Summer’s over but they can still grow indoors
In this reprint of an article from October 1997, landscape architect Bardi Vorster helps us identify which herbs we can bring indoors and enjoy long after the first frost.
By Bardi Vorster
The first task when you mention herbs is to narrow the field. The ones we are talking about here are all edible — hence the term pot herb. There are often several uses for one plant; ancient remedies claim everything from medicinal cures to voodoo, but this is a gardening article so I will concentrate on growing them — successfully — indoors in winter.
What they really like
Of the many popular cooking herbs available, the following are some of the easiest to grow. As a group they are generally less demanding in soil types, although all absolutely require a well-drained mixture. Soils of slightly acid or neutral pH are best; don’t use the rhododendron fertilizer on them! It’s acid.
For rosemary, thyme, lavender, and oregano, try some crushed egg shells as a mulch. They are calcium sweet. It is also a common trait that herbs prefer soils which are not too rich. This means a lower organic content, so combining some “cactus mix” with the regular potting mix will at least ensure fast drainage.
When you consider that virtually all of these are native to Mediterranean climates, you can surmise that the biggest problem is the quantity and quality of light. Most herbs need full sun (four hours a day), so give them all you’ve got.
Although parsley, rosemary, mint, and oregano will tolerate some shade, indoors they do better with more light. Given the natural light levels in Toronto in the average winter, your plants will be virtually dormant or growing very slowly. Additional fluorescent light will help.
If you only have north light, face the fact that even the hardiest herbs will languish. Don’t forget to rotate the pot occasionally to keep them growing straight.
I’ve found that the best survival strategy for herbs indoors is to buy or transplant the biggest plant you have. Larger plants withstand variations in temperature and watering better and, of course, there is more to clip and eat. Although most herbs are easily grown from seed, now is not a good time to start. Grocery stores and garden centres offer plants at various seasons and at this time of year the St. Lawrence Market has larger specimens.
Water, fertilizer, and air
Don’t water your herbs on a regular schedule but rather as they need it. In fact, keep them on the dry side. Use room temperature water to avoid shocking them and be sure that they do not stand in water. Never let your rosemary dry out completely; it dies, seemingly overnight. Furthermore, appearances are deceiving, I cheerfully watered mine for a month before I realized it was absolutely dead!
As the plants are not growing very fast don’t overdo the fertilizer. Fish emulsion is gentle or 20-20-20 applied every month will keep them going. Good air circulation is healthy for plants and people and similarly drafts are not. It is best not to move the plants around, so they won’t have to adjust all the time.
If you are bringing plants inside from the garden, you should do so before the heat goes on. Acclimatize them in a shaded location for a couple of weeks. Examine them carefully for insect visitors and spray with insecticidal soap if necessary. Chives can be left outside until the frost kills the foliage. Trim back to 1.5? when you bring them in and soon new growth will spring up.
The following best-for-indoors culinary herbs have been selected for similar growing requirements and smaller size. They are all happy with daytime temperatures in the 70s and a night temperature above 40 degrees.
Chives: Allium schoenoprasum. Will be happy in a pot for years and the bulbils are easily divided if it gets overcrowded.
Lavender: Lavandula angustifolia. All parts are fragrant and it is much used in cosmetics. It is an uncommon flavour for food but the flowers are edible — lavender ice cream anyone?
Mint: Menta piperata (peppermint). There are many different flavours of mint; all of the plants are vigorous growers and should be productive in pots for six months or more.
Parsley: Petroselinum crispum. Harvest by cutting the outer leaves, leaving the central rosette to produce new growth.
Rosemary: Rosmarinus officinalis. An attractive evergreen shrub. The leaves are used to repel moths as well as to eat. Misting the branches is beneficial. Be especially vigilant about watering, but don’t overdo it.
Sage: Salvia officinalis. Replace the plants when they become woody as they are not as productive.
Marjoram: Origanum majorana. Keeps its flavour when dried but keep out of direct light to preserve colour and flavour.
Oregano: Origanum vulgare. The strongest flavoured one is Greek; however plants can vary considerably so you should taste before you buy.
Bardi Vorster is a practising landscape architect in the Kingston area. Her website is www.individuallandscapes.com/ and her email is email@example.com.