How To Grow An Indoor Herb Garden
One of summer’s simple pleasures is picking and using fresh herbs from the garden. But just because the days are getting shorter and temperatures cooler, doesn’t mean this has to end. You can bring herbs from your garden inside as well as start an indoor herb garden if you don’t already have one outdoors.
Herbs You Can Grow Indoors
Some herbs are better suited to indoor living than others. Easy-to-grow indoor herbs include basil, rosemary, chives, parsley, mint, oregano, sage and thyme. Some general tips about growing herbs indoors is ensuring herbs get enough light – they’ll need 6-8 hours per day, either natural light through a southern or western facing window and/or supplementation from artificial light such as a grow light. (Note: a regular table lamp will not provide sufficient illumination).
Growing Conditions for Indoor Herbs
Keep them in rooms that are at least 65-75°F during the day, and no less than 55-60°F at night. They’ll survive at lower temperatures but won’t grow much under cooler conditions.
Good drainage, minimal fertilizing with a balanced fertilizer, ample light and a draft-free location are a recipe for success for growing herbs indoors.
A rule of thumb is that herbs native to the Mediterranean do best by a south-facing window in the winter. These include basil, rosemary, sage, oregano and thyme. Herbs such as chives, parsley and mint that like it a little cooler can survive in a west-facing window in winter. If you plan on keeping your herbs inside year-round, note you will have to move your plants from a south-facing window in the summer, when the light will be much more intense.
Keeping your plants by a southern or western facing window, doesn’t necessarily mean on the actual windowsill itself. Particularly if the windowsill is narrow and the plant winds up touching the windowpane, it’s likely the plants can be subjected to cold drafts which can be damaging. It’s better to have them on a table or stand near a window, away from drafts.
Making the Transition from Outdoors to Indoors
For herbs you’ll be transplanting from your garden to the indoors, it’s important to allow for a transition period, keeping the plants in a shaded outdoor area for a few weeks before bringing them inside. Timing is important since you don’t want the plants subjected to a hard freeze before being brought indoors. Additionally, check for pests before bringing your plants inside.
Plant-Specific Growing Tips for Herbs
Here are some plant-specific tips for caring for herbs indoors:
You can dig up your basil plant from your outdoor garden or grow new plants from cuttings. If you’re potting your plant from your outdoor garden, make sure to use a large deep pot. Basil can be prone to fungal diseases which can be prevented with good air circulation. It’s also helpful to water basil from the bottom – not overhead – keeping the soil damp; neither too wet nor dry.
If you opt to grow basil from cuttings, you can either put cuttings directly into pots with a potting soil mix or place them in water to root first. You can actually let basil grow in water permanently by mixing a gram of a balanced fertilizer (N-P-K, 20-20-20) with a liter of water and use this as a growing medium. Basil will do best placed by a south-facing window.
Make sure you bring rosemary indoors well before the first frost. You’ll want to keep it in a warm room free from drafts and away from drying heating vents. While it does well with a bit less water than some other herbs, don’t let it dry out completely before watering. In fact, rosemary needs more humidity than other herbs – not more water.
In the dry heat of our homes in the winter, humidity can be hard to achieve, so consider tenting your rosemary to trap in moisture. Place a few sticks in the pot and drape clear plastic over the stakes to form a tent.
Rosemary will benefit from a full 6-8 hours of sunlight from a south facing window, and perhaps some additional light from a grow light.
Chives multiply over time, so if you have a good-sized mass in your outdoor garden, it’s healthy to divide them. When you dig them up, you’ll see tiny bulbs and a mass of roots. Gently break off a clump (or several clumps) and transplant these to a pot.
Chives’ light needs aren’t as intense as some other herbs, so you can opt for a west-facing window for sufficient light during the winter.
Oregano loves light, so err on the side of giving it more light than you think it may need in winter. This includes 6-8 hours of sunlight from a south-facing window but may also include additional light from a grow light.
Although it’s not as humidity-needy as rosemary, oregano does better with a bit more humidity than the average dry-heated home provides. Placing your pot of rosemary on a dish filled with moistened pebbles will provide sufficient humidity for your oregano.
Parsley has a long tap root that doesn’t like to be moved, so it’s best to start your indoor parsley by seed, sowing them directly into high quality potting soil in containers. Parsley likes slightly cooler temperatures, so it can survive in a west-facing window in the winter. It likes soil that is evenly moist, with good drainage, but not so porous that water drains through immediately. Like oregano, giving it a bit more humidity by placing the pot on moistened pebbles will help it thrive.
Sage needs a lot of light, so along with keeping it by a south-facing window, consider getting a grow light to supplement its lighting needs. Water plant containers when the soil is dry to the touch – sage doesn’t like soggy roots. Avoid getting water on the foliage when watering the plants. Try to water only the soil and maintain good air circulation to lower the incidence of powdery mildew.
Mint thrives in somewhat less intense heat and light than some other herbs, It likes its soil to be kept evenly moist, but not soggy. Mint is an extremely aggressive grower outdoors, so there’s a real advantage to growing it in pots, both indoors and outside. Mint will do well in a west-facing window in the winter, needs minimal fertilization and benefits from good drainage.
Thyme is the opposite of rosemary in one respect: It likes low humidity. So save the windowsill in the kitchen (a room that tends to be more humid than most) for your rosemary and find a sunny windowsill in a drier room for your thyme. Thyme is drought-tolerant and can actually be harmed if it gets too much water. It needs excellent drainage, a south-facing window and minimal fertilization to thrive.
Most herbs require at least 6 hours of direct sunlight, and it doesn’t hurt to put them under a grow light. The exceptions to this rule are mint, parsley and rosemary, which can take a little less light. Use light bulbs between 4000 and 6000 Kelvin, as the bulb’s color temperature will borrow from a full spectrum of colors—cools and warms. With these lights, you can actually mimic the growth you would get in a greenhouse or outdoors. Standard LED lights only provide illumination while LED grow lights have a wider spectrum of both blue and red light that promote vegetative growth and flowering,
Good full-spectrum lights for indoor gardening have a CRI rating above 85, but the closer to 100, the better. Be sure to buy enough fixtures to evenly distribute the light over the entire area. Violet-blue light in the 400 – 520 nanometer range is considered an ideal color for plant growth, encouraging chlorophyll absorption, photosynthesis, and overall growth.
Grow Light Color and Plant Growth
Botanists have gained a solid understanding of how plants use different color spectrum components during their growth cycles. The following generalizations hold true in large part for most plants:
- Blue light is an essential part of a plant’s germination phase. Concentrations of blue light encourage sprouting and strong root development.
- Violet or purple light has a shorter wavelength and higher energy. It’s regarded as an effective secondary light source to facilitate growth and development of a plant’s leafy vegetation.
- Green light is typically reflected away from plants (which is why they appear green), but plants absorb small amounts of green light throughout the photosynthesis process.
- Yellow and white light have the lowest effect on plant growth.
- Red light impacts plant growth during the blooming and flowering phases. Certain specific red wavelengths increase the production of a hormone in a plant’s vegetation that prevents the breakdown of chlorophyll. With more chlorophyll, a plant generates more nutrients and grows taller with more leafy vegetation.