I almost missed the window to overwinter my ornamental sweet potato vines. Luckily, so far in the Chicago region the temperature only hit a low of 35 degrees Fahrenheit. As you can see in Photo 1, the vines were only slightly damaged by this minor frost. In case you are curious as to the definition of a frost, the Illinois State Water Survey State Climatologist uses a temperature threshold of 32° for frost and 28° for a hard freeze.
When bringing my sweet potato vines inside for the winter I take a different approach. Typically, in my container gardens the vines do not develop much of an underground tuber (fleshy root) shown in Photo 2. So, I choose to overwinter my sweet potato vines as houseplants. I find bringing the bright chartreuse green and deep purple foliage into my home creates excellent houseplant color.
Most sources suggest treating sweet potato vines as dormant bulbs, but I have not had great success with storing my puny tubers in peat in a cool place. They tend to dry out, shrivel up and die. To learn more about common overwintering practices for tender plants click here.
These are the steps I use to overwinter my sweet potato vines as houseplants:
I cut back the top of the vine and leave about four to six inches of healthy foliage (Photo 3). I dig up the roots and tuber being careful not to slice the fleshy part (Photo 4). Then I inspect the plant closely for insects, such as spider mites, aphids and whiteflies. If I spot these insects, I choose not to overwinter the plant and simply caulk it up as a loss. However, there are effective insecticidal soaps that are safe for indoor use. To learn more about these products click here.
If I see no sign of insects, I pot up the vine in a professional growers mix (Photo 5). As mentioned in a previous post, be sure to pre-mix the soil-less growers mix (peat-based product), so water adheres to the peat particles (Photo 6). I only put one vine per pot to allow room to grow and provide good air circulation (Photo 7). Then the pots are placed in a sunny window (west or south side of my home).
Next spring, I will slowly bring out my vines during the day and bring them in at night over a two-week period. This helps acclimate them to the outdoor climate. Once danger of frost has passed, I will transplant them into containers and fertilize. Sometimes they are slow to start, but they will catch up to my other annuals quickly.
There is a bit of work involved in overwintering plants, but this saves me quite a few dollars next spring.Stay tuned for my next post on overwintering dormant bulbs, such as cannas and elephant ears. These are a bit pricier at the garden centers and somewhat easier to store over winter.