Minnesota & Seasons

Saving geraniums, dahlias and cannas over winter

The short answer: wait for the first frost to blacken the leaves, dig or bring them in within a week, and store them cool and nearly dry until spring. Geraniums can also live on a sunny windowsill as houseplants. Dahlias and cannas go into storage as dormant roots in a cool basement or garage that stays above freezing.

Geraniums: three ways to keep them

As a houseplant. Before the first hard frost, cut the plant back by about half, check the undersides of the leaves for bugs, and pot it up in fresh mix. Give it your sunniest window and water only when the soil is dry. It will get leggy by February; pinch it back and it will bush out again in spring. (Our guide to bringing plants inside has the pest check.)

As cuttings. Take 4–5″ tip cuttings, strip the lower leaves, let the ends dry for an hour, and stick them in moist potting mix. They root in about three weeks and take up far less room than the whole plant.

Bare-root and dormant. The old-timer method: pull the whole plant, shake off the soil, and hang it upside down (or set it in a paper bag) somewhere cool and dark, around 45–50°F. Once a month, soak the roots for a couple of hours if the stems look shriveled. In March, cut the stems back to live green tissue, pot them up, and set them in a sunny window. Not every plant makes it, but most do.

Dahlias: dig after frost, store in peat

Let the first frost blacken the foliage; that tells the tubers to go dormant. Within a week or so, cut the stems to about 4″, lift the clump carefully with a fork (the tuber necks snap easily), and hose off the soil. Let the clumps dry for a few days somewhere frost-free, stems pointing down so water drains out of the hollow stalks.

Pack them in a box or bin with barely damp peat moss, vermiculite or wood shavings, label each variety, and keep them at 40–50°F. Check once a month: if a tuber is shriveling, mist the packing lightly; if one is soft or moldy, cut the bad part away or toss it.

Cannas: dig and store the rhizomes

Same timing as dahlias. After frost, cut the stalks to 4–6″ and dig the clump. Cannas store best with some soil left on, so just knock off the loose dirt. Let them dry for a day or two, then store in a crate or cardboard box, loosely covered with peat or newspaper, at 40–50°F. They're tougher than dahlias and rarely need checking.

Waking them up in spring

In late March or April, pot dahlias and cannas into gallon pots in a warm, bright spot to get a head start, or plant them straight outside once the soil warms, usually late May in East Bethel. Don't rush them out. All three are warm-weather plants, and cold soil just makes them sit and sulk (see hardening off before they go outside).

Where to store them

The sweet spot is 40–50°F and dark: an unheated basement corner, a root cellar, or an attached garage that never drops below freezing. A heated living space is too warm and dry; the roots will sprout early or shrivel.