With the autumnal colors signalling fall’s arrival, the first frosts of winter are on the horizon. This means that, depending on your location, it is nearly time to bring less-hardy specimens undercover to protect them from plummeting temperatures.

Some tender plants, like tuberous begonias and evergreen agapanthus, need lifting and storing before the temperatures fall, but cannas and dahlias should wait until after the first frost. Having grown countless tender plants in the gardens I have managed over my horticultural career, including dahlias commercially, I explain why they should be lifted after the first freeze and tips on doing so.

With winter around the corner, now’s also the time to start thinking about your winter gardening checklist and insulate any outside faucets and clay pots against freezing temperatures. Suitable for protecting outside spigots and water barrel taps, you can purchase outdoor faucet covers from Amazon.

With cannas and dahlias originating from the American tropics and Mexico and Central America, respectively, it should come as no surprise that they prefer warmer climates and struggle in the cold.

Cannas and dahlias are tender perennials and will not survive if their rhizomes and tubers freeze, which damages their cell structure. This generally means that in USDA hardiness zones 7 or 8 and above, they can be mulched and left in the ground to flower the following year, just as long as the soil is not overly wet.

But in colder areas, you will need to dig them up and overwinter them somewhere cool, dark and frost-free.

When to Lift Cannas and Dahlias

Unlike salvias, pelargoniums, and citrus plants that need to be overwintered indoors or in a greenhouse before temperatures drop, canna and dahlia plants should stay outside until the first light frost has passed. This is because cold temperatures signal the end of the growing season and that the plant should enter dormancy.

However, it is important to wait until your canna or dahlia foliage has changed color or died back, as this indicates that the last of the plant’s energy has been transferred to the rhizome or tuber, ready for next year.

That being said, you will want to keep an eye on the forecast, as you will need to dig up your cannas and dahlias before any hard frosts or when the ground freezes, as this will most likely damage the rhizomes or tubers and cause them to decay in storage.

Once the foliage has changed color and died back, you can cut back the stem to around 6 inches above soil level, using a clean and sharp pair of secateurs, like these Okatsune 103 Bypass Pruners, available from Amazon. However, for thicker stems that are too big for cutting back with hand pruners, you may want to choose a pair of loppers.

The rhizomes and tubers of more established plants can spread surprisingly far, so start by digging around the plant, using a sharp spade, 12-16 inches away from the stems to avoid damaging the tubers. You can then lever the plant up and carefully lift it onto a tarpaulin or wheelbarrow.

Once lifted, you can brush away any soil clinging to the rhizomes or tubers, which will help prevent rot and make visual inspections later in the winter easier. Healthy rhizomes and tubers should feel firm to the touch. If you spot any soft or squishy areas, this generally indicates rot and these parts should be cut away using a sharp and sanitized knife, like this Linsen pruning knife, available from Amazon, before storing.

You will want to ensure that the skins are dry before storing your cannas and dahlias, as this will also help prevent them from decaying. You can do this by laying them out somewhere warm on a sheet of newspaper or a potting bench (available from Lowe's), out of direct sunlight for about a week.

However, if you grow dahlias and cannas in pots, you do not necessarily have to dig them up. Instead, you can cut them back after the foliage dies back and move the pots to cool, but frost-free position, like an unheated greenhouse or garage.

If the temperature in your storage area looks like it will fall below freezing, you can protect your pots with bubble wrap or blankets to help insulate them.

To ensure viability, you will want to store your cannas and dahlias somewhere cool, dry, and dark. A temperature around 45°F to 55°F will keep the plants dormant, but avoid spots where temperatures may drop toward freezing, as this can damage them.

You can store your cannas and dahlias in boxes filled with a medium such as dry soil, sawdust, or vermiculite, or wrap them individually in newspaper or hessian sack. Wooden boxes, such as pine crates available from Lowe’s, or milk crates from The Home Depot, make great options because they encourage airflow. However, to prevent the tubers from sweating and decaying, avoid airtight containers and sealed plastic bags.

If storing in a box, start by adding a layer of sawdust or vermiculite, available from Amazon, to the bottom and place the rhizomes on top with space between them so that they do not touch. Once that layer is compete, you can continue adding layers until the box is full.

Unfortunately, mold can spread rapidly, especially when tubers are in close proximity, so it is advisable to check any stored cannas and dahlias every few weeks whilst they are in storage. If you spot any white or grey mold, you can clean them with a vinegar solution, but any soft tubers should be discarded.

One key lesson I have learned over the years is to think ahead about how you will label your stored plants, as there is little way to tell their variety or color when you come to plant them next year.

If you are storing large numbers of the same cultivar, you can label boxes and crates with stickers and waterproof markers, but for individual specimens I recommend wrap-around plant labels, available from Amazon, that you can tie to each plant’s rhizome or tuber.

What to Shop

If you've stored your cherished dahlias or cannas away until next year, you might be wondering how to add a bit of color to your patio or porch and brighten it up over the coming winter.

From winter pansies and violas to cyclamen and hellebores, with the right planning, you can have a selection of winter container flowers that will provide a succession of interest through the colder months.

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