If you love fresh spaghetti sauce or pesto, then you've just got to have fresh basil and other herbs all year round! A nice window garden getting at least 4 or 5 hours of direct light from a sunny window will give you something to pinch here and there. Gardens with mint, rosemary, bay leaf, savory, oregano, chervil, basil, and thyme are some of the easiest to grow this way.
Provide adequate light. The goal is a vegetative light cycle (18 hours of light at least), with eight or more hours of direct sun or bright artificial light. If you need lots of an herb, you will need to take care of the herb's lighting needs. For example, basil and coriander (cilantro) need just a bit more light than other herbs, and really prefer 8 hours or more of direct light each day. In addition to this, if you want fresh pesto, just a pinch here and there is not going to cut it. Here's what you can do about it:
Whenever the light levels are low, give them a boost. Two or three fluorescent lights above your plants will greatly increase growth and yield. You can grow enough basil for a few servings of pesto now and then and still have enough always at your fingertips.
With a small metal halide light, you would have a larger area with better lighting. You could produce an abundance of any herbs you choose for your culinary and aromatic delights. Basil would take well to the bright conditions under a metal halide, as it is a Mediterranean, sun-loving herb.
Select the proper soil. Some herbs grow better in poor soil, as they can develop a stronger flavour. The oils in herbs make them special. Very fast growing herbs often grow plain leaves and stems more quickly than they can produce tasty essential oils. Often you will hear, "Basil grows better in poor soil," or, "Your basil will taste better if you don't fertilize". What is really meant here is, "Don't grow your basil too fast." (Basil is an example to which this applies).
Correctly set up your containers. When growing in a container it is a little different. The plant still needs some food to grow, and when that food runs out you will need to fertilize. However, as you will see next, this is all taken into consideration together with the growth habits of your herbs:
To keep initial growth rates in control, use a soil mix with just enough nutrients. Mix 2 parts coir (coconut fibre) compost to 1 part perlite, and then add 20 percent worm castings. Test the pH of any mix, and if it is acidic, add one gram of hydrated lime for every litre of soil mix. Or, you can substitute with vermiculite, which does not need pH adjusting. Finally, add 1 tablespoon of kelp meal for each gallon of soil to add plant hormones and to give beneficial micro-organisms something to feed on. Use this mix whenever you transplant.
Know when to water. If the surface of the soil feels dry, you need to water. Another way to tell is to pick up the container and check how heavy it is. Your herbs like their soil to drain fast. You need to have containers with holes in the bottoms, and you need to add a layer of broken roof tiles (slate is ideal) or other small flat stones, or a centimetre or so of perlite or gravel to the bottom of each container as you transplant. It is best to water thoroughly but less often. Water the container until some water comes out of the bottom, but don't over-water.
Start feeding your plants after 10 or so days. When the herbs have been in any container for ten days or more, you need to begin feeding them. In a container, the roots are stuck in a small space and will quickly mine it free of any nutrients, especially if you have been going easy on the nutrients to begin with. Feed with half-strength nutrient such as Maxsea 16-16-16 every two weeks.
Give an additional boost to your herbs. If you really want to keep your plants healthy, it is recommended to use 10 ml/gallon B1 plant mix and liquid seaweed in every drop of water you give to your plants. The B1 consists of vitamins and root hormones, and the seaweed is trace nutrients and plant growth hormones. This will help with essential oil production. Finally, water basil from around the base; it does not like water on its leaves.
Use your herbs when they're ready. As soon as the herbs have grown enough leaves to be pinched without affecting their growth, you can begin using some of the herbs. This usually takes about 4 to 6 weeks, depending on the herbs. Herbs like basil are best when harvested before flowers open. You will get your highest essential oil levels when you harvest at the end of the dark period, assuming you do not leave the lights on 24 hours a day.