Growing Guide: Basil

basil growing guideDownload: Basil Growing Guide

One of the most widely grown culinary herbs, common basil (Ocimum basilicum) has a spicy-sweet flavor and an unmistakable aroma that signifies to many gardeners that summer has arrived!

Fun Facts

  • Basil is native to tropical regions in Asia and has been cultivated for thousands of years.
  • It’s related to mint and has the square stems typical of this plant family.
  • An essential flavoring in Mediterranean cooking, basil is one of the main ingredients in Italian pesto. It’s also used in Asian cuisines, including Thai and Vietnamese dishes.
  • Don’t refrigerate fresh basil. Instead, keep cut stems of basil at room temperature in a jar of water.
  • Dried basil is a popular addition to soups, tomato sauces, and pizza toppings and is a must-have in Italian herb blends. However, dried basil lacks the bright flavor and distinctive aroma of fresh basil.

Choosing Varieties

Plant breeders have developed dozens of varieties of basil with a wide range of leaf colors and sizes, scents, and flavors. Here are some of the most popular:

  • Genovese basil has large, deep green leaves and is popular for making pesto.
  • Opal basil’s deep purple leaves are a stunning addition to salads, garnishes and flavored vinegars.
  • Cinnamon basil has the distinctive spicy flavor and aroma of cinnamon.
  • Lemon basil and lime basil have citrusy scents and flavors.
  • Thai basil has an anise-clove aroma and spicy flavor and is popular in soups and curries.
  • Opal basil and Thai basil have especially attractive flowers that make them beautiful additions to floral arrangements.

Site Selection and Preparation

Basil needs full sun — at least six hours of direct sun each day — and rich, moist, well-drained soil. Raised beds are ideal for growing basil, because the soil warms up faster in spring than the soil in in-ground beds. Loosen soil to a depth of at least 8” and mix in some compost and slow-release fertilizer. Basil is also ideal for growing in containers.

Starting Seeds Indoors

True to its tropical origins, basil is a heat lover and will suffer if temperatures drop into the 50s F. Get a jump on the growing season by starting basil seeds indoors about six weeks before your average last spring frost date. Fill small (3-4” diameter) pots with moist seed-starting mix, and then scatter the small seeds thinly over the surface. Cover with 1/8” to ¼” of planting mix and then spritz with a plant mister to settle the mix and ensure good contact with the seeds. Keep the pots at warm room temperature (around 70 degrees F.); seeds should germinate in about a week.

Place the seedlings in a sunny window or, better yet, under grow lights. When seedlings are a few inches tall, thin them by snipping off extra seedlings, leaving just one or two of the strongest plants per small pot. (Enjoy the “thinned” seedlings in a salad.)

Plan to transplant the seedlings outdoors a week or two after the last frost date, or when nighttime temperatures stay in the 60s. Be sure to acclimate indoor-grown seedlings by hardening them off over the course of seven to 10 days, starting them off in a sheltered spot outdoors and gradually exposing them to increasing amounts of sun and wind.

In regions with long, warm summers, you can direct-sow basil seeds right in the garden.

Ongoing Care

When plants are about 8” tall, pinch or snip the main stem back to just above a set of leaves; new shoots will form where the leaves meet the stem. Continue to pinch stems over the course of the growing season to encourage the plants to form shrubby mounds of young, tender leaves.

Check soil moisture frequently and water as needed to keep soil evenly moist. Keep in mind that the soil in containers will dry out more quickly than the soil in garden beds.

Toward mid-summer, the plants will begin producing flowers. If you’re growing basil to eat, pinch off the flowers as they form to encourage leafy growth. You can also let some flowers develop to use in arrangements.

Growing Basil Indoors

You can start basil seeds any time and grow them indoors under lights, transplanting them to larger pots as needed.

Basil can also be easily grown by taking stem cuttings from existing plants.  Taking a cutting involves removing a piece of a stem with 3 or 4 leaves and placing it in a growing medium where it will develop new roots. Basil cuttings are easy to root in moist potting soil, but will also be successful if placed in a jar or vase of water. If placed directly in water, once roots form, you can repot your new plant into soil or move it to a hydroponic system where necessary nutrients are provided through their water source.