Growing Herbs Indoors

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Growing Herbs Indoors

How to have the flavors of fresh herbs throughout the winter

 

Herbs That Grow Well Indoors

Not every herb likes indoor life. Coriander (cilantro), garden

cress, and dill are short-lived annuals that, when cut for harvest,

do not regrow. You have to resow these herbs to produce a continuous

crop. Three pots of each plant, each at a different stage (seeded,

intermediate growth, and ready to cut), are usually enough. Forget

trying to grow coriander, dill, or other spice herbs indoors for

their seeds: They won't set enough to warrant the effort.

 

You can grow parsley in pots, but I prefer to bring in established

plants from the garden at the end of the season. The older leaves

will fall off, but the thick taproot will drive new growth from the

center. However, parsley grown indoors from seed never reaches the

size and productivity of plants dug from the garden. That's why I

dig outdoor plants in fall and bring them inside. Keep the soil

around the taproot intact, and be sure to use a pot that's deep

enough to accommodate the root.

 

Unless light is plentiful, growth of most indoor herbs will slow or

even stop during the winter, even with enough warmth. When growth

slows, reduce harvests and hold back a little on the water. Reducing

the indoor temperature to 60o to 65oF, if possible, also helps.

 

French tarragon and chives in particular benefit from a cool period.

When growth flags in winter, place them in an unheated shed or

garage (or in the refrigerator) for a month or two; freezing

temperatures are fine. When returned to room temperature and good

light, they'll put out succulent new growth.

 

Herbs indoors in window boxes. Plants herbs in their pots in a

window box filled with soil up to the rim of the pots. This system

may seem odd, because the roots can only get at the soil outside

through the holes in the pots. But herbs do precisely that, with

faster and more lush growth than in stand-alone pots. The extra soil

prevents the plants from becoming potbound, humidity and soil

moisture remain

more even, and the herbs seem to grow better. Also, the roots don't

become so intertwined that it's difficult to rearrange or replace

plants. A firm yank dislodges them.

 

How to Grow Herbs Indoors

Herbs are sun worshipers for the most part. As expatriates of the

Mediterranean region, most flavorful herbs don't thrive in the un-

Mediterranean environment and inadequate light our houses provide.

Herbs don't tolerate north-facing windows, or any window that gets

less than four hours of direct sunshine a day.

 

Provide Light

Even if your indoor herbs get their four hours of direct sunshine

daily, installing supplementary lighting is a necessity. The light

coming through a window may seem bright to your eyes, but its

intensity in winter is often less than one-tenth of the outdoor

light during a summer day. Grow lights will work if their light

intensity is high enough and the spectral quality is right.

 

Acclimate Plants Gradually

Plants produce two kinds of leaves in response to strong or weak

light. High-light leaves are thick, strong, and narrow. Low-light

leaves are thinner, more delicate, and broader than high-light

leaves. But narrow high-light leaves are less efficient in

converting light energy into food than low-light leaves. High-light

leaves are accustomed to an abundance of light, so they don't have

be as efficient at food production. A plant that is adapted to

abundant light often turns brown and drops leaves indoors. This is

because it can't produce enough food to maintain itself. The plant

tries to make food by shedding the inefficient leaves and producing

efficient leaves higher up and closer to the light source. When you

bring herbs indoors, this leaf drop and increased leggy growth can

happen within weeks, or even days. Some herbs cannot make the

transition fast enough to survive.

 

Rosemary is a case in point. This slow-growing evergreen doesn't

have the chance to adjust to changes in light before the plant

slowly starves itself. By January, February, or March, the leaves

dry up, and the plant dies. This sudden death is by far the most

common complaint about growing rosemary indoors. Here's what to do:

Gradually adjust the plant to lower light. Place it in partial shade

for two to three weeks, then in deeper shade for another two to

three weeks before bringing it indoors. When plenty of new growth

appears, the plant is ready to go into the house.

 

Soil, Fertilizer, and Water

After light, proper soil is the next most important factor in

producing healthy herbs. With few exceptions, herbs require

excellent drainage, especially during the winter months, when

transpiration rates are lowest (that's the rate at which plants

release water from their leaves to the atmosphere). When roots are

confined in a pot or planter, water and air cannot move easily. To

improve drainage without sacrificing nutrients, add sharp sand or

perlite to a good sterilized compost-based mix. Most herbs do well

in soils of pH 6 to 7.

 

Many people incorrectly think that herbs grow better in poor soil.

Flavors are stronger when culinary herbs grow outdoors in gardens.

But in the confines of a pot, supplementary feedings with liquid

fertilizer or organic fish emulsion are necessary. Feed herbs once a

week when plants are actively growing, but not when dormant.

 

Watering is not a trivial matter with herbs. In general, water less

often and more thoroughly, and only when the soil is actually dry.

When the soil is dry to the touch, add water until it comes out the

bottom of the pot. If the water doesn't come out, pots have a

drainage problem. First, check that the holes aren't blocked; if

not, you may have to repot with soil that has better drainage.

 

Pests and Diseases

Herbs are susceptible to common pests, including whiteflies, spider

mites, aphids, mealybugs, scale insects, and thrips. Inspect herbs

regularly.

 

If your herbs are in portable containers, control pests by dipping

the whole aboveground part of the plant into a pail of insecticidal

soap. Swish vigorously for a minute or two to wet all leaf surfaces

(hold your hand over the pot to prevent soil loss). Dipping herbs

once or twice a week for three to four weeks will clear up most

problems.

 

Newcomers and Old Favorite Herbs to Grow Indoors

In recent years, many new varieties of herbs have been introduced,

some of which do better indoors than the traditional varieties. Here

are 10 herbs notable for their consistent, compact growth habit and

strong flavor.

 

'Grolau' chives (Allium schoenoprasum): Strong flavor and thick,

dark green leaves. Developed for forcing, 8 to 12 inches tall. Seeds

germinate in 10 to 14 days at 60o to 68oF.

 

'Fernleaf' dill (Anethum graveolens): Dwarf form of dill only 18

inches tall. Ideal for dill weed indoors. Standard varieties grow

too tall and bolt too soon. Easy from seeds, germinating in 7 to 14

days at 60o to 68oF.

 

'English' mint (Mentha spicata): Perhaps the best-behaved spearmint

variety (not as invasive as others, and the leaves are broader and

deeper green). Excellent for cooking and tea. Easy to propagate from

cuttings.

 

'Spicy Globe' basil (Ocimum basilicum minimum): Dense, compact form

of basil, 8 to 10 inches tall. Good flavor. Grow from seed;

germinates in 6 to 12 days at 68o to 77oF.

 

Greek oregano (Origanum vulgare hirtum): The true oregano for

Mediterranean cooking, with excellent flavor and white flowers.

Watch out for the impostor (called wild marjoram) with pink flowers

and no flavor. Greek oregano grows well in pots, reaching 8 to 12

inches. Grows easily from seed in 7 to 21 days at 65o to 72oF.

 

Broadleaf thyme (Plectranthus amboinicus or Coleus amboinicus): Also

known as Spanish thyme and Cuban oregano, this plant has broad,

fleshy leaves unlike those of ordinary thyme. Wonderful, spicy thyme-

oregano flavor and useful in many of the same recipes as ordinary

thyme. Never goes dormant. Grows from cuttings only, and reaches 10

to 12 inches tall.

 

Vietnamese coriander (Polygonum odoratum): Not true coriander, but a

good substitute. Regrows after cutting, unlike true coriander, which

must be reseeded after harvest. Grows 4 to 8 inches tall. Propagate

from cuttings.

 

'Blue Boy' rosemary (Rosmarinus officinalis): More compact and

diminutive than regular rosemary, reaching only 24 inches. Flowers

freely and has excellent flavor. Propagated by cuttings only.

 

Dwarf garden sage (Salvia officinalis 'Compacta'): Smaller leaves

and more compact habit than regular sage, growing only 10 inches

high. Same sage flavor. Propagated by cuttings only; seeds are

unavailable.

 

Creeping savory

(Satureja repandra or S. spicigera): Flavor identical to that of

winter savory, but easier and faster to grow indoors. Reaches only 2-

4 inches in height, but fills the pot with a dense mat of foliage.

Difficult to find seeds, but grows readily from cuttings.