How to Overwinter Tender Bulbs

If you love the seasonal display of flower bulbs in your garden and want to repeat next year, it’s worth knowing how to overwinter tender bulbs.

This is the process of selecting and storing flower bulbs that cannot survive your local winter temperatures, ready to replant them outdoors when warmer conditions return.

A simple fall gardening task that requires little time and effort and can save you money and heartache in the long run. We spoke with bulb experts and horticulturists to find out how they do it and what types of bulbs they’re essential for.

Why overwinter tender bulbs?

how to overwinter tender bulbs, gladiolus bulbs

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There are four different forms of “bulbs”: bulbs, true bulbs, tubers and rhizomes. These are essentially underground food storage units. Harvesting energy from their leaves during their active growing period, which is then stored once the foliage and flowers have faded, ready to be used again when conditions are right.

Although many bulbs are undeterred by cold climates, some species such as dahlias and cannas are native to warm, tropical climates and are therefore likely to perish if the soil drops below certain temperatures. In addition to this, all bulbs hate spending long periods in waterlogged conditions, because the basal plate (which produces roots) and layered scales (where energy is stored) are susceptible to fungal infections and to rot. If mold takes hold, very little can be done to save the plant and the bulb must be discarded.

Many cool climate gardeners and horticultural experts recommend removing tender bulbs from the soil and storing them in a cool, dry place over the winter.

Which bulbs are tender and need to be overwintered?

Gladioli, tender bulbs for the winter

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There’s no hard and fast rule as to which bulbs are tender, but there are a few likely contenders.

“Tender bulbs depend on the zone you live in,” says horticulturist Peggy Anne Montgomery. “In general, tender bulbs refer to plants that are only hardy in the warmer climates of zones 8 to 10. If you have the proper conditions, time and space to dig them up, they can pass the winter indoors, giving you larger bulbs for planning for the following season. If you don’t, it doesn’t matter. You don’t need to live without these beautiful flowers; you can plant them as annuals.

Many summer-flowering favorites are considered tender. “These include the ever-popular and spectacular dahlias, gladioli, begonias, canna lilies, caladiums, elephant ears and calla lilies,” says master gardener Tabar Gifford.

“These bulbs are planted in spring and typically reach full size and produce flowers in just one season.” Some are prized for their foliage, like elephant ears and caladiums (bonus points for canna which has both striking foliage and colorful flowers), while others are prized for their cheerful, vibrant blooms long flowering.

When is the best time to lift tender bulbs?

Dahlia Tubers, How to Overwinter Tender Bulbs

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Knowing when to lift tender bulbs is essential if you want them to survive the winter. “As tender bulbs are very sensitive to colder temperatures, it is very important to dig them up before the ground freezes,” says plant expert Katie Sunderlage.

“In general, a light frost will not damage the soil-protected bulb, but it may damage foliage or flowers that remain from the season.”

Wait until the foliage has died back naturally or at the first signs of frost. “If your bulbs are still plump and not mushy or rotten, you can prepare them to store for the winter,” advises Tabar. “You want to cut the foliage a few inches above the ground and then gently lift it out of the ground.”

How to Prepare Tender Bulbs Ready for Storage

Cleaning Bulbs, How to Overwinter Tender Bulbs

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A tried-and-true technique, Peggy Anne suggests: “Wash or brush all the soil off the bulbs and tubers and leave them to ripen in a dark, warm, well-ventilated place for about a week.” Glads and calla lilies can cure for up to three weeks. She also adds, “I find canna lilies to be the easiest to overwinter. After the first light frosts, I dig them up, I brush the ground; a little leftover on the tuber is okay, and let them cure for only two days.

If dry, sunny weather is forecast, you may want to leave the bulbs lifted and dry in the sun, as Katie Sunderlage suggests. “Prepare a location outside to allow the bulbs to dry in the sun for a few days. It is important to choose a few consecutive days without the risk of precipitation to be sure they dry well. Any moisture can cause the bulbs to rot during storage.

The Best Way to Store Tender Bulbs Over Winter

How to overwinter tender bulbs, gladiolus bulbs, store gladiolus bulbs

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Good ventilation is a crucial factor when storing flower bulbs. “Pack them in a breathable container then store them in a cool, dry place. Often, wrapping with wood chips or peat moss helps regulate humidity, so your bulbs don’t rot in storage or dry out completely,” says Peggy Anne.

The idea is to keep the bulbs in a dormant state until warmer, brighter days return, which will encourage them to regrow. Ensuring the right conditions is very important and Katie advises to “store in a dark, low humidity place where temperatures will not freeze but will not exceed 60 F.”

Once you have safely packed away the dormant bulbs, it is a good idea to check them from time to time. “A lot of people use crates or boxes with air holes,” says Tabar. “I would also add to watch out for creatures seeking out winter nesting sites.

“I stored my dahlias in the garage for a year after carefully digging them, cleaning them, drying them, and wrapping them in a mixture of wood chips and shredded newspaper. I was surprised to find that the winter storage I created quickly became a nesting place for field mice. My dahlias did not survive that year,” adds Tabar.

Try Amazon’s selection of collapsible storage crates or, for smaller quantities, opt for their hanging mesh storage bags.

Peggy-Anne Montgomery

Peggy Anne Montgomery is a horticultural professional with more than 30 years of experience in the United States and abroad in garden marketing and communications. An account executive for the Garden Media Group, she currently represents Dutch Royal Anthos, a trade organization for Dutch bulb growers and exporters in the United States and Canada.

Tabar Gifford

As the Customer Experience and Partnerships Cultivator at American Meadows, Tabar Gifford is a master gardener and dedicated “plant geek.” With a lifelong passion for gardening and nature, as well as a background in environmental studies and sustainable community development, she combines horticultural expertise with a commitment to education. Striving to empower individuals to achieve their gardening aspirations, Tabar embodies a true passion for sharing his knowledge.

FAQs

Do you need to overwinter tender bulbs planted in pots outside?

If you grew your tender bulbs in pots, you can follow the same practices to overwinter your bulbs planted directly in the ground. Cut the foliage, gently remove it from the ground, clean and dry, then package carefully for overwintering. “However, many gardeners also have success by simply moving the containers to a cool but dry place to store them,” says master gardener Tabar Gifford. “A garage, basement or garden shed can serve as a safe and sufficiently protected place from the elements to overwinter your tender bulbs in their containers. »

There is one caveat, though: “It’s always important to make sure they’re not too wet and that they’re in a healthy, viable condition,” says Tabar. “Another method used is to wrap your containers in frost blankets or wrap them with leaves to provide additional insulation for their winter naps. It’s important to keep in mind that containers will freeze before the ground, so if you have tender bulbs in the containers and in the ground, prioritize tending to the containers first when frost threatens.

Are oriental lilies considered tender?

Flamboyant and very fragrant bulbs, Oriental lilies are very popular in borders and in containers. Acid-loving bulbs, they thrive in sunny locations but are not as delicate as their flowers may suggest. “The general rule that bulbs planted in spring are tender has one exception: lilies. Oriental lilies are not tender and are just as happy to be planted in the fall as they are in the spring,” says master gardener Tabar Gifford. “For this reason, they are not tender bulbs and will happily overwinter in cold locations.” Most oriental lilies are cold hardy in zones 3 through 9.’

Inspired to continue enriching your flower bulb display, then discover how to transform a dull, shady spot with the best bulbs for shade and our favorite high-impact varieties for a spectacular show next season.