If you have a few favorite pepper plants that you'll be sad to see go once winter arrives, overwintering them can provide a way to enjoy your plants for another year. Sometimes, several years. Peppers are perennials, so it's not difficult to do – even with limited room.
Second year pepper plants are usually highly productive. In spring when moved back outside, they'll usually send off many new branches turning the plants into more of a bush, creating higher fruit density for many varieties. Additionally, since they have a head start over seedlings, they'll flower and produce fruit earlier in the year.
If your experience is similar to ours, aphids will be a factor when winterizing pepper plants. Aphids tend to favor our overwintered plants over seedlings and pepper starts. By being vigilant, we've been able to reduce – but, not eliminate – their impact. More on dealing with aphids follows below, though, it's key to start the process by selecting only healthy plants for overwintering. Specifically, avoid plants infected with the Mosaic virus, which can be transmitted to nearby plants via pests – such as aphids.
Most pepper plants are usually productive until the first freeze. A hard freeze will kill the plants. During autumn, keep a close eye on the forecast, watching the evening low temperatures. Prior to the first freeze, you'll want to start the process of winterizing your peppers.
When wintering, we cut the plants back considerably to help them become more dormant so they can save their energy for the next year. Once indoors, the plants will tend to lose their leaves anyway, which makes a mess. We'll take away 95% or more of their leaves, leaving only a few. We also trim the plant's branches back quite significantly, reducing it to less than one-third of its original size.
To save space and bring more plants inside, we'll also take many of the plants out of their original pots (or out of the garden) and re-pot into much smaller 4" pots (8" for large plants). We'll cut the roots back to make it fit and will prune the plant drastically – usually to around 6-8 inches of the main stem(s) and some may not have any leaves. It looks extreme to remove that much; however, we typically only lose 10-30% of the winterized plants that were downsized to this extent. Water after transplanting to help them recover.
Next we spray the plants with insecticidal soap and continue to keep them outdoors for a couple days to kill off and disperse aphids and other pests. It can be bought at a garden supply store, or you can easily make your own (see below). We've used both and had similar results.
When wintering, keep the plants in a sunny window and water when dry. Within a couple of weeks, you'll see new leaves appearing on the stems. If it weren't for aphids, caring for wintered pepper plants would be extremely easy.
Once the new growth sites emerge, the aphids will usually show up around those – especially toward the very tips of the new branches, near the newest growth. Our first line of defense is to apply insecticidal soap at the first sign of the pests. Monitor the outbreak. Limit application of the insecticidal soap to once every few days, and only apply as needed.
Here in Georgia, we'll get a number of 60°F plus days in winter. We store our 4" winterized plants together in plastic bins so we can easily bring them outside on nicer days. As long as the temperature stays above, or near, 40°F at night and 50°F during the day, we'll continue to leave them outside. Doing this helps reduce aphid/pest populations as it exposes them to cooler temperatures and natural predators. In colder climates, moving the plants to the garage for a few days (if above freezing) can also help.
Alternating between the insecticidal soap and periodic preventive exposure to cooler temperatures is usually enough keep your winterized plants in relatively good shape. If the aphid population starts growing, we're more aggressive with exposing the plants to colder temperatures, and for longer periods. When outside, we'll also spray with the soap solution to give the vermin a double-whammy.
If aphids get the upper hand and do significant damage, you'll first want to take above steps to remove the population as much as possible. When the damaged plants are pest-free and brought back to indoor temperatures, we've found they'll usually recover.
All that said – with winterized peppers – monitoring the new growth is important. If dominated by curled/malformed leaves with yellow spots, it's likely the plant has the Mosaic virus. If you suspect a winterized plant has it, it's best to quickly remove and dispose of it (and its soil) to reduce the chances of the virus being passed to other plants.
We've tried the yellow sticky insect traps to target aphids and other flying pests. In our use, we've found the traps to be more effective at trapping Aphidius colemani and Aphidius ervi – tiny parasitic wasps that kill aphids (harmless to humans) – than the targeted adult aphid flies. Apparently, as the aphids are (somehow) hitching a ride into our dwelling, their hunters aren't far behind. As such, we believe these traps are likely counterproductive.
We're currently trying to induce near-dormancy in wintered pepper plants by keeping them outdoors (or in a garage), for everything but the most extreme conditions. We've kept the plants in their original containers to minimize transplanting stress, while cutting the plants back to the main stems – removing nearly all leaves. Nearly all winter, we've kept them outdoors – only bringing inside during periods of prolonged freezing temperatures. This has helped to keep new growth to a minimum and we've witnessed only mild aphid activity. This spring, we'll see how these plants recover.
To minimize sun scalding when first bringing plants outside for the spring, it's best to keep them out of direct sunlight for the first week, then gradually moving them to increasingly more direct and longer sun exposure. If they do end up with scalding – leaves will turn whitish and wilty, then drop off after a couple of days – don't worry, they'll usually start growing new leaves within a week or two. Just make sure to keep them watered.
Many times we'll find the first set or two of flowers are unproductive with winterized plants (dropping off without producing peppers), but afterward, they quickly become productive and start fruiting. Sometimes this lack of productivity can last upwards of a month. Chances are this is due to daytime/nighttime temperatures not yet being warm enough to support fruiting – in excess of 65-80°F during the day and 55°F at night.
As was done while the plants were indoors for the winter, you'll want to continue watching for the Mosaic virus. Quickly discard any plants that start showing the telltale wrinkled, yellow-spotted leaves that aren't the result of over-watering (usually droopy and yellowed).