by Elisa Hawkes
Coastal Journal staff
As the weather grows cooler, Mainers know nights will soon become frosty. Plants taken outside for the summer, or those labored on for the past four months in gardens, will soon be ready to journey indoors for the winter.
Many indoor plants are actually tropical, and highly sensitive to temperatures beneath 45 degrees Fahrenheit (F). Other outdoor plants are tender, especially in our hardiness zone, and must be taken inside to survive harsh northern New England winters. A hardiness zone is a geographical area defined by climatic conditions, including minimum temperatures and the first and last frost dates. Specific categories of plant life are capable of growing in different Zones, numbered one through 12. The lower the zone number, the harsher the weather.
There are three distinct zones in Maine: Three, Four, and Five. For the most part, the Midcoast is in Zone Five, meaning the United States Department of Agriculture (USDA) has determined the minimum temperature to be around -20 degrees F. When purchasing plants for the garden, it is important to know the hardiness zone. If a plant is too tender to overwinter, it should be taken inside to plant again next summer. Or the plant may remain in its pot, and simply spend the summer out of doors.
Changing the location of plants from outdoors to indoors is a fairly simple procedure, but must be done in stages, or plants will experience shock and may not survive the experience. Outdoor and indoor conditions are very different in terms of temperature, light, and humidity. All three factors greatly affect the well-being of plants, and must be changed gradually.
Transition from outside
Try the following steps to transition plants from outside to inside to avoid leaf loss, yellowing, drooping, and the possible demise of the plant.
1. Check the plant for “creepy-crawlies.” Many plants will pick up aphids, spider mites, and more. Remove what you can, then wash the plant with the garden hose. If you are digging plants from the garden, rinse the roots, also. This will remove any pests you may have missed, and keep them from infecting your houseplants.
2. If a plant has outgrown its pot over the summer, either prune the plant and roots, or plant in a larger pot. Never prune more than one third of the plant, and prune as much root as you do foliage. Repotting should be done in a container at least two inches larger than the current one.
3. Repotting should not be done with just garden soil. It will become rock hard. Use a combination of potting soil and vermiculite for best results, and leave some garden soil around the roots.
4. Start acclimating plants to indoor conditions with a few “sleepovers.” Several nights in the house, followed by days outside will begin to get plants ready to come inside. Gradually increase the time plants spend indoors over the next week or two, until they stay inside permanently for the winter.
5. Plants will need less water inside than they did outside. Growth slows during the winter, also cutting down on the need for water. Some plants go into a hibernation state and do not need to be fed. Water when plants are dry to the touch.
Indoor Herb Garden
Bringing tender herbs indoors for the winter introduces good smells, tastes, and beauty into the house. It brings a little bit of the summer garden in to brighten the winter. Some hardy herbs are fun to grow, also.
While it can be difficult to grow herbs indoors, over the years I have pieced various bits of advice together and have successfully grown herbs from fall through spring. Here is what I’ve found:
1. Most herbs love sunshine, so put them in the sunniest window in your house. Be careful, however, not to place them too close to the glass. Cold air radiating through the glass can damage tender herbs. Hardier varieties, such as thyme and oregano, may not mind as much as rosemary. Thyme can winter outside. Rosemary will not survive the cold Maine winter.
2. Don’t bother with annuals, unless you really want basil, mint or other herbs. Annuals usually become leggy, and don’t produce much inside. They do, however, emit wonderful scents.
3. Do not cut back rosemary, bay, or other tough-leaved plants before bringing inside. Leafy plants, such as oregano, should be cut back before coming inside.
4. Humidity is the most important factor for many herbs. Make sure to mist often. Try placing pots on a pebble tray so evaporating water will add moisture to leaves. This is especially important with rosemary, which does not like wet soil, but does like humidity.
5. Don’t overwater. Wet soil will cause mold and rot. For the same reason, don’t let old leaves collect in the pot.
6. Remove dead or yellow leaves frequently.
7. Lemon verbena must be wintered inside. Since it’s deciduous, lemon verbena will drop its leaves within a few weeks of being brought indoors. Just move the plant to a cool place out of the light until March. Bring it out, give it sun, water it, and it will put out all new growth.
8. Try growing some herbs in pots all summer. The transition from outside will be a lot easier for them.
Winter does have to mean gardening is over for the year. The beauty of green leaves, flowers, and delicious additions of fresh herbs to recipes can continue throughout the year. All it takes is a little preparation.
Remember, break the idea of coming inside to your plants slowly, bringing them in a little at a time, give them plenty of sun and moisture, don’t overwater, and they’ll wait out the winter with you.