Many herbs are well suited to domestic life and thrive indoors. With some attention to their special needs, you can keep an indoor herb garden that will give you fresh herbs year round.
Indoor Herb Lighting
The biggest challenge to the indoor herb gardener is light. Lighting is critically important to all plants, but herbs seem to be especially sensitive to the right light conditions. If you can just manage to give your herbs effective lighting, you're 75% of the way to having a great indoor garden.
Stick with me here. I'm going to give you a brief primer on lighting.
Your home has windows that have a directional orientation. This angle for sunlight is called exposure. Your room's exposure has a big impact on how much good light your plants receive. An eastern exposure is wonderful because it provides clear, bright light that isn't too hot. Western and southern exposures are also effective, although they are sometimes at risk for becoming too hot and bright during the summer season. The least effective exposure comes from the north. Northern exposures have weak light, and plants near northern facing windows are at risk of getting too little light to stay healthy.
Distance From a Light Source
This leads to another consideration, distance from a light source. Having good light only works if the plants are close enough to benefit from it. After you get a couple of feet away from a window, light quality starts to drop quickly. In order to give most of your herbs the light they need, they have to be pretty close to windows with good exposures. The only exception to this is in southern and western facing windows in high summer when the sun is very hot. (In this instance, move plants back from the windows, or filter the light through shades or sheers.)
Some other thoughts related to light are how clean the windows are, and if there are any obstructions that will weaken the light your plants receive. Awnings, curtains, blinds, exterior shrubbery, and other buildings can all thwart your efforts to give your plants good light if they block a substantial amount of light from entering the room.
What's Enough Light for Indoor Herbs?
Plants need at least six hours of good light each day. The light should be bright enough for your hand to create a well-defined shadow when you pass it between the window and your plants.
What To Do if Your Indoor Herbs Don't Get Enough Light
The simple answer is to supplement with grow lights. This used to be a very expensive proposition, but prices for grow lights and fixtures have come down in recent years.
I put a couple of my lamps on 24 hours timers. That way they are giving my plants eight hours of light when I'm not around to be irritated by the glare. This works great, and the plants flourish. I don't want to quote prices because costs for goods are always changing, but my set-up cost less than a good dinner out for two.
Keeping Herbs Watered
The right water regime is crucial for plants to thrive. Water is an area where one size does not fit all. You have to experiment for a couple of weeks to see what watering schedule each of your plants need. The finger test is still a great way to tell if your plants need water. Stick your finger into the dirt near the rim of your plant's pot to a depth of about an inch and a half. If your finger comes out dry, it's time to water. If your finger is moist, wait a day or two and try again.
After a few tests, you'll have a good idea of how often you need to water a particular plant. . . for the time being. Just be careful to keep up your detective work as the seasons change. Once you turn on the heat in winter or the air-conditioning in summer, start opening windows, or move your plant, chances are its watering needs will change.
Fertilize Herbs Sparingly and Use good Potting Soil
Plants need nutrients in their soil and occasionally through the addition of fertilizer. Herbs are usually less prone to needing frequent feedings, but they still need a quality potting mix and some fertilizer incorporated into their water occasionally.
If you are over wintering outdoor potted herbs inside, be sure to check them for pests before you relocate them. You should also stop fertilizing them as frequently as they will be experiencing some shock from the move and won't need as much nourishment over the winter anyway.
Potting Herbs to Bring Indoors
If you are potting herbs to bring indoors, select pots that are only a few inches larger that the herb's root ball. Herbs are inclined to be more comfortable with crowded roots. Try to avoid terra cotta pots. They absorb moisture and can dry out plants prematurely.
Plants need some humidity in the air. To make sure your herbs are getting the humidity they need, place a few of them on dishes filled with stones or marbles and water. This makes mini-reservoirs that will keep the air around your plants moist. Just be careful to keep the level of the water in the dishes below the bottoms of their corresponding pots to avoid root rot. Grouping your herbs together can help too.
Harvesting Indoor Herbs
Use restraint when harvesting your indoor herbs. Pay attention to new growth, and try to avoid taking more than half. If you discover that isn't enough, it's time to get another plant.
I've written a post for my houseplant blog that will give you more help on evaluating your indoor plant space for sunlight, heat, and humidity. Take a look if you have a moment: Houseplant Care – Evaluating Your Environment.