It began innocently. Like many gardeners, Herb Companion reader Becky Short couldn’t bear to part with the flavors and fragrances of her favorite herbs when frosts arrived at her Macungie, Pennsylvania, garden. After years of digging and potting rosemary, scented geraniums and other plants each fall, she decided to take the next step: Becky created a winter garden indoors—an entire room devoted to potted herbs, tropicals and other treasured plants.
“It’s my favorite place to be in winter,” Becky says. “Surrounded by the scents, green leaves and oxygen they release—it’s like being in the garden. I love it.”
Growing Under Glass
People have been building shelters for protecting, or conserving, plants in winter for centuries. Early conservatories sometimes were called “orangeries” because they often housed citrus and other tender fruits. At first, only British and French nobility enjoyed them, but in the 20th century, conservatory sunrooms became more affordable and popular. In contrast to a three-season patio sunroom, a conservatory sunroom is constructed for year-round use—generally with a separate heating and cooling system, glass walls and a glass roof.
Designed and built by British Conservatories in 2004, Becky’s 14-by-16-foot attached conservatory provides ideal indoor growing conditions. The room receives bright southern light and is completely covered with glass overhead. Temperatures range from 55 to 80 degrees. In summer, she opens the roof and side windows and runs a fan to keep daytime temperatures from rising too high; at night, when temperatures dip, wall heaters kick on to remove the chill. A brick floor allows generous, worry-free misting and watering.
A Taste of the Exotic
Becky takes advantage of the room’s abundant light and warmth to experiment with unusual herbs that would not survive her Zone 6 winters outdoors. Tropical herbs thrive here, producing rich fragrances and full flavors.
In one corner, stevia (Stevia rebaudiana) bears a profusion of attractive, bright green leaves that taste sweeter than sugar. Nearby, Cuban oregano (Plectranthis amboinicus) drapes its sprawling stems over the edge of a terracotta pot; Becky sometimes pinches off a few of its velvety leaves to add a pungent note to Mexican dishes. A lush coffee plant (Coffea arabica) is covered with beautiful, glossy green foliage, but “no berries, yet,” Becky says.
Other indoor favorites include snow rose (Serissa foetida), a diminutive tree with tiny leaves and pink blooms, and Vick’s plant (Plectranthis tomentosa), a strong-smelling succulent herb. The conservatory also houses more familiar herbs, such as prostrate rosemary, bay laurel and a multitude of scented geraniums (Pelargonium spp.).
NEXT PAGE: Becky's top choices, glass room lessons and how to properly bring your outdoor garden indoors.
The Victorians loved to bring scented geraniums indoors, Becky reminds us: “They lined their hallways with them, and as the ladies walked by, their skirts would brush the leaves, releasing their wonderful scents.” Her top choices include ‘Lemon’, ‘Rose’, ‘Apple’, ‘Lime’ and ‘Snowflake’. Becky puts some of the leaves in sugar to impart subtle flavor and fragrance; she also places leaves on the bottom of cake pans, before pouring in batter, for a decorative and tasty effect.
Glass Room Lessons
In Becky’s “living room,” most herbs are carefree, thriving in standard commercial potting mix. With less daylight in winter, plant growth slows, so less water and fertilizer are needed than during spring and summer. In fact, Becky does no feeding at all until active growth resumes in late winter, and she waters most plants only every two weeks. “That’s also because individual plants need less water when so many plants grow together in one area,” she says. “But I do mist frequently because humidity usually is low in winter.”
An occasional outbreak of mealy bugs is rubbed out with a dab of dish detergent on a moist paper towel, applied to affected foliage and stems. (Other effective organic treatments for mealy bugs, scale or spider mites include a strong spray of water, insecticidal soap spray and light horticultural oil.)
Because Becky’s glass-room plants remain in pots year-round, moving them in and out of the conservatory as the seasons change is a breeze. At the end of summer, she simply prunes back some of the lush top growth before moving the plants back indoors, “mostly so I can fit them all inside.”
The biggest challenge? “It’s become something of a shelter for friends’ and neighbors’ plants,” Becky confesses, with a laugh. “… it’s difficult to say ‘no.’”
Bring Your Garden Indoors
Most herbs are tough by nature, but some take to an indoor climate better than others. Don’t bother with annuals, such as basil, dill or cilantro; these herbs already have exhausted themselves in the garden.
Instead, focus your over-wintering efforts on 1) tender perennials, such as rosemary, bay, tender lavenders and lemon verbena; and 2) herbs that are compact and/or have trailing stems, such as thyme, mint and winter savory.
Another option is to start with new potted herbs. If you can’t find them at a local greenhouse, contact these mail-order suppliers: Richters (ships to November 15), (905) 640-6677, www.richters.com; Well-Sweep Herb Farm (ships year-round), (908) 852-5390, www.WellSweep.com.
NEXT PAGE: Don’t have a sun room or conservatory? No worries. If you can grow herbs outdoors, you can grow them indoors this winter; just follow these simple guidelines.
7 Easy Steps Inside
Don’t have a sun room or conservatory? No worries. If you can grow herbs outdoors, you can grow them indoors this winter; just follow these simple guidelines:
1. Beat the frost. Aim to dig and pot your plants at least a few weeks before your first expected frost. Better yet: Bring herbs indoors when outdoor daytime temperatures are 65 to 70 degrees—about the same as indoor temperatures.
2. Choose the right pot. Choose a container slightly larger than the root ball of the plant; or use a large window box-style container to hold several smaller herbs. Plastic pots are lighter and more portable than terracotta; they also retain water better than unglazed clay pots. Remember that plants need less water in winter, however. If your home tends to be warm and dry, choose plastic pots; if it’s cool and humid, terracotta could be a better choice. Be sure any pot you use has drainage holes.
3. Provide a good mix. Use a good-quality commercial potting mix—or a homemade blend of compost, vermiculite and peat moss—but never garden soil. Garden soil often is too heavy, drains poorly and can harbor insects, disease pathogens or weed seeds. Moisten the mix before you pot your plants.
4. Spray away insect pests. Don’t risk bringing pests indoors. After potting garden herbs, spray them thoroughly with a soap-based spray to keep scale, mealy bugs, spider mites and other common pests from hitching a ride inside. Contributing editor Susan Belsinger makes a preventive spray of soap, garlic and chiles. (For the recipe, see her article “Defend Your Garden with Herbs” at www.HerbCompanion.com.)
5. Take time to trim. Now is also a good time to give plants a light “haircut”—trim back the top third of plants to encourage strong new growth, and to help compensate for root loss.
6. Move gradually. Your plants will barely notice the change if they have time to adjust gradually to their new conditions. Just as plants benefit from “hardening off” (gradual acclimation) in spring, they do better with a similar but reverse process in fall. If possible, start by moving them to a bright but sheltered location outdoors, such as beneath a tree, for a week before moving them indoors.
7. Head south. For best results, replicate outdoor growing conditions as much as possible. Choose a bright, south-facing window; or place plants 4 inches below a fluorescent light fixture. Avoid a location directly adjacent to a heat source, which can dry soil and stress plants.
Vicki Mattern is editor of The Herb Companion. Rob Cardillo is a photographer who lives and gardens in southeastern Pennsylvania. To contact him, visit