Growing Herbs Indoors

Potted Herbs

Not all herbs do well indoors but with just a few containers of these tasty plants you can have a supply of fresh herbs all winter long.

With this in mind, you may want to consider something different for those people special in your life, like some herbal oils or vinegars. They make great gifts for the holidays and are a great addition to your own pantry. (see http://valleyseedco.com/623/creating-herbal-vinegar/ for ideas)

Short lived and single cut herbs like Cilantro and Dill do not regrow after cutting. You’ll need to start  herbs like these in stages to produce a continuous crop. A pot (or two) of each plant at seeded, intermediate growth, and ready to cut are usually enough. Trying to grow spice herbs indoors for their seeds probably isn’t worth your time—they simply don’t set a lot of seed.

Unless light is plentiful the growth of most indoor herbs will slow or even stop during the winter even if warm enough. When growth slows, reduce harvests and hold back a bit on the water. If you can, reducing the indoor temperature to 60 or 65F will also help.

i.e. French tarragon and chives benefit from a cool period. When growth lags in winter, place them in an unheated shed or garage for a month or two; freezing temperatures are not a problem. When returned to room temperature and good light, they’ll put out plenty of new growth.

Parsley can be grown in pots but using an established plant from your garden will make a tremendous difference. The older leaves will fall off, but the heavy taproot will encourage new growth from the center. Keep the soil around the taproot intact and make sure to use a pot that’s deep enough to accommodate the root. Parsley grown indoors from seed will not reach the size and productivity of plants dug from the garden.

I saw this idea somewhere—at first it didn’t make sense and then I thought about it—and think it’s a good idea.

Make sure your pots have good drainage and therefore good sized drain holes (drill the holes larger if you need to) plant the herbs in their pots in a box filled with soil right up to the rim of the pots. The herb roots can only get at the soil outside through the holes in the pots and they do exactly that, which results in faster and better growth than in the pots alone. Being able to spread their roots prevents the plants from becoming root-bound and soil moisture stays more even. If the roots get tangled it’s easy enough to separate them with a firm tug on the pot. We found some tubs that measure about 16” deep, 16” wide and 26” long that should work well for this. It was easy to get 6 herb pots in each.

As a rule, herbs love full sun. Most originated in the Mediterranean and by design our houses do not provide enough direct sunlight for an herb to thrive.  If you decide to grow herbs indoors you need to put them in a window that gets 4 hours (or more) of direct sunlight each day.

Even if your indoor herbs do get four hours of direct sunlight daily, using supplementary lighting is going to be necessary. The light coming through a window may seem bright to you, but its intensity in winter is less than one-tenth of the outdoor light during the summer. Grow lights will work if their light intensity is high enough and the spectral quality is right. For instance—fluorescent bulbs range in intensity of about 4000k to a daylight spectrum of 6500k. Go for the 6500k.

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 to be as efficient at food production.

A plant that is used to abundant light often turns brown and drops leaves when brought indoors. This is because it can’t produce enough food to maintain itself (photosynthesis). The plant tries to make up for this lack of light by shedding its lower leaves and producing leaves higher up and closer to the light source. When you bring herbs indoors, this leaf drop and increased leggy growth can happen seemingly over-night. Some herbs can’t make the transition fast enough and will die off.

This sudden death is the most common problem with growing herbs indoors. Gradually adjust the plant to lower light by placing it in partial shade for two to three weeks, then in deeper shade for another two or three weeks. When you notice new growth happening, the plant is ready to go into the house. (this is exactly the opposite of “hardening off” a plant in spring before moving it outdoors.)

With few exceptions, herbs require excellent drainage, especially during the winter months, when transpiration rates are lowest–the rate at which plants release water from their leaves. To improve drainage, add coarse sand or perlite to a good sterilized compost-based mix. Most herbs do well in soils of pH 6 to 7.

Many people think that herbs grow better in poor soil. Flavors are stronger when herbs are grown outdoors in gardens. But when in a pot, feed with liquid fertilizer or organic fish emulsion (works really well but is a bit smelly) about every second week. If the plant goes dormant stop fertilizing.

In general, water less often and give them a good soak, 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 (see drainage above). If the water doesn’t come out, the pot has a drainage problem. First, check to see if the drain holes are blocked; If they’re not plugged you’ll need to repot with soil that has better drainage.

Herbs are susceptible to common pests–whiteflies, spider mites, aphids, mealybugs, scale insects, and thrips etc. Check your herbs on a regular basis to prevent these pests getting out of control. If your herbs are in portable containers, control pests by dipping the whole above ground part of the plant into a pail of insecticidal soap. Keep underwater—moving around gently so as not to break off branches or leaves– for a minute or two to wet all leaf surfaces (Be sure to keep your hand over the pot to keep the soil from falling out). Dipping once or twice a week for three or four weeks will clear up the majority of problems.

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