Below is a very brief summary on how to grow closet herbs. At a high level, it covers the basic process for growing soil-based herbs indoors.
Potting soil – Nutrient-rich potting soils like Fox Farms Ocean Mixture or Miracle-Gro are very popular, and it’s easy to put it into 8 inch pots for planting. Plain outdoor soil can be used, but it’s very low in nutrients, and would need to be heated to about 150 degrees for at least 20 minutes to kill any unwanted pests that may be in it.
Use the best quality herb seeds – Quality plants begin with quality seeds. Seeds for many high quality herbs can easily be mail-ordered. “Feminized” seeds are the best, as they virtually guarantee your plants to be feminine in gender and not the worthless male plants that should be thrown away.
Germinating herb seedlings – Poke a hole about 3/4 deep into your potting soil, drop one seed into it, cover lightly with soil, and water. It’s important to keep the soil moist – but not necessarily soaked – at all times during the germination stage, which can last as long as ten days. (Some growers insist on germinating seeds on wet paper towels and transplanting them once they’ve sprouted, but it’s unnecessary work and you run the risk of killing your delicate sprouts if the paper towels dry out.)
Use fluorescent and HPS lighting – During the early vegetative growth stage, fluorescent lights work well for getting rapid growth out of your herbs. Later on, when your herbs are ready for the flowering stage, switch them to high pressure sodium (HPS) lighting which has a shorter, redder wavelength. You can use fluorescent throughout your growing cycle, but it will reduce your ultimate herb yield when it’s time to harvest.
Nutrients for herbs – All plant fertilizers contain nitrogen (N), phosphorous (P), and potassium (K). When you read the label, you’ll see the ratios of each of those nutrients listed in an order similar to 2-4-8, 2-1-1, or something similar. While in the early vegetation stage, herbs need more nitrogen and phosphorous than potassium. In the subsequent flowering stage, the plants need more potassium to help their flowering process. You can use either powder-based or liquid fertilizers with equal confidence.
Water your herbs – Using tap water is perfectly fine as long as you allow the chlorine in it to evaporate overnight, and it must be at room temperature when watering your plants. Once you’ve mixed your nutrients with the water, make sure that the ph balance of the mixture falls somewhere in the slightly acidic range (between 6 – 7 ph). If your mixture is too alkaline, add phosphoric acid to it, or something similar like white vinegar.
Herb temperature – Being pretty hardy, herbs will flourish if they’re kept within a reasonable temperature range of 10C (50F) – 32C (90F). If you keep your grow closet hotter, you’ll probably need to water them more often.
Herbs and CO2 – Many studies have shown that using CO2 in your grow closet can increase your herbs’ vegetative process by almost 25%.
How to prune your herbs – Since the broad leaves of your herbs are used for photosynthesis, you’ll want your grow lights to penetrate as far down into your plants as possible. Most growers only prune their herbs to increase the flow of light to lower plant levels.
Flowering your herbs – When growing outdoors, the plants will automatically begin to flower when they sense fall approaching (the days get shorter and dusk comes earlier each evening). If growing indoors, simply switching from an always-on light schedule to a 12 hours on / 12 hours off schedule will trick the plants into thinking fall is approaching, and herbs will begin to form.
Harvesting and trimming – After your plants have matured fully and you’ve cut them down, trim away any organic material that looks withered, rotten, or otherwise useless. A sharp pair of scissors or shears will do the trick nicely.
Drying & curing herbs – Once trimmed, hang your harvested plants upside down in a dark, room-temperature space where air can circulate freely around them. When you can snap off a couple of stems cleanly instead of just bending them (usually within one or two weeks), your plants are ready for use.
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