As tropical foliage plants, species of Coleus aren’t the best at dealing with cold temperatures.
But with a bit of preparation ahead of time, they can survive the chilly temperatures of winter year after year.
Hardy in USDA Zones 10 to 11, coleus sports foliage with delightfully bright, vivid colors.
They are varied, too – you can find coleus cultivars in pretty much every pattern and color you can think of, save for true blue.
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As pretty as they are, these tender leaves don’t do so well when it’s cold out, so gardeners in northern climates often opt to grow them as annuals, relegating them to the compost pile at the end of the season and purchasing new specimens or starting seeds come spring.
But with a bit of prep ahead of winter, you can keep your coleus alive over the cold months and save you having to start again come spring!
In our guide to growing coleus, we cover how to cultivate these delightful perennials in your landscape.
This guide offers different ways of winterizing coleus, to ensure you can enjoy the plants for more than one growing season. Plus, we’ll go over how to deal with any cold damage if it occurs.
Here’s what we’ll be discussing:
Coleus and the Cold
As mentioned earlier, coleus needs to be in USDA Hardiness Zones 10 to 11 to grow outdoors as perennials full-time.
They’ll grow as annuals in other Zones, dying back in winter or when exposed to extreme heat.
It’s the cold that we’re focusing on, and in Zone 10, temperatures can drop to as low as 30°F. In temperatures below 40°F, the foliage will wither, turn dark, and eventually die.
But even more moderate temperatures in the 40s and 50s can do some damage, such as stunting their growth and causing leaf drop.
Plus, the plants will just droop and look kinda sad, which isn’t ideal.
Therefore, to keep your specimens at optimum levels of health and aesthetics, 60°F is the threshold that you should remember and focus on.
Whenever temperatures start dropping below this temperature, you should take some cold-protective action ASAP.
“But which actions should I take?” I’m glad you asked…
Winter Protection
If your coleus are at risk of being exposed to temperatures below 60°F, the following methods can help shield them from the harmful effects of the cold:
Cover and Insulate
This is perfect for those short-lived temperature dips that don’t warrant a full-on move indoors.
When you place frost cloth around a plant, it helps retain some of the heat from the air and from the soil as it rises. As the heat is trapped, it has no choice but to warm up your coleus!
By loosely draping some frost cloth over and around your plants, you can add up to 10°F of ambient heat to your specimens, depending on the type and thickness of cloth that you use.
Cover the specimens snugly, but not tightly – you’re not trying to shrink-wrap your plants here.
Don’t cinch the cloth around the bases, either. Instead, arrange it like a teepee over your specimens, as a wider base will help to capture more heat.
Planket Frost Protection Blanket
For a lightweight, durable, and breathable frost protection cover that’s available in a variety of different dimensions, you can purchase the cleverly-named Planket over at Amazon.
Overwinter Indoors
So you’ve looked at the forecast, and the 60-degree temperatures at night are pretty much over until next spring.
Sheltering your coleus indoors during the cold weather is an effective strategy. Plus, you get to liven up your digs with some lovely new houseplants!
If you’ve got your coleus plants growing in containers, then those can be brought indoors, easy-peasy.
Just put them under some grow lights or near a sunny window, and make sure the indoor temperatures are somewhere between 60 to 75°F.
If you want to save your in-ground ones, then those should first be moved into containers filled with a 50:50 mix of peat moss and perlite, or some other moisture-retentive yet well-draining potting medium.
Make sure the containers have drainage holes at the bottom, and that they’re about an inch or two wider than the roots. Carefully dig up the plants and pot them up into the containers.
Before they can come inside, you should check your plants for pests and disease.
Piercing-sucking pests like aphids and spider mites can be wiped off with a soapy cloth or sprayed with neem oil, while any coleus plants with symptoms of disease should not be brought indoors, as they could spread infection to your other houseplants.
While they are indoors, keep the growing medium evenly moist, and set the container onto saucers to catch excess water trickling out of the bottom of the pot.
Once nighttime temperatures are consistently above 60°F, then you should be good to bring your container plants back outside. But make sure to gradually harden them off first!
To do so, leave them outside for 30 to 60 minutes before bringing them back inside. Each subsequent day, add an additional half to full hour of outdoor exposure until the plants can handle a full day’s worth.
Propagate Cuttings
If you have coleus plants that you’re growing as annuals and you don’t want to bring them indoors over the winter months, you can propagate new plants via stem cuttings instead.
New plants propagated from stem cuttings will be perfect genetic copies of your beloved coleus, with the vigor of youth to grow like a weed come spring.
This method is also perfect for prolonging specimens that have taken a beating but are of good stock, like a prized cultivar with a lot of chewed-up leaves from pests.
Start by removing three- to four-inch stem cuttings from the tips of healthy-looking shoots.
Defoliate the bottom half of each cutting, and dip the cut ends into a rooting hormone such as this IBA rooting powder from Bonide, available at Arbico Organics.
Bonide Rooting Hormone Powder
Then, stick the cuttings into a container filled with a well-draining, yet moisture-retaining medium such as a 50:50 mix of peat moss and perlite.
A six-inch container has enough room for a dozen stem cuttings, but if you want to give each cutting its own container, individual two- or three-inch pots work, too.
Gently water the potting media then cover each container with a clear plastic bag, propped up so it doesn’t interfere with the stem cuttings. Place the containers in a bright spot indoors where temperatures are between 60 and 75°F.
After rooting, which usually takes about seven to 10 days, each cutting should go into its own uncovered container, if they aren’t already.
Keep the media moist throughout their indoor stay, and repot the cuttings whenever their current containers become too cramped. Shoot for a pot that’s at least an inch wider in circumference than the root system of the plants.
Keep an eye on the temperature outside – once nighttime lows are regularly above 60°F, you can harden off the cuttings outside with the same protocol described above.
Then, you can plant them in the ground or in swanky outdoor containers!
Treating Cold Damage
If your coleus has browned, blackened, and/or wilted leaves, you’ll need to prune those off, but timing is important here, you don’t want to prune until the cold temperatures have passed.
During the cold spell, these damaged leaves and stems can offer a bit of protection to the remaining healthy tissue, kinda how a scab can protect a wound.
If you prune too early, then you’ll run the risk that the rest of the plant will become damaged.
If your coleus suffers extensive cold damage, you may need to simply remove it and start again – check if there’s a healthy stem or two to use for propagation.
Cold Coleus? No Problem
Whether you decide to cover your plants or bring them indoors, you no longer have to worry about cold-damaged coleus. You can even take cuttings from those grown as annuals to replant in spring.
Any questions, concerns, or wisdom of your own to share? Let us know in the comments section below:
And for more information about coleus and other foliage plants, check out these guides next:
