Question: What are the recommended techniques for growing basil in the Umpqua Valley?

Answer: Basil is called by many names like sweet basil or even Thai basil, but all of its common names refer to the herb’s botanical name, Ocimum basilicum. Basil is a member of the mint family (Lamiaceae), along with other culinary herbs like rosemary, sage and lavender.

It is believed that basil has its origins in India, but the herb has been cultivated for over 5,000 years with its reach spreading to all corners of the globe. In ancient Egypt, basil was used as an embalming and preserving herb and has been found in tombs and mummies.

For a long time, we knew just one kind of basil — ‘Genovese’ (Ocimum basilicum ‘Genovese’), named for where it was first grown near Genoa, on Italy’s Ligurian coast. This is the flavorful sweet basil familiar to Italian dishes where it is used liberally.

With its wide culinary reach, different varieties of the basil plant have been adopted into the cuisines of different cultures. Some other varieties include: Cinnamon or Mexican Spice (Ocimum basilicum ‘Cinnamon’), Lemon basil (Ocimum basilicum x citriodorum), and Thai basil (Ocimum. basilicum var. thyrsiflora). This variety of basil has a sweet taste with a hint of licorice. It is very common in Asian cuisine, especially Vietnamese dishes.

Basil is a warm-weather herb, needing six to eight hours of sun, and can benefit from some afternoon shade. Plant seeds or transplants after all dangers of frost have passed and the soil is warm. Plants are very frost-sensitive, so keep plants protected in case of a late cold spell.

Don’t rush basil. Without heat, the plant won’t grow well. To get a jump on the season, start the seeds indoors 6six weeks before the last spring frost.

Basil likes rich, moist, but well-drained soil with a pH of 6-7. Give your garden soil a great foundation by mixing in several inches of aged compost or other rich organic matter. Use an all-purpose fertilizer when planting. Thereafter, feed the plants every two weeks with diluted liquid fertilizer. During the dry periods in summer, water the plants freely.

If you live in a hot area, use mulch around the plants. Tthe mulch will help hold in moisture and suppress weeds. Don’t let your plants get too dry or growth may be stunted.

Plant your basil seeds/seedlings about ¼-inch deep and 10 to 12 inches apart. They should grow to about 12-24 inches in height. For larger varieties, plant about 16-24 inches apart.

Basil works in almost any type of pot or container, but there are two rules for success: keeping the soil moist and not crowding the plants. The easiest way to follow both rules is to plant in large, deep pots, which means more soil for moisture retention and more real estate for spreading out multiple plants and ensuring adequate air circulation. Overcrowded plants are vulnerable to fungal problems.

To encourage the plants to start branching, prune the branch tips back. Be sure to pinch off blooms to prevent your plant from going to seed. If your plants get away from you to the point at which they are making seeds and have stopped growing, shear off the top third of the stems and fertilize with a liquid fertilizer.

If you’re planning on drying your basil for later use or making pesto for freezing, grow at least a dozen plants. For other uses, one or two basil plants should be plenty. Many gardeners mix various types of basil in their flower beds, where it is ready for a quick harvest anytime.

Occasionally, basil is bothered by aphids or slugs. You can control these pesky insects using row covers or pyrethrins. Common diseases include powdery mildew and bacterial leaf spot. To prevent these problems, avoid overcrowding plants and wetting foliage.

The best method for storing basil is freezing. Freezing will prevent the herb from losing a good portion of its flavor. To quick-freeze basil, package whole or chopped leaves in airtight, resealable plastic bags, then place in the freezer.

Another storage method is drying the basil. Make easy work of this by cutting the entire plant off at ground level, and hang the plants in a warm, well-ventilated area for several days. You can rub the dry leaves into a container for storage.

You can also keep cut basil stems fresh for a few days by putting the ends in water just like a cut flower. They will add a fresh fragrance to the air.

Do you have a gardening or insect question? Contact the Douglas County Master Gardeners via email at Douglas County Master Gardeners are trained volunteers who help the OSU Extension Service serve the people of Douglas County.

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(1) comment


Chris, this was great. Thank you.

Most years, my basil does pretty well. My chief error is overcrowding, and neglecting to regularly and aggressively prune.

When pruning, it's a nice idea to strip the leaves for use, and then plant the stems (say, 4 nodes under, two nodes and maybe 1/2 a leaf above the rooting soil surface), which root aggressively and serve as a reward for your pruning efforts.

And who can ever have too much pesto?

Slugs are, of course, not insects. Made me wonder, though, about feeding basil to snails that are destined for buttery-garlicy Valhalla.

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