Yes, your sage plant can not only survive winter indoors but thrive with the correct care. From our perspective as plants, the sudden shift from the outdoor growing season to the indoor environment is a significant shock to our system. Success depends on you understanding and replicating the conditions we need to enter a healthy dormancy or subdued growth period.
Please do not wait for a hard frost to bring us inside! That cold damage makes us vulnerable. The ideal time is before night temperatures consistently drop below 50°F (10°C). This gradual cooling outdoors helps us start to harden off, but a sudden plunge is dangerous. Moving us inside while it's still moderately warm outside gives us a much better chance to acclimate to the less intense indoor conditions without going into severe shock.
This is the most critical factor. Outdoors, we bask in full sun for 6-8 hours. The light through your window is drastically reduced in intensity and duration during winter. A south-facing window is our best bet for the strongest available natural light. However, it often isn't enough. Without sufficient light, we become leggy, stretching weakly towards the light source, and our leaves may yellow and drop. To truly help us survive, consider supplementing with a grow light for 12-14 hours a day to compensate for the weak winter sun.
Our water needs change dramatically indoors. With cooler temperatures, lower light levels, and likely higher humidity, our growth slows nearly to a halt. Our roots are very susceptible to rot in cold, wet soil. The key is to let the soil dry out much more thoroughly between waterings. Check the top 1-2 inches of soil; it should be completely dry before you even consider giving us a drink. When you do water, do so thoroughly but ensure we are never sitting in a saucer of water. It is far better for us to be slightly too dry than too wet.
Your heated home presents a double-edged sword. The air is often very dry, which we find stressful and can lead to crispy leaf edges and attract pests like spider mites. However, the temperature is likely perfect. We prefer indoor temperatures between 60-70°F (15-21°C). Please keep us away from both hot, drying drafts from heating vents and cold drafts from leaky windows. To combat dry air, you can place our pot on a pebble tray filled with water (ensure the pot is not sitting in the water) or occasionally mist the area around us.
Please, withhold the fertilizer. We are not in an active growth phase and cannot process those nutrients. Feeding us now can lead to a harmful buildup of salts in the soil and can force weak, spindly growth that the low light conditions cannot support. Similarly, avoid any major pruning. You can pinch off the very tips of stems to encourage bushiness and always remove any dead or yellowing leaves to keep us healthy and prevent disease, but save the hard pruning for early spring, just before new growth begins.
