by Jill Henderson – Show Me Oz –
Now that summer has come to an end and the cool sunny days of fall are upon us, it is time to think about preparing the garden for a long winter’s nap. It is the perfect time to divide and transplant perennial herbs. But while your at it, why not bring some of that summer sunshine indoors for the winter? Many herbs growing outdoors can be brought indoors for the winter, providing much needed freshness to both the windowsill and the cooking pot.
Whether you want to bring in a small division of mature perennial herbs such as sage or rosemary, or some new seedlings of annual herbs like basil and parsley, the first step is to ready those plants for life indoors. Start by selecting sturdy plastic or glazed pottery pots in which to grow your herbs – unglazed terracotta pots tend to dry out too quickly. Because plants don’t stop growing when brought indoors, it is crucial to select pots that will allow plenty of room for new root growth.
One of the most important steps to in preparing potted herbs for life indoors is a process akin to the spring ritual of hardening off, but in reverse. Rather than acclimating herbs to more and more sunlight as is done with seedlings, herbs to be moved indoors need to be acclimated to less and less light if they are to thrive in the relatively low-light conditions inside your home.
Leaves use sunlight to generate food essential for a plants’ survival. To do this in the most efficient manner, many plants produce specific leaf shapes in order to capture various levels of light. For example, in response to very bright sunlight plants will often generate long, thick and narrow “high-light” leaves. These are leaves that receive abundant sunlight and do not need to be as efficient at producing food. On the other hand, “low-light” leaves are thinner and wider in order to make the most food possible with less sunlight. Therefore, when the intensity of light is suddenly reduced – as is the case in winter or indoors – plants must respond by growing more low-light leaves. If they cannot produce these new leaves quickly enough, they will either flounder in the struggle to produce enough food or die.
Rosemary is notorious for being difficult to grow indoors and the biggest contributing factor to this is its inability to respond quickly to changes in light intensity. Therefore, to prevent low-light shock, pot up herbs like rosemary as much as six weeks before the first frost in your area and move them to shadier and shadier locations in two-week increments. I call this reverse hardening. During this adjustment period, herbs will have time to grow many new low-light leaves and when given a bright windowsill indoors, will burst with new growth .
Indoor plants need water only when the soil is almost but not quite dry. This may be once a week or once every several days depending on relative humidity, growth rate, and type of soil used. Ideal soil moisture feels like a well-wrung sponge to the touch. Don’t rely on the feel of surface soil – it often “feels” dry. A moisture meter is an easy and accurate way to test for moisture down in the root zone. If you don’t have a water meter, probe into the soil with your finger about an inch deep. This will allow you to get a truer picture of soil moisture where it matters – at the roots.
A deep watering once every seven to ten days is usually sufficient for indoor plants. Water deeply and thoroughly until the water runs out of the bottom of the pot. If you have saucers underneath your pots, be sure to drain them after about thirty minutes. Standing water may lead to root rot, mold and other diseases.
Plants growing in dry, indoor air welcome humidity. Create a moister environment for your plants by placing them on shallow trays filled with smooth pea gravel. Add water until it is just below the surface of the gravel. Renew the water as needed. If you grow herbs on gravel trays, you can forgo the saucers under the pots and let the water that runs from the drainage holes renew the water in the trays. Otherwise a small humidifier can be placed near the plants and used regularly to combat dry indoor conditions common during the winter months.
I have talked to gardeners who swear by showering their indoor plants once a month in the bathtub. A good 5 to 10 minute shower of lukewarm water should do the trick. After their “rain” treatment, the plants are allowed to drain for several hours before being put back on their stands. This procedure accomplishes several things. First, it gives the plants a deep and thorough watering, which helps remove toxic salts excreted by the plant from the soil. Second, it rinses dust from the foliage, allowing more light to reach food producing plant cells. Last but not least, it creates a penetrating humidity that stimulates leaves to uptake moisture and nutrients. This is an excellent time to apply a light foliar feeding of liquid kelp to all your herbs.
I hope these tips and tricks help you grow a better indoor herb garden. Learn more about growing herbs in my book, The Healing Power of Kitchen Herbs available in the Show Me Oz bookstore.