One of the best ways to grow food sustainably is to use perennial plants as they can survive for several years in their native environment. However, not all perennial plants are able to survive winters in Canada – some are ‘tender perennials’ rather than ‘hardy perennials’. As a result, gardeners need to move some of these tender plants indoors to survive the winter and then replant them outdoors in spring, once conditions are favourable. Some of the plants that I typically move indoors include peppers, pineapple sage, rosemary, and hibiscus.
To successfully move a plant indoors, you need to consider the short-term and long-term needs of the plant. Once indoors, the plants’ short-term needs include the necessities of life: water, CO2, light energy, nutrients, and a livable temperature. These are generally known quantities and are all available indoors, although you may need to use a supplemental light source.
You also need to look forward to next year’s plant growth. Specifically, if the plant actively grows indoors over the winter, it will get leggy and weak due to different growing conditions and limited energy from the sun. It may also attempt to flower or bear fruit, which is unlikely to succeed in an indoor environment and represents wasted energy by the plant. To limit any unhealthy and unwanted growth, we must put the plant into a sort of stasis.
So how do we achieve this? Here are the steps for moving your tender perennials indoors for the winter:
The first step is to carefully dig up the outdoor plant. Allow plenty of margin around the roots – you don’t want to sever them as this will shock the plant.
The second step is to wash the plant. Carefully spray the soil off the roots, and then hold the bare-root plant upside down and spray the undersides of the leaves to remove potential pests – pests may live in the soil or on leaf undersides in egg or larval form. If you see any signs of pests/eggs after spraying, wipe them away with a soap-and-water mixture or with neem oil.
Next, transplant your new houseplant into indoor (i.e., sterile) potting mix in an appropriate-sized pot. The pot should be the smallest size needed to fit the roots and support the plant. Avoid using large pots that provide room for growth as you want the plant in stasis mode when it’s indoors. Spread the roots out within the pot to avoid root tangling, and root prune only if required. Make sure you press the potting mix down around the roots to push out air pockets and to properly support the plant. If the plant was already in a container and you are using the same pot that was outdoors, scrub it with soap and water.
Once the plant is in its pot, you may need to prune it to a smaller form if it has a lot of foliage. While the foliage enables photosynthesis, it can lead to water loss and make the plant leggy, so prune it back by about 50% to limit these issues.
As with any recently transplanted plant, ensure that the soil stays slightly damp (never sopping wet) for the first two weeks until the roots establish. Put it in the brightest place possible, such as beside a south-facing window or beneath grow lights.
The plant will likely have transplant shock and may shed many of its larger leaves – this is not your fault and is not a problem. While it’s unnerving to watch the leaves turn yellow, this is due to the plant being moved to a new growing environment and the plant won’t die if you water it correctly.
After its two-week orientation period, water and fertilize minimally thereafter to restrict growth. This is where your goal of pushing the plant into dormancy comes into play. Water the plant sparingly through the winter, ensuring that the soil dries between watering. Do not add fertilizer until a few weeks before you transplant it back outdoors. Also, watch for any pests that may have tagged along – you may need to use a soap-and-water spray and/or a hand vacuum to deal with any pest infestations.
Keep the plant alive and healthy but not more than that until you are preparing to transplant it next year. Once you return the established plant outdoors in the spring, you’ll be rewarded with a much higher yield than if you merely planted from seed!
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