The autumn is not only harvest time — it’s also a good time to prepare your garden for next year. Part of that process involves digging up your tender tubers, corms, and bulbs to protect them from freezing temperatures and inclement weather. Even if you live in an area that doesn’t normally experience freezing temperatures but does see an increase in rainfall, it’s still a good idea to dig them up to ensure they don’t rot underground. So exactly when should you dig up your dahlias, gladiolus, and begonias, and what’s the best way to do so without damaging them?
Protect your tuberous plants like dahlias, tuberose, and tuberous begonias from the elements by digging them up after the first frost of the autumn. If you grow tuberous plants in pots, your job is easy: just bring the containers in the house and store them in a cool, dry area for the season. Many tuberous plants are touted to be hardy to zone 9 and will usually go dormant, turn yellow, and drop their leaves and greenery. Still, digging them up will prevent them from rotting in the ground over the winter.
Those who live in zones 8 and below will also want to dig their tubers up following the first frost of the fall. Although it’s best to wait a week or two after the frost, light frosts are often followed by hard ones, so that may not be possible. Once your area experiences a light frost, pay attention to the weather forecast. If a hard frost is expected, get them out of the ground to prevent potential damage.
When digging up your tubers, you'll want to be careful not to damage them. Use a pitchfork or spade to loosen the soil and begin digging in the dirt about a foot from the stem of each plant. Once the tubers are in sight, carefully pull them out of the ground and use your fingers to brush the dirt from them. If the leaves and stems have been damaged by frost, trim the affected bits, but leave the greenery if it’s fine.
Clean your tubers by filling a tub or sink with water, or simply shower them with the garden hose. In either case, be careful not to damage their skins. Take the time to inspect each tuber and trim away any areas of rot. Before you cut, sterilize your tools by heating their blades and letting them cool. Many gardeners also divide their tubers at this time, but this is a task that can wait until spring. Let the tubers dry for a few weeks in an area with great air circulation that’s out of direct sunlight. Once they’ve dried, remove their stems. Then, apply an antifungal powder like sulfur dust to them to prevent the spread of rot. Be sure to wear gloves, a face mask, and other protective gear when doing this.
To store your tubers, line a box with newspaper and fill it with peat moss, coarse sand, wood shavings, saw dust, or vermiculite. You’ll want to label the tubers so you know exactly what you’re planting next year. Write on the tubers themselves, or place them in paper bags/wrap them in newspaper and label that instead. Spritz your storage medium with water to prevent the tubers from drying out, and place them in the box.
Over the winter, you’ll want to periodically inspect your tubers and throw away any that are rotted or mushy. If you find that they're drying out, spritz the storage medium again.
Corms, such as gladiolus and freesia, should also be dug up after the first frost. However, you can also choose to dig them up once they're done flowering and their foliage has turned brown, as long as it’s within the eight-week period before your area typically gets its first frost of the year.
The process for digging up corms in the fall is similar to that of digging up tubers. Using a pitchfork or spade, start digging about a foot away from each corm. Gently pull them up and carefully remove the dirt from them. Unlike tubers, you can let the corms "cure" by placing them on top of the soil to dry for a few days. However, if rain or frost is in the forecast, dry them in an indoor area with good air circulation instead.
Once the corms are dry, separate the old ones from the new ones with cormlets on them. Many gardeners throw away the old corms. Remove dead foliage and brush away any excess dirt. Throw away any corms that are soft or beginning to rot, and dust the remaining corms with an antifungal powder. Layer them in a box, placing newspaper between each layer. You can also hang them in a breathable produce bag or even nylon pantyhose. Place the box or hang the bag in a cool, dry area that stays around 40 degrees Fahrenheit, such as the garage or in the refrigerator's vegetable bin.
Spring-planted bulbs can be dug up once their foliage turns brown and they go into dormancy or when the first frost occurs, whichever happens first. If you’re not sure, try tugging at the brown foliage. If it breaks off easily, the bulb is probably dormant.
Again, dig about a foot away from each bulb using a spade or trowel. Dig under the bulbs and lift them from the ground. Once you’ve pulled up the bulbs, brush the dirt off of them and look for signs of damage or rot. If a bulb has soft spots, signs of rot, or has otherwise been damaged, throw it away. This is also a great time to divide your bulbs and twist them free of one another.
Dry your bulbs for about a week, and remove any remaining foliage from them. Dust them with an antifungal powder, place them in paper bags, and put the bags in a box filled with peat moss, vermiculite, or another storage medium. Store the box in a cool, dry place where the temperature remains between 60 and 65 degrees Fahrenheit.
Remember that no matter how much care you give your tubers, corms, and bulbs when you dig them up and store them for the winter, it’s normal to lose a few in the process. Check on them over the winter months, looking for rot and throwing away any that show signs of disease. With a little bit of care, you’ll be able to put some perfectly healthy plants in the ground come springtime.