The weather has shifted to fall, but if the long-range forecast can be trusted, we have some time before frost and freezing temperatures change the landscape.
The cooler nights will take a toll on tender plants, so take this opportunity to harvest cuttings from some of your favorite annuals. Many will grow well under lights or near a bright window and can be kept as a houseplant through the winter. These plants can also be multiplied over the months, providing you with new plants to put back into the garden next spring.
Coleus is an excellent candidate for this. You’ve probably noticed that the fancy varieties are almost always sold in 4-inch pots, and usually cost $3 to $5 each — another great reason to keep some of your favorites going for more than one season.
Choose a branch without flowers, if possible, and cut a 4- to 6-inch section from the end. Roots will form on the stem where the leaves attach, so remove the lower few leaves from the cutting and place either in water or in a small pot of moistened potting mix. I prefer to start them in soil, since the water roots tend to be fragile, and the plants will need to be transplanted to soil eventually anyway.
New plants will root in a few weeks. Pinch off any flower buds that form, and as the plants grow taller, they may be trimmed to promote full, bushy growth. Wherever the stem is cut, two new branches will grow.
The cuttings from that trim can also be started as more plants; just make sure they are long enough for a couple of leaves to be removed from the cut end, with a few more remaining at the tip. Repeat the process through the winter to keep plant size manageable and create as many new plants as you like.
Sweet potato vines respond well to the identical treatment and are even more vigorous growers than coleus. It’s also worth noting that these are truly sweet potatoes — so another option is to wait until frost kills the vines, then dig for some tubers. These can be stored in a cool, dry, dark place as you would potatoes or ornamentals such as cannas and dahlias. You can replant the tubers in spring, or pot them up in midwinter, wait for new growth, then start taking cuttings.
Geraniums can also be kept this way. They are a bit slower to root and establish, and the cuttings should be allowed to cure or callous for a day or two before planting in soil.
I also like to treat the cut ends with a dusting of rooting compound, found in the houseplant fertilizer and supply section at the garden center or greenhouse — it’s not necessary, but it can help improve the success rate.
Do note that many of the fancy hybrid geraniums are patented, so your cutting-grown plants should be for personal use only, not to sell.
Coleus, sweet potato and geranium are tried and true, but you can try this method with just about any annual. Through trial and error, I’ve found the ones that work well for me; plants that handle the indoor conditions I have available and are forgiving of my neglectful care.
Resist the temptation to go overboard trying to save too much. Some plants are best replenished each spring, and you’ll want to tray some of the new varieties anyway.
But do choose to save from the frost and keep in your garden another season.