Well Being

Green Thumb Guide: How To Keep Your Basil Plants Alive

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Last week, I brought you basil recipes to help you take advantage of abundant summer crops. But many of our Facebook fans balked; basil is a tricky herb to grow. Unlike some herbs (I'm looking at you, rosemary), it's easy to start from seed. But keeping it alive? Oof. Not so simple. I bought a tall, lovely basil plant about two weeks ago—you were right: this week, it's dropping leaves faster than the temperature is rising, and what's left is quickly becoming flecked with holes and brown spots. So what gives? I asked gardening guru Kimberly Sevilla (co-owner of Brooklyn's Rose Red & Lavender floral and garden shop) for advice.

The secret to maintaining healthy basil plants, indoor or out, is water, heat and a nitrogen-rich fertilizer, says Sevilla.

If you're growing basil indoors you need to make sure it gets enough light (basil loves sun; five or more hours of direct sunlight a day is best). And you may want to use fans to keep the air around the basil moving. That will help prevent fungus and gnats, which can be a big problem with basil. “Make sure you clean up any leaves that fall on the soil, because these will grow fungus and mildew very quickly,” Sevilla notes.

Water: Keep the basil moist. You don't want to let the soil get to dry—but you also want to let it dry slightly between watering. Make sure you use a container where it can drain properly. According to the Herb Society of America, in general you want to water “when the soil begins to lighten or become flaky,” though watering needs will vary depending on your climate.

Fertilizer: Sevilla recommends using worm castings or Happy Frog Fertilizer's all-purpose blend. “If my basil leaves start looking pale green or yellow,” she adds, “I spray them with Neptune's Seaweed plant food, which is called a foliar feed and works wonders for the plant.”

Pruning: Nip flowers in the bud, literally. Once basil starts flowering, the taste becomes a little too strong, says Sevilla; pinch off any flower buds that form as soon as you see them.

You should prune your basil fairly often to keep the plant healthy and robust. The Herb Society recommends doing it every 3-4 weeks (pruning doesn't refer to just removing leaves to use, but cutting the plant back to 1/3 of its size—about the lowest 2-4 sets of leaves).

What's the best way to pick basil for use? DIY Life says:

For pick-as-you-need-it freshness, choose the succulent leaf clusters at the tips. Be warned, however, that if you routinely pinch off all the leaf clusters, the plant may respond by sprouting flowers simultaneously with the new leaves. The best approach is occasional tip pinching, followed by regular harvesting.

Pests: If you're growing basil outside, you've got a few added menaces to contend with. “Slugs love basil as much as we do,” Sevilla notes—but you can keep them away by keeping pots elevated; putting copper slug tape around the pot's rim; or placing trays of beer around your plant to attract and drown the slugs (apparently, slugs love beer as much as they love basil). “Caterpillars also love basil; these you can pick off and move, or destroy (depending on your mood).”

So what's with my basil shedding and spotting problems?

“Sounds like it is getting too much water and may have a fungus,” says Sevilla. “Trim off the affected leaves and spray your basil with an organic fungicide, or wipe the leaves with neem oil,  or even try a spray of baking soda and water. Keep a fan near your basil, the air circulation will be good for it.”

Photo: Paul Goyette