When to Dig Up Your Flower Tubers: Considerations for Your Climate

Knowing the optimal time to dig up your flower tubers can help you protect your plants for the growing season ahead. In this article, gardening enthusiast Lindsay Miller delves into the details to keep your beloved blooms thriving year after year

Tall stalks of Canna indica with large, peach and orange petals, surrounded by lush green leaves, rise among a colorful mix of smaller, red blooms and green shrubs in the background, basking in sunlight.

Contents

Whether you’re cultivating dahlias, cannas, or callas, knowing the right time to dig up your flower tubers can be the difference between a lush garden and a season of missed opportunities!

The best time to dig up tender tubers largely depends on the type of plant, your local climate and, of course, your hardiness or growing zone. In the warmest regions, you might have the luxury of leaving them in the ground year-round. However, in areas with harsh, freezing winters, tender species need to be dug up after the first light frost. This allows the plants to mature and store enough nutrients for the following year.

Read on to dig up a few tips to determine when you should dig up your flower tubers.

Hardy vs. Tender Tubers

A vibrant mix of purple, yellow, and white crocus blooms with delicate, cup-shaped petals rise from a grassy field, accented by slender green leaves, with blurred greenery and additional crocus plants in the background.
They can typically be classified as either hardy or tender.

Tubers and other plant storage structures like corms, rhizomes, and of course, true bulbs are commonly lumped under the general term “bulbs”. Bulbs can typically be classified as either hardy or tender. Hardy bulbs can be left in the ground year-round, as they can survive cold winters with long stretches of below-freezing temperatures. Hardy bulbs actually require a cold period to break their dormancy and begin sprouting. These are generally spring- and early summer- flowering plants like daffodils, tulips, crocuses, allium, and hyacinths.

Tender bulbs, tubers, corms, and roots include summer- and early fall- flowering plants such as dahlias, canna lilies, caladiums, calla lilies, tuberous begonias, and freesia. Most of these plants are native to tropical or semi-tropical environments and they cannot survive a hard freeze. 

Temperature

The decision depends mostly on the temperatures in your area.

Colder Climates

Large, round clusters of tiny purple blossoms form dense spheres atop tall, slender stalks, set against a background of soft-focus greenery and additional purple blooms, creating a striking visual contrast.
In colder climates, dig them up after the first frost, but before the ground freezes solid.

First, know your zone and frost dates! Grow zones, also known as hardiness zones, indicate a location’s average low temperature.

As a zone 4 gardener, I am well-versed in the “move it or lose it” philosophy surrounding my tender tubers. By mid fall, I need to decide if I will be digging up and storing my dahlias and gladiolus, or if I’m ok losing this season’s flower tubers. In colder climates, dig them up after the first frost, but before the ground freezes solid. Here in zone 4, that usually occurs in late October (I grew up where it was very normal to wear entire snowsuits under your Halloween costume). However, zone 7 gardeners may not receive frost until early November.

A light frost will kill the foliage. This triggers the plant to head into dormancy and will be your cue that it’s time to pull up your tubers. Use a broadfork or shovel to dig around the plants, being careful not to cut off the roots. Trim all the upper dead foliage off to avoid rot spreading to the tuber. Brush the loose soil off of the tubers and let them cure, or dry, for a few days to a few weeks (depending on your climate) before storing them.

Tubers are best stored in a cool, dark location. Basements and garages are great as long as they remain frost-free. Storage temperatures should generally be between 40-50°F (4-10°C). Warmer temperatures can promote fungi to form or encourage tubers to emerge from their winter dormancy and start sprouting. Periodically check stored bulbs and tubers and roots during the storage season.

Warmer Climates

Fiery red, spiky blooms of Dahlia pinnata emerge from tall, green stems, accompanied by long, pointed green leaves, growing amidst a colorful backdrop of smaller, scattered plants and verdant foliage.
Gardeners in warm regions have the option to leave them in the ground year-round.

Gardeners in warm regions have the option to leave them in the ground year-round. Dahlias, for example, are perennially hardy in zones 8-11. This means that come fall, tubers planted in these zones can remain in the ground.

Tender BulbsHardiness
DahliasZones 8-11
CannasZones 8-11
Tuberous begoniasZones 10-11
CaladiumsZones 9-11
Calla liliesZones 8-11
FreesiaZones 9-11

Gardeners right on the northern cusp of a plant’s hardiness range should consider a healthy layer of mulch as an added bit of protection. Wood chips, chopped leaves, and bark mulch are all excellent organic mulch options. Once new shoots begin to emerge in the spring, simply move the mulch aside.

Even if you can safely keep your tubers in the ground all year long, it is still wise to dig them up every few years to divide them. Dividing rejuvenates the plant and promotes flowering. If a clump of tubers is not divided, many stems will emerge next spring instead of a vigorous individual plant. Dividing is also a great way to increase your number of plants!

Moisture

A green, stemmed plant with elongated leaves is partially uprooted, revealing dark, decayed roots surrounded by clumps of black soil, next to an overturned white planter, all displayed on a light surface with scattered dirt.
Proper drainage and dry conditions are key to preventing rot and frost damage in overwintering plants.

Unfortunately, gardeners cannot go strictly by their grow zone alone. Proper drainage and dry conditions are key to preventing rot and frost damage in overwintering tubers. Heavy soil combined with wet winter weather, even if not particularly cold, could cause your tubers to rot.

Let’s go back to our dahlia tuber example. If you are growing dahlias in zone 8 and you have sandy, well-drained soil coupled with relatively dry winter weather, you may be able to get away with leaving the tubers in the ground. However zone 8 gardeners that experience long, wet winters will want to dig up their tubers after the first light frost hits. 

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Key Takeaways

Your local climate and flower hardiness are the key determinants of whether or not you should dig up tubers. Whether you’re dealing with freezing winters or basking in milder temps, timing makes all the difference!

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Dahlia tubers stored in a black plastic container in an autumn garden, prepared for overwintering.

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