use any other compost.

The wood from walnut trees is very low in juglone, so wood chips from walnut prunings can be safely used as mulch over the soil in your shrub and flower beds. Just like the chips from any other tree species, they shouldn’t be mixed into the soil.


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