Gardening Sweet Spots
By Donna Hessel
Overwintering Containers in a Garage
I can only grow perennials in containers in my small garden, and I don’t want to replace them every year. Following tips provided by Kerry Meyer in one of her lectures for Proven Winners, I was successful in overwintering my container plants in the garage. My plants included painted ferns, several hosta varieties, variegated iris, hydrangea, brunnera and dracaena. My gryphon begonia moved indoors to be a houseplant over winter. There are many other perennials that can be saved as well.
To overwinter containers in the garage, they should be left in the garden as long as possible but brought inside before a hard frost. The plant foliage will begin to die off as the weather gets colder. Containers should be watered thoroughly and drained before bringing them indoors. Pots should be placed next to an indoor wall if possible and huddled close together on the ground. If the garage floor gets very cold, placing them on cardboard or foam core board will add extra insulation. In an unattached garage, or if it is an exceptionally cold winter, wrapping a layer of bubble wrap around the group can provide extra insulation. The space can be either dark or with some light. Large containers offer more protection to the roots than smaller pots. The soil will freeze but will be protected from freeze-thaw cycles. Ideal temperature is between 20-45 degrees F.
Plants will eventually die back to the ground and the dead foliage can be cut off. Adding some straw or other mulch to the tops of the pots can be beneficial. I added a layer of pine straw to my pots, which also helps to maintain moisture when they are outside in the summer heat. Kerry recommends covering the containers with a white sheet (not plastic because air cannot penetrate it) and not watering the containers at all until new growth starts to show in the spring. I did not cover my containers and I did not water them. When warmer spring temperatures arrive, the frozen soil will thaw and moisten the roots. When active grown begins – usually April in our area – plants will need to be watered and fertilized until after the last frost (usually mid-May) and it is warm enough to move the containers back to the garden.
Other Options for Overwintering Containers
Place in gardens or on a patio: Some plants are hardier than others. The general rule for a plant to be winter hardy is that it should be two zones hardier than the climate zone you are in. In this area (zone 6), that means plants should be hardy to zone 4. The soil in a pot freezes harder than that in the larger mass of soil in a garden and will also thaw more quickly, leading to multiple freeze-thaw cycles that are hard on plants. If you want to try overwintering containers in a garden or on a patio, plant in containers that won’t break from the freeze/thaw action and group them together. Good container choices are plastic, composites, metal and wood. The soil should not completely dry out and containers need to be able to drain. Adding pot feet will allow pots to drain. I find that the tops of peanut butter or mayonnaise jars placed under the pots provide adequate clearance for drainage. Adding mulch to the pots will help to insulate the roots.
Dig into the garden: Pots with the plants intact can be placed in holes dug in an empty spot in the garden. The lip of the pot should be either slightly above or level with the ground. Soil must be packed around the pot. It probably will not need to be watered. In the spring, the pot should be pulled out of the ground, repositioned in the garden and fertilized.
Transplant into the garden: In the fall, perennials in containers can be transplanted into soil to overwinter in the garden. In the spring, they can be dug up and put back into a container or left to grow in the garden.
Overwinter in trenches: Plants can be kept in their pots and overwintered in trenches. The pots should be tipped over into the trench and covered with soil or mulch to protect them. Come spring, pots are simply uncovered, set upright, cleaned up as necessary, repositioned in the garden and fertilized.
Enjoy them as houseplants: For several years I have brought the gryphon begonia inside to live as a houseplant during the winter season. The foliage slowly dies off and by March not much is left except some stems. I water it just occasionally and in April I add fertilizer when new shoots start to appear on the bare stems. Rex begonias can also become houseplants in the winter. All begonias need to move indoors before the first frost.
After the last frost (usually after mid-May in our area), containers can be replaced in the garden to be enjoyed for another summer season. The addition of some fresh soil will promote fresh growth and a water-soluble fertilizer applied every 10 days or so will help them thrive and bloom.
Text Reference: Proven Winners.com-Container Plants – “Overwintering Pretty Perennials and Shrubs, Contributor: Kerry Meyer
Photos: gardenlady.com-plants in garage, plants in garage – Preen , pexels-28879443 crop
