Popular Herbs Grow Happily Indoors

By Conrad Richter

Weeds in their native, sun-drenched habitats of the world, most herbs actually grow quite well outdoors in Canada, much to the surprise of uninitiates and to recent immigrants from those lands.

Of course, with the Canadian phenomenon of snow, ice and the like, many of these herbs are forced to retreat indoors over winter. If there is a relatively little culture shock in adjusting to our summers, there is relatively more in bringing these herbal treasures indoors. The main problem is the lack of light. But despite lighting conditions often less than one tenth the intensity and duration of the outdoors, herbs can be grown indoors successfully year round and many herb enthusiasts in Toronto do so.

Most herbs will grow well in any east, south or west window that receives at least four hours of direct sunshine a day. Artificial grow-lights are useful to supplement natural light (say in a north-facing window) but they by themselves do not provide enough light of grow herbs with enough vigor to satisfy a cook’s demands.

Planter Box

A simple growing system that works well for most of the popular herbs is the windowsill planter box method. The planter box may be plastic or wooden, approximately 15 centimetres wide, 15 centimetres deep, and 1 metre long (6 by 6 inches by 3 feet) and should fit the intended window so that the plants are as close as possible to the available light. Pieces of charcoal broken into 1-centimeter (1/2 inch) pieces are placed in a 2 centimetre (1 inch) layer at the bottom. Charcoal tends to prevent the soil from going sour, especially if there are not drain holes in the planter. On top of the charcoal is placed 5 centimetres (2 inches) of sterilized potting soil. Herbs potted in plastic or clay pots are then placed firmly on this soil layer and then more soil is packed down in the space between the post and the walls of the box. Do not remove the pots; plant pot and all. About six herbs will fit in a 1-metre long box, leaving space between each pot. The soil level should be slightly lower than the rim of the pots, which in turn should be about 1 centimetre (1/2 inch) below the rim of the box.

This simple planting system has several important features. First, individual herbs can be removed, repotted or replaced, as necessary, without disturbing the rest of the herbs in the planter. Second, the extra soil around the pots allows the roots to penetrate new soil when they otherwise would have exhausted the soil of a stand-alone pot. Third, with careful watering, the herbs will be happy even if you decide not to punch holes in the planter box for fear of water dripping over furniture and floors. On the third point, however, it is always better to have holes on the bottom and allow the water to drain out of the planter.

This system works well with most of the herbs listed below. With minimum care, a planter will flourish for a year or two, before needing a complete overhaul. If the potting soil used is a good compost mix with well-rotted manure mixed in, then little fertilizer will be necessary. A liquid fertilizer high in nitrogen (the first number in the analysis) can be applied every four to six months if hunger signs (yellowing) develop.

During the summer you will notice faster and healthier growth if you move the planter outdoors. If you do, expose the herbs gradually over several weeks to the stronger light to allow them time to adjust. You will also need to water more often. When you bring the plants back in the fall, you will again need to adjust the plants to the changed light condition. This time, expose them gradually to the lower light.

Contrary to popular belief, herbs are susceptible to pests despite their natural biochemical arsenal. This is especially true (for reasons not yet fully understood) when herbs are grown indoors. A good practice is to check for whiteflies, spider mites, etc. regularly and apply an insecticidal soap if necessary.

Here are some of the more popular indoor herbs:

Basil: The lord of pesto and everything tomato actually comes in more than a dozen varieties with varying size, colour and scent. Among the more exotic are the anise, lemon and cinnamon scented strains, but most Torontonian herb lovers are already married to that known as "sweet basil" in either the diminutive Italian bush or regular large leaf forms. Bush basil has a lovely dwarf, compact habit well suited for pot culture. Most varieties will grow quite happily indoors, but as annuals, they wear out after four to six months and need to be replaced. Starts easily from seeds or available in plants form.

Chives: Welcome inhabitants of kitchen gardens, these, the most delicate members of the onion family, offer great improvement to salads, soups, vegetables, omelettes and cheese dishes. There are two kinds: the regular onion chives with hollow leaves and mild onion flavour, and the irresistible garlic chives variety with flat leaves. Both are easily started from seeds or available in plant form.

Coriander: Regular coriander (also known as cilantro or Chinese parsley) is best grown from seeds; don’t buy plants, unless you are buying the less common Vietnamese coriander, which has the same flavour but entirely different (oblong) leaves. Regular coriander must be sown in three or four pots a week apart in rotation in order to ensure a constant supply of fresh leaves. Do not transplant, just snip stems when large enough. Once snipped, they don’t grow back, so a new pot must be sown to replace the old one. The Vietnamese variety, on the other hand, regrows continuously from the same pot.

Mints: No green thumbs required here. The mints make few demands, growing happily even in the indirect light of a north facing window. Their only demands are occasional pruning and repotting to control their aggressive habit and to replace exhausted soil. There are dozens of varieties, the most popular of which are the venerable spearmint and peppermint. My favourite for indoor growing is english mint because it has sturdy compact growth habit and a versatile flavour. Do not try to start mints from seeds because the result will have little culinary value.

Oregano: There are many kinds of oregano, good and bad; buy only plants whose leaves burst out with he familiar oregano odour when squeezed. Can also be grown from seeds, but it is difficult to know what you are getting because some seed companies sell strains almost completely lacking in flavour and odor. Greek oregano is highly recommended.

Parsley: Fresh parsley is so widely available in markets year round that it could be omitted from the indoor herb garden. It never seems to thrive in pots as well as it does outdoors anyway. However, outdoor-grown plants can be dug up and potted in large pots or tubs in autumn for an extended season indoors. If undamaged in the digging process, the large tap root usually has enough food stored to carry the plant for several months. The familiar curled leaf is popular for flavouring and garnishing, but those in the know prefer the flat-leaf Italian variety, which is stronger in flavour. Start from seeds or purchase plants.

Rosemary: Fresh rosemary has many unexpected used in the kitchen. Rosemary is best acquired in plant form as the seeds are slow to germinate. Give rosemary your brightest window.

Tarragon: Its distinctive anise or licorice-like flavour is deeply satisfying to the palate. Since only the fresh leaves possess flavour, it is essential to establish one’s own fresh supply. Buy only true French tarragon plants after applying the squeeze-and-smell test. Indoors, tarragon will succeed in a bright window for most of the year; however, it can languish during the winter months unless it gets a cold treatment.

Thyme: The culinary thymes (as distinct from the ornamental thymes) come in several forms, including three common English and French varieties, an attractive silver form, and the lemon, caraway and nutmeg-scented thymes. English and French can be grown from seeds or plants purchased. The others are available in plant form only.

Originally published in The Toronto Star, March 29, 1988.

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