Heading into fall, you might be dreading cold weather and the loss of fresh cut herbs in meals. The dried versions simply don’t give you the same flavor, and some, like cilantro have no flavor at all in this form. It isn’t really difficult to grow herbs inside. Most of them are perfectly happy indoors if you meet their most important needs.
The two most critical things you need to succeed at container growing herbs indoors is good light and moisture control. I see a lot of bloggers and YouTube channel owners showing people herbs growing on windowsills in disposable containers, mason jars and tea cups. There is no drainage here, and most people will kill their herb plants fast using this kind of container. Don’t use containers with no holes in the bottom. If it comes without them, cut or drill through the bottom to create the right root environment.
Getting the Right Root Environment
All plants need some moisture on their roots, but never do well submersed in standing water. They can’t breathe this way, and yes, plants need oxygen at their roots. Some plants, those that thrive in dry situations, which most herbs do, will quickly develop root diseases when the soil never dries out. In an indoor container, both of these high moisture situations are amplified, as is the effect of drought. A house is a dry climate to begin with. There’s no dew, no mist, and no rain to replenish moisture at the roots – nor is there any breeze to help get rid of excess moisture.
Little clay pots are cute, but they will make keeping soil moisture present difficult. This is especially true as the temperature outdoors drops in winter, and your heat kicks on more often around the clock. Clay containers allow dry air in through the sides, which rapidly removes all moisture from the potting mix. It’s pretty easy to kill herbs indoors growing them in clay pots over the winter. You’ll be farther ahead with ceramic or plastic pots that have good drainage holes in the bottom. This helps to keep the potting mix moist longer, while still allowing much needed oxygen to the root systems.
Worried about the pots making a mess? Putting a piece of coffee filter in the bottom will let liquid get out, but stops the potting mix from escaping. There will be far less run-off if you let the pots sit in the sink for 10-15 minutes after watering the containers. Catch the rest by putting a plate or something under it. Don’t water again with excess sitting in the tray or plate – empty it first.
Once you’ve got good drainage and moisture retention capabilities, you need to remember to check the growing medium moisture regularly. Stick your finger in it. If its dry beneath the surface, you need to water. If it’s still moist, make it a point to check it again day after tomorrow. Of course, if you forget your herbs will start signaling they need water by drooping or developing yellow leaves, but not all herbs droop. Thyme and rosemary have woody stems with fine leaves that stay stiff even when they’re dead.
The Importance of Light
All herbs are sun lovers. They don’t do very well in low light situations. In every image where people have an herb garden in the kitchen window it’s summertime – the trees are full of green leaves outside and lawns are green. The sun is drastically different from late fall through early spring, and your plants will behave like it too.
While you get the most sun through a south facing window, the sun needs to be shining more than hidden behind heavy cloud cover. Winter in the north usually means very little days without cloud cover. Container growing herbs using sunlight alone from about mid-December through February could prove impossible in some locations, because the days are too short and dreary. The solution is to supplement the available sunlight with grow lighting.
An east facing window will also not have enough light. A west window is better, but your herb plants will still get leggy and lean for the sun. Why? Because they need more energy and they’re desperately trying to find it. Without enough sun hours or intensity of it’s light, plants can’t manufacture enough food to be robust. This will not give you a steady supply of fresh herbs to cook with. If your plants are weak and spindly, go out an buy them some temporary sunshine. They’ll thank you for it by giving you fresh herbs to cut regularly. Small high output T5 fluorescent lights aren’t that expensive, are very economical to run and will allow you to grow herbs indoors through the winter.
If you don't find her at the desk - check the gardens. When not writing and weeding, she enjoys a good book, painting junk furniture, and blending the harvest of heirloom tomatoes and chiles into salsas.