How to Dig Up and Store Dahlia Tubers for Winter

Dahlias are the showstoppers of the summer garden, with their bold blooms adding a splash of color and drama to any space. But as the colder months roll in, many gardeners are left wondering what to do with their precious dahlia tubers. Should you dig them up or leave them in the ground? And if you do dig them up, what’s the best way to store them so they’re ready to go when spring arrives?

In this post, I’ll walk you through the reasons for lifting dahlia tubers, step-by-step instructions on how to dig them up, and tips on storing them over winter so you can enjoy their spectacular blooms again next year.

To Dig or Not to Dig?

The decision to dig up your dahlias depends on a few factors, mainly your local climate and how you’d like to manage your dahlias long-term.

When to Dig Up Dahlia Tubers

Freezing temperatures can damage or even kill the tubers if they are left in the ground unprotected, however, this is really only the case in the much colder regions like parts of the US and Canada. In the UK, it’s unlikely enough to get colder enough and for the ground to freeze enough to kill dahlia tubers. However, if you live somewhere like Scotland, you may want to add the issue of wet ground over the colder months. This will definitely cause you problems, so generally, digging up the tubers is the safer bet.

Heavy, wet winter soils can cause the tubers to rot, and they may suffer from pests and diseases if left unprotected. For a bit of extra insurance, many gardeners in temperate climates still lift their dahlias, store them indoors, and replant in the spring.

Why You Might Skip the Digging

In regions with mild winters or well-draining soil, you can cover your dahlia tubers with a thick layer of mulch, which provides some insulation against light frost and helps keep them safe from pests. But keep in mind that tubers left in the ground tend to produce slightly weaker plants over time, as they’re more vulnerable to rot and damage. If you’re after a more vigorous plant, digging them up each year and storing them properly over winter is worth the extra effort.

How to Dig Up Dahlia Tubers: A Step-by-Step Guide

Once you’ve decided to dig up your tubers, it’s all about timing and handling them with care. Here’s a step-by-step guide to help you get it right.

1. Wait for the First Frost

Start by waiting for the first frost to hit. Once you see the foliage on your dahlias blackening and wilting, you’ll know the time has come. The frost signals to the plant that the growing season is over, and it’s an ideal time to dig up the tubers as they’ll be dormant.

2. Cut Back the Foliage

Using sharp, clean secateurs, cut back the dahlia stems to about 10-15 cm (4-6 inches) above the ground. This makes it easier to handle the plant and focus on the tubers themselves. Be careful here, as rough handling can damage the tubers, especially the “neck” area where the stem meets the tubers.

3. Loosen the Soil Around the Tubers

Using a garden fork, loosen the soil around the base of the plant, starting about 30 cm (12 inches) away from the main stem. This helps prevent accidentally spearing the tubers, which can cause rot in storage. Gently lift the clump of tubers from the ground, trying to keep the entire clump intact.

4. Clean Off Excess Soil

Shake off loose soil from the tubers, being careful not to scrub too hard, as fresh cuts or abrasions can invite rot. Some gardeners choose to rinse the tubers with a gentle spray, but if your soil is already quite dry, shaking and brushing off loose soil is usually sufficient.

5. Let Them Dry (Cure) Before Storage

Once the tubers are out of the ground, they need to dry out, or “cure,” to toughen up the skin and reduce the chance of rot during storage. Lay the clumps out in a cool, dry, well-ventilated area for a few days to allow them to dry naturally. Avoid direct sunlight, as it can cause uneven drying.

Preparing and Storing Dahlia Tubers for Winter

Proper storage is key to ensuring your dahlias survive the winter in good condition. Here are the main steps:

1. Divide and Inspect the Tubers

Once they’re dry, inspect each clump carefully. Remove any damaged or diseased tubers, as these can spread rot to healthy ones in storage. Look out for any signs of soft spots, mold, or shriveled tubers, as these are indicators that the tuber may not make it through the winter. If you have a large clump, you can divide it into smaller sections to make storage easier.

To divide, locate the “eye” of each tuber (small growing points near the neck where next year’s stems will emerge) and separate each tuber with at least one eye attached. Use a clean, sharp knife or secateurs for clean cuts and to avoid damaging the tubers.

2. Choose a Storage Method

Dahlia tubers need a cool, dark, and moderately humid environment to make it through the winter. Aim for a space that stays between 4-10°C (40-50°F). An unheated basement, cellar, or garage can work well if it doesn’t dip below freezing.

• Box or Bin Method: Place tubers in a cardboard box or plastic bin, layering them with sawdust, peat moss, or vermiculite to absorb excess moisture and prevent rot.
• Paper Method: If you’re tight on space, you can store individual tubers in paper bags or wrapped in newspaper with a bit of dry vermiculite or sand. This method allows airflow while keeping moisture levels in check.

3. Check on Your Tubers Regularly

Even with the best storage conditions, dahlia tubers should be checked about once a month throughout the winter. Look for any signs of shrivelling (indicating they’re too dry) or rot (if too moist). Adjust the moisture levels as needed. If tubers look overly dry, mist them lightly with water. For rotting tubers, remove any affected ones to prevent the spread.

Final Thoughts

Digging up and storing dahlia tubers does take a bit of work, but it’s well worth it for the reward of healthy, vigorous plants next year. By following these steps and storing them properly, you can keep your dahlias safe and ready to grace your garden with their beauty again when the warm weather returns. So, grab those secateurs and garden fork, and let’s get those dahlias tucked in for the winter!