INDOOR HERB GROWING TIPS
Light is the most important aspect of growing indoor herbs, and many people don’t have enough. Most experts agree that six to eight hours of light per day is optimal.
Orientation: A southwestern-facing window is your best bet for good light, says Diane Stahl, owner of Urban Roots, a Denver-based city garden store and greenscape installation company specializing in small urban spaces.
If you can’t get light from the sun: Get a few clamp-on reflector lights with compact fluorescent bulbs, says Rose Marie Nichols McGee. Connie Campbell says the lights should be placed very close to the plants, about four to six inches away. There are also light fixtures that mount under a kitchen cabinet if you want to have herbs on the counter. The bottom line is, no plant will thrive if you can’t give it enough light.
If you see brown spots on the foliage: “It can be a sign they are burning,” says McGee. That means the plants are getting too much light, but this is a rare scenario.
If the plants are growing longer stems and fewer leaves: They’re not getting enough light and are stretching to find more. Add supplemental light or move them to a place that receives more natural light.
Herbs don’t need that much water. “Overwatering is the biggest mistake people make trying to grow herbs inside,” says John Lingle, owner of Lingle’s Herbs, a nursery specializing in organic herbs located in Long Beach, California.
When to water: You need to learn to read your plants and let them tell you when they’re ready for water. “The rule of thumb is to let all the herbs dry out completely,” says Urban Roots’ Stahl. It could take anywhere from a few days to well over a week before you need to water. “Put the index finger in the dirt all the way down to the knuckle and feel that root system,” says Stahl. Write down how long it takes for the plants to dry out, then try to develop a consistent watering system. Stahl says that though plants don’t like a lot of water, they do like consistent watering.
How to water: Put the plants in the sink and water the base where the stem meets the dirt, not the leaves; let the water soak through. Then soak the plants again. Let them drain completely and put them back in their saucers. You can water in the morning and let the plants drain while you’re at work. Never leave standing water in the saucer or you’ll rot the plant’s roots.
If the leaves are yellow: The first assumption you should make is that the plant has too much water, rather than too little. When a plant is too wet, the roots rot, leaving them less capable of taking up water. “It’s kind of a Catch-22, because when the roots start to rot, the plant desiccates and wilts, so people think it needs more water,” explains Lingle. Feel the soil and lift the container to see if the plant is very wet or dry.
Rule number one: Your pots must have drainage holes.
What material to use: Terra cotta, because it breathes. The saucer material is not as important, since its main purpose is to protect your counter or window sill. And forget about putting rocks in the bottom of the pot before you add soil: McGee says that will actually clog things up instead of promoting better drainage.
The best size: Bigger is better. For individual herbs, the pots should be no smaller than 6 inches in diameter. To grow multiple herbs together, you’ll want to put two or three in a pot that is about 10 inches in diameter and about 8 inches deep.
High-quality organic potting soil with good drainage is a must, and it should be rich, loamy, and not compacted. You can add perlite (buy it at any garden store) to increase drainage; Connie Campbell says a ratio of 1 part perlite to 25 parts soil is good. Don’t just take a shovel of dirt from outside and put it in a pot, she warns. “You’ll bring in all the organisms that are balanced by nature but won’t be under indoor growing conditions.”
How to judge drainage: New American Garden author Carole Ottesen says, “It [shouldn’t] lump together in a ball if it’s wet—it would always be grainy. If you squeeze it and it doesn’t stick together and it sort of crumbles, that’s good.”
Add eggshells: Rose Marie Nichols McGee says that Mediterranean plants like rosemary, thyme, and basil do well with a little extra lime; you can use eggshells for this. “I suggest they put the shells into a food processor with a little water and put a spoonful into each pot when you prep the soil for planting.”
Herbs are fairly hearty, but they still like to be fed a good organic fertilizer like fish emulsion (be aware: it stinks) or liquid seaweed. You’re growing herbs for their leaves, not their flowers, so find a fertilizer that doesn’t promote blooming. That means the fertilizer needs to have a low level of phosphorous. John Lingle suggests getting a gallon apple-juice jug and filling it with water and one tablespoon of fish emulsion to make a very weak organic fertilizer solution. Water the herbs with it, and then you won’t have to worry about when to feed them.
Do what the plants tell you: The plants will let you know if they need to be fed, says Carole Ottesen. If they seem to have stopped growing, they probably need food. If the plants are turning yellow and you’ve already ruled out watering issues, this may also mean they need feeding.
Buy plant “starts” (baby plants), not seeds—growing from seeds is harder. When you’re buying plants to grow indoors, buy an herb that’s never been planted outside; changing the environment can be traumatic for the plant. And as Diane Stahl points out, “If you shop locally, you find plants acclimated to your area.” Which can make it a lot easier on a new gardener.
Is this my best side? Rotate your pots every week, says McGee. “Don’t just leave them in the same position forever. Move them around so they don’t lean.”
They’re there to be eaten: Cutting your herbs encourages growth. But don’t cut more than a third off.
You’re not growing fungus: Herbs need good air circulation, says Stahl—stagnant air promotes fungal disease. You can combat this by putting your pots on a large tray covered in pebbles so that air can circulate up through the drainage holes.
Don’t try to fight nature: In the winter, plants may naturally be in a resting phase because of the changes in light, says McGee. “We can let plants be in a resting phase. Minimally water; just let them do what they do.”
Pest inspection: If you see aphids, rinse them off in the sink. If you see scale (it looks like a brown, rusty spot), wash it off with a mild soap or rub off each spot with a little bit of rubbing alcohol, and then rinse the plant.
Go back to the roots: Check potted perennials about once a year to be sure the roots aren’t growing out of the bottom of the pot. If they are, take the plant out of the pot and inspect the roots: They should be healthy and white, not brown and growing around in a circle. If the roots look bad, you have two options: Trim off a little bit and transfer the plant to a bigger pot. Or, if the plant is the size you want, McGee says, you can just cut around the roots vertically, about a half inch to an inch, and slice the same amount off the bottom. Repot with extra soil, and take off about the same amount of upper growth as you removed from the roots.
Contact master gardeners in your area; they are experts who volunteer time to run hot lines and answer questions via email about local agriculture. Your local USDA Cooperative Extension office can help you find one in your area.
Also talk to people at your local nurseries who know your climate (not the folks at the big-box garden supply counter).
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