After pampering garden plants throughout the growing season, it is difficult to watch them die from that first hard frost. Although the Colorado Springs area did endure frigid weather this month, that light frost likely wasn’t enough to do damage to most of our tender perennials. If yours survived, they can be over-wintered with proper care for use next year.
Bring your vigorous, healthy, and insect and disease-free geraniums indoors before the first hard frost. Repotting them in fresh potting soil will minimize the risk of insects.
For plants in larger pots or in the ground, carefully dig up the geranium and plant in a 6– 8-inch pot with potting soil. Prune back each plant by one-half, cutting the stems just above a leaf. Ideally, geraniums need at least 10 to 12 hours of light indoors, so place the plants in a bright south window or under fluorescent lights.
Insufficient light will result in weak growth and poor flower production during the winter. If you don’t have a brightly lit location, keeping them cool will slow their growth and reduce the need for bright light. Temperatures of 65-70 degrees during the day and 55-60 degrees at night are recommended.
Carefully dig up the tuberous begonias within a few days of a killing frost, leaving a small amount of soil around each tuber. Cut off stems about 1 inch above the tubers, and place them in a cool, dry area to cure for two or three weeks.
After curing, shake off the remaining soil and lay the tubers on a layer of peat moss, vermiculite, or sawdust in a small cardboard box. Then cover the tubers with additional peat, vermiculite, or sawdust. Store them in an area with a temperature of 40-50 degrees. Do not allow them to freeze.
Cut back the plants to within 2 to 4 inches of the ground three or four days after a killing frost. After cutting back the plants, leave the dahlias in the ground for an additional six to seven days to “cure.” Then carefully dig up the dahlias, gently shaking off any soil, and cut the stems back to the crown. (The crown is located at the base of the stem where the tuberous roots are attached.)
Carefully wash the dahlia clumps to remove any remaining soil and allow them to dry for 24 hours. Lay the dahlia clumps in a cardboard box with a layer of vermiculite, peat moss or wood shavings, and cover them with additional vermiculite, peat moss or wood shavings. Store the dahlias in a dry location at 40-50 degrees.
Bring these plants indoors before the first frost. Then the secret to overwintering succulents not hardy to USDA zone 5 is to greatly limit the frequency of watering. Many will actually rot if they’re kept too wet, so only water them every six or eight weeks, being careful to keep the foliage dry.
El Paso County Extension is operating remotely due to COVID-19. Submit gardening questions by email at firstname.lastname@example.org.