Don’t water at night and other secrets to growing great basil
Few things spice up a dish – or, for that matter, an herb garden – like basil. With flavor profiles that include sweet, spicy and even citrusy, the herbaceous staple is a favorite of both growers and chefs.
“Think of a perfectly rich basil pesto, or a topping that turns a pizza into an absolute conversation piece,” said Jekka McVicar, a U.K.-based herb grower and vice president of the Royal Horticultural Society. “Basil is the flavor and fragrance of the summer. Even the scent of it is evocative; there’s nothing better on a warm night than sitting next to a big basil plant.”
As an added bonus, it’ll keep the bugs away. “It’s one of the best mosquito repellents,” McVicar said. “I even rub my skin with it.”
But basil can also be a bit fickle. Here, experts offer tips to help you grow better basil – plus some ideas for how to enjoy it.
What basil needs to thrive
Though many people associate basil with Italian, Greek and other Mediterranean cuisines, it’s a tropical plant, native to India and Southeast Asia. That means that it needs sunshine and warmth more than anything else.
“In the U.K., we really can’t grow it in the ground. The soil is too cold,” McVicar said. “But we can do it in pots, and in much of America, it’s fine to grow in the ground.”
If you’re starting plants from seed (either indoors or outdoors) or transplanting seedlings from a nursery, McVicar’s biggest piece of advice is patience: “Don’t plant too early. I really mean that,” she said. “Wait until at least May, when it’s warm overnight and the light levels are good.”
A good rule of thumb? “When you can sit on the soil without your knickers on, then it’s warm enough to sow basil outside,” McVicar said.
In addition to warmth (and plenty of water; more on that in a moment), basil needs nutrients. McVicar said any basic vegetable and herb fertilizer will work, as long as you’re consistent with feedings. “I feed on Fridays with liquid seaweed,” she said. “It’s like you taking a regular multivitamin: you’ll be amazed at how your plants respond. They get strong and vigorous and give you enough to cut.”
How to prune basil and cultivate cuttings
Once your basil plants are established, they need regular harvesting to continue that vigorous growth. “Always pick from the top,” McVicar said. Pinch off the top few sets of leaves until you see a place where tiny buds or leaves have formed at the junction of a leaf and stem. Cut it back to that point, and two new branches should grow on either side.
The best way to make the most of your basil season is to help your plants multiply. Cuttings from a healthy plant will root in water or potting mix in a week or so. “What you do is cut a branch with a growing tip, and maybe three leaves on either side,” McVicar said. Trim the leaves below the growing tip, then put it in a few inches of water or plant it in a small cup with potting soil.
Once roots form, move the new seedlings into larger pots or plant them right in the garden. This is also a great trick, McVicar said, for turning one grocery store plant into a whole basil crop.
How to keep mildew at bay
The plant’s susceptibility to certain diseases and pathogens can make basil difficult to grow. One of the most common issues is a fungal disease called basil downy mildew, which turns the plant’s leaves yellow or dark and mottled.
“It was first discovered in Uganda in the 1930s, and then rediscovered in Europe around 2001,” said C. Andrew Wyenandt, a vegetable pathologist at Rutgers University who has been breeding basil plants for more than 15 years.
In 2007, basil downy mildew was identified in crops in Florida. “It was the first time it made its way to the United States, probably shipped in on contaminated seed,” Wyenandt said. “For a few years, it pretty much wiped out 100% of the basil crop in the Eastern U.S. because none of the sweet basil varieties had any resistance.”
A breeding program at Rutgers has since produced four sweet basil varieties with high resistance to the fungus. The cultivars – Rutgers Devotion, Rutgers Obsession, Rutgers Passion and Rutgers Thunderstruck – are now widely available at nurseries.
There are also ways to lower the risk of developing a basil downy mildew problem, regardless of the variety you plant. The first, Wyenandt said, is vigilance. Growers “should inspect their plants on a regular basis,” he said. “If you’re buying basil at the local garden center, you should inspect the leaves and see if there’s any yellowing. Look on the underside of leaves for purplish brown spores.”
Pass up those plants at the store. And if you do see signs of the fungus on your plants once they’re home, remove those leaves – -or even the whole plant – right away to try to keep the rest of the basil healthy.
The best way to water basil
Though basil – being a tropical plant – does need a lot of water, McVicar said many people make the mistake of watering too often, or watering incorrectly. “All of us want to nurture our plants, so we overwater,” she said. It’s important to allow the soil around your plants to get mostly dry before watering deeply again, she said.
Even more important is when you water basil. “Water in the morning, never at night,” she said. “At night, especially in the spring, you have fluctuating temperatures. If you water before you go to work, rather than when you come home, you don’t send basil to bed wet.”
Watering earlier in the day ensures any water that does fall on the leaves will dry quickly. It’s also helpful, Wyenandt said, “to plant basil in a sunny location with adequate spacing between plants. Air circulation is very important.”
Keeping the plant’s leaves and stems as dry as possible also helps control fungus. “Don’t water the top of the plant,” Wyenandt said. “Instead, water the soil beneath the plant. Humidity and leaf wetness is important to the development of disease.”
How to use basil in the kitchen
Whether you’re growing sweet, Thai or cinnamon basil, or another variety, the flavors will be best while the plant is actively growing and putting energy into its leaves.
“The most important thing with basil is you don’t want it to go to seed,” Wyenandt said. “If you allow it to produce flowers, it’ll put off the chemistry of the plant, which will affect the flavor.”
If a plant does bloom, though, that doesn’t mean it’s no longer edible. “Yes, it does change the leaves, and they become slightly tougher. But eat the flowers,” McVicar said. “You will be stunned by the flavor: lemon basil flowers, especially, are sublime.”
And there are plenty of ways to use the herb, beyond the obvious applications (such as in pasta dishes and Caprese salads). “I chop up lemon basil and mix with olive oil and white wine vinegar for the best salad dressing you’ve ever had,” McVicar said. She also uses cinnamon basil on pizza “because the flavors go really well with the cheeses,” and she infuses white vinegar with purple basil. “It’s delicious, and it turns the vinegar pink,” she said. Basil can also be steeped into tea or soaked in warm milk for a drink to promote a good night’s sleep.
“Whatever you’re making, the top tip for cooking basil is to add it last,” McVicar said. “Put it on or in your dish in the last three minutes of cooking, so you get the strongest, most delicious basil flavor.”