If you were the proud grower of basil, parsley and oregano all summer long, there is no need to let your established summer herbs die off with the cool weather. We had our experts answer your questions on the best ways to move herbs indoors and continue to enjoy them all winter long. Here's what you need to know.
Meet the Expert
- Venelin Dimitrov is a horticulturist and senior product manager at Burpee with over 19 years experience in the horticulture world.
- Gladys Mbofung-Curtis is a plant scientist at Spectrum Brands with a Ph.D. in plant pathology from the University of Arizona.
When should you bring herbs indoors?
Herbs such as lemon verbena, basil, dill, and cilantro should be brought indoors before the first frost. Once inside, these plants do best with indoor temperatures ranging between 65-75°F. Several hardy herbs can actually overwinter outdoors, including mint, oregano, parsley, sage and thyme.
“They go dormant before rallying again in the spring, but you’ll need to take precautions so they don’t succumb to frost,” says Venelin Dimitrov, horticulturist and senior product manager at Burpee in Warminster, Pennsylvania. “Herbs in the ground should be placed in a well-drained area and covered with a few inches of mulch. If your herbs are in containers, make sure the pots are made of a glazed clay so they don’t crack with freezing temps.”
Some herbs, such as tarragon, chives, and mint benefit from time in cold weather as it brings on a rest period, followed by fresh growth.
“It’s best to leave them outdoors during the rest period and then move them indoors three weeks post the first frost,” adds Dimitrov. You’ll want to bring rosemary and parsley inside once overnight temperatures settle into the mid-to-low 30s range, and lemongrass and other herb grasses as soon as their top growth starts to turn brown.
Should you prune herbs before bringing them indoors?
Yes. While still outdoors, remove dead or broken branches and diseased leaves, then lightly trim away three to four leaves per branch, along with three to four buds to help activate growth.
Start by gently squeezing off excess dirt around the roots, and then trim the roots symmetrically with a pair of shears before re-potting in fresh soil.
“Don’t remove more than 1/3 of the top growth or you’ll run the risk of reducing the herb’s ability to photosynthesize, stunting its growth,” says Gladys Mbofung-Curtis, a plant scientist at Spectrum Brands in Madison, Wisconsin. “At the same time, if you’re re-potting, be sure to prune 1/3 of the lateral roots to stimulate root growth in the new container.” Over winter, continue pruning the leaves and buds of your herbs to encourage airflow and growth.
What size container works best?
The size of the pot depends on the size of the herb.
“Herbs don’t require a lot of soil and will survive in relatively small containers. In fact, thyme, lavender, oregano, rosemary, and chamomile thrive in the cracks and rocks on the Mediterranean coast,” says Dimitrov.
Containers should be large enough to comfortably hold the roots and keep plants upright when they reach maturity.
“Re-potting should be done in a container that is at least two inches larger than the one containing the plant. A good rule of thumb is to choose a pot that’s at least one-third as tall as the mature plant, and half to three-quarters of its mature width,” adds Mbofung-Curtis.
Do you need fresh soil?
Ideally, you should integrate new soil. “A good mix includes two parts potting soil and one-part perlite or sharp sand,” says Dimitrov. “Many herbs like basil, rosemary, and thyme prefer a nonacid soil, so it’s best to add a teaspoon of ground limestone per 6-inch pot.”
When transferring, begin by placing a layer of the potting mix on the bottom of the container, then set the herb on top.
“Fill in the spaces around the roots with more potting mix and press the soil firmly down around the plant's roots, leaving about an inch between the soil and the rim of the pot. Water until it drains out onto the saucer,” notes Mbofung-Curtis.
Should you ease your herbs indoors?
An abrupt change in their environment can be stressful to herbs, resulting in yellowed leaves, wilting, and even death. Place potted herbs in a partly shady area outdoors for a few weeks before moving them inside.
“Bring them indoors at night for the first few days and take them back outdoors during the day when temperatures are not yet at a freezing point. Gradually increase the number of days the plants spend indoors, setting them up indoors in an area with indirect light,” says Mbofung-Curtis. “After a couple of weeks, you can move the pots to a spot with more direct sunlight.”
How much sunlight do herbs need?
Place potted herbs in a southern-facing window where they’ll receive six to eight hours of light. If you don’t have that kind of access to the sun, supplement with grow lights. “You can use regular fluorescent tubing, hung twelve inches above the plants, or more energy efficient LED lights placed six inches over your herbs,” says Mbofung-Curtis.
Set a daily timer and rotate the pots regularly in order to expose all sides of the plant to the light source. “Adjust the placement and height of the lights as your herbs develop and mature,” adds Mbofung-Curtis. “A sign an herb is not receiving enough light is the presence of ‘leggy’ stems that are white or yellow in color.”
How often should you water herbs?
While herbs are famous for being drought tolerant, they still need watering. “There’s no easier way to find out if they’re thirsty than by sticking your finger in the soil,” says Dimitrov. “The top few inches should be dry but then you should hit moisture.”
Many herbs, including marjoram, oregano, sage, bay and thyme, will benefit from letting the soil surface dry a little between watering, though not to the point that the leaves wilt. Basil, dill, and rosemary cannot dry out completely or you’ll have trouble reviving them, while mint and lemon balm like a more consistent moisture. Misting the leaves daily with water will increase moisture levels and slow leaf droppings.
How can you prevent bugs from coming indoors?
Inspect the tops and undersides of the leaves, joints, stems, pots and saucers for any indication of pests, such as webbing, small bumps, or unusual discoloration before moving herbs indoors. “While herbs are still in the ground or in containers, rinse them well with a garden hose,” suggests Mbofung-Curtis.
If necessary, treat pests such as aphids, mealybugs, mites and leafhoppers with an insecticidal soap such as Garden Safe Insecticidal Soap Insect Killer ($7), and any fungal issues such as black spot, rust, and powdery mildew with a fungicide like Garden Safe Fungicide3 ($5). While indoors, herbs can still fall victim to fungi or insects such as spider mites so continue to inspect your plants throughout the winter.
Is there an adjustment period when moving herbs indoors?
Yes! “Herbs need time to adapt to their new surroundings,” says Mbofung-Curtis. “So don’t be alarmed if they drop leaves and develop more slowly once inside.”
Can you grow new herbs during the cold season?
Snipping sprigs encourages the herbs to produce new growth and stay compact until you can move them outdoors come spring. Even better, you can use these sprigs to expand your supply of fresh herbs.
“Simply take cuttings of soft-stem herbs like basil, lemon balm, and mint and place them in a small vase of water while they develop roots,” suggests Mbofung-Curtis. “For herbs with woody stems such as rosemary, sage, oregano, and thyme, make sure the cuttings are green as brown stems will not sprout root as easily. When the roots are a few inches long, pot the cuttings.” Sadly, stems from herbs like parsley, dill and cilantro will not root with this method as they’re propagated by seed.