Yard and Garden: Over-wintering Tender Perennials

September 26, 2018, 11:26 am | Richard Jauron, Willy Klein

Dahlia hcast/stock.adobe.com.AMES, Iowa -- Perennials such as tuberous begonias, gladioli, cannas and dahlias are an integral part of many home landscapes. They put on excellent displays of color until a killing frost. Unfortunately, they will not survive our harsh winter weather outdoors and must be dug in the fall and stored indoors through the winter months. Horticulturists with Iowa State University Extension and Outreach share information about the cultural and winter storage requirements for several commonly grown tender perennials. 

How do I overwinter cannas?  

Cut back the plants to within 4 to 6 inches of the ground a few days after a hard, killing frost. Then carefully dig up the canna clumps with a spade or garden fork. Leave a small amount of soil around the cannas. Allow them to dry for several hours. Afterwards, place the cannas in large boxes, wire crates or in mesh bags. Store the cannas in a cool (40 to 50 degrees Fahrenheit), dry location.  

How do I overwinter dahlias?  

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 or seven days to “cure.” Then carefully dig up the dahlias with a spade or shovel. Gently shake off the soil, then cut the stems back to the crown. (The dahlia 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. Allow the dahlias to dry for 24 hours. Place a layer of vermiculite, peat moss or wood shavings in the bottom of a cardboard box. Lay the dahlia clumps in the cardboard box and cover them with additional vermiculite, peat moss or wood shavings. Store the dahlias in a cool (40 to 50 F), dry location.  

How do I overwinter gladiolus bulbs?  

Carefully dig up the plants with a spade in late summer/early fall. Gently shake off the soil from the bulb-like corms. Then cut off the foliage 1 to 2 inches above the corms. Dry the corms for two to three weeks in a warm, dry, well-ventilated location. When thoroughly dry, remove and discard the old, dried-up mother corms located at the base of the new corms. Remove the tiny corms (cormels) found around the base of the new corms. Save the small corms for propagation purposes or discard them. Place the corms in mesh bags or old nylon stockings and hang in a cool, dry, well-ventilated location. Storage temperatures should be 35 to 45 F.  

How do I overwinter tuberous begonias?  

Carefully dig up the tuberous begonias within a few days of a killing frost. Leave a small amount of soil around each tuber. Cut off the stems about 1 inch above the tubers. Place the tubers in a cool, dry area to cure for two to three weeks. After curing, shake off the remaining soil. Place a layer of peat moss, vermiculite or sawdust in a small cardboard box. Lay the tubers on the storage medium, then cover the tubers with additional peat, vermiculite or sawdust. Store the tubers in an area with a temperature of 40 to 50 F.  


Dahlia: photo credit hcast/stock.adobe.com

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