In spring, overwintered potted plants and new plant starts go through a process called “hardening off”. This process involves gradually acclimating the plants to life outside where light is brighter and wind is stronger and temperatures fluctuate through a much wider range than the plant would ever encounter indoors. I have found that repeating this process in reverse every autumn is very beneficial to my indoor/outdoor potted plants such as white sage, bay laurel, and citrus trees. I’m not aware of an official term for this reverse process, so I’ve taken to calling it “softening up”.

Timing and Division

Nighttime lows have begun to dip into the high 30s in my area, and that’s my cue to begin the softening up process. Since I have many potted plants, I divide them into three groups to minimize the amount of time I have to spend moving planters every day. The first group will require the longest softening up transition, and should be spending most of its time indoors by the time I begin transitioning the second group. The second group will require a shorter transition, and the third group requires very little transition at all.

Extra Care For The Most Delicate Plants

The first group consists mostly of tender evergreen herbs. These plants are the most sensitive to environmental shifts, and require the most delicate care during the softening up transition. Most of the Mediterranean herbs will fall into this category: bay laurel, sage, rosemary, and lavender for example. White Sage, a California native plant, also responds well to this treatment. These plants appreciate a two week softening up process, and for me, that begins right now.

Note: I also bring these arid climate plants indoors if rain is in the forecast during the softening up period, because in past years I have observed that a soaking rain can moisten the potting soil so thoroughly that it may take a month or more to fully dry in the cooler, damper environment of my home. Since these plants are mostly from arid climates, they do not appreciate that long wet period, and may suffer root rot or fungal infection if that happens. When I water them manually, I am able to control the amount of moisture these plants receive so that they will not have wet feet for long periods of time. Perhaps if you grow your plants in very sandy potting soil, or if your home is very dry, rain may not be an issue for you.

Faster Transitions for Hardier Plants

My second group consists of tougher plants that are frost-tender, but not as sensitive to shock as the first group. My second group consists mostly of citrus trees and succulents. I grow lemon, orange, lime, aloe, and dragonfruit in pots, and I find that those are all very resistant to shock, but they appreciate a little bit of softening up and will reward you with greater vigor if you treat them gently. These plants respond well to about a week of softening up. I don’t find it as necessary to bring these plants indoors before rain, unless the root system hasn’t yet filled the pot it is in.

Winter Care For The Easy Going Plants

The easiest plants to transition are those that naturally shed their leaves and go dormant over winter. For these plants, it’s not a big deal if they experience a transition shock and lose their leaves a little early. They tend to bounce right back in the spring. I generally leave these plants outside until they are almost totally dormant, only bringing them in if there’s an actual frost in the forecast. Some types of plants that often fall into this easy care group include figs and other deciduous trees, bulbs, tubers, and rhizomes.

The Softening Up Process In Detail

Step 1: Ideally, before beginning the softening up process, examine all the plants you plan to bring indoors. If they have any insect infestations, it’s easiest to tackle this now while they’re still outdoors. Any mess you make will remain outside, and you can avoid creating a new infestation in your home. If you can’t do this right now, then I doubt will cause a true disaster. The worst that has ever happened to me involved spending an afternoon scrubbing up plants in my bathtub, or setting out a trap for fungus gnats.

Step 2: In the evening, I round up the potted plants that I am currently softening up. I take them all indoors to spend the night in the house. Early on in the softening up process, I may take the plants back outside in late morning, so they can spend most of the day outside. Midway through the softening up process, I begin keeping them indoors until early afternoon. Towards the end, I will keep them indoors until late afternoon and give them just a few hours outdoors.

Step 3: When the plants have been fully acclimated, I bring them all indoors one last time. I place them in their permanent winter places where they will stay until spring. I keep my dormant plants in the basement, since they don’t require much sun or heat. I place other plants as close as possible to sunny windows. I have experimented with adding artificial lights, but none have worked out for me. They don’t seem to provide enough benefit to equal the expense and difficulty of their use. I find that although my plants don’t really thrive and grow vigorously in winter window light, they do survive this way until spring and will resume their vigorous growth patterns when they return to their outdoor lives. However, if you don’t have adequate window light, you might find grow lights to be an important part of your overwintering strategy.

If you’re interested in learning more about container gardening, you might enjoy these other articles from The Strawberry Moon Blog:

DIY Recycled Seedling Pots
DIY Plant Stand: How to build a convertible plant stand, potting bench, or boot bench
The Quest For Dragon Fruit (Pitaya)
Improved Meyer Lemon Tree