How to Grow Basil

By Regina Farley

Whether you’re out to conjure up a mouthwatering pesto, add a touch of splendor to your landscape or find a best friend for your tomato plant, basil is up to the challenge. Although among the world’s oldest and most commonly used herbs, basil has a hardy disposition and surprising number of uses that make it a compelling addition to any garden or decorative landscape.

While best known for its use in Italian cooking, it is also used in many ethnic culinary creations. From Greek pesto to Thai stir-fry, savory tomato sauce and even cheesecakes, basil is really quite the cosmopolitan spice! It also gets along well with many vegetables growing in your garden. Basil is an ideal companion plant for tomatoes. Few people realize that basil enhances the flavor of the tomato plant simply by growing next to it. Additionally, basil helps protect tomatoes and other plants against certain insects.

Soil and water requirements for basil plants

Basil seems to prefer a lighter (or sandy) soil, but will grow in raised beds or clay soil that is well-composted and well-drained. Well drained soil is absolutly essential for a happy, healthy basil. During the growing season, most basil plants prefer warm temperatures (above 55 at night) and moist, well-drained soil as they tend to perform poorly in cold, wet conditions. Basil is somewhat forgiving about soil pH (acidity and alkalinity) and will tolerate a range of about 5.5 to 8. A local nursery professional or university extension agent can help you determine if the soil conditions are right for your plant.

In milder summer climates, a generous watering can easily last most basils planted in beds for several days. However, basils grown in arid regions or climates with hot summers will happily soak up daily sprinklings with your garden hose. When planting in hot and dry areas, it’s a good idea to protect your basil plants from as much stress as possible: A heavy mulch will greatly help prevent water stress and discourage some diseases.

A self-watering planter is a great investment for people with limited space and time (and it is particularly ideal for procrastinators like me). Water-absorbing polymers mixed into the soil can help keep the soil moist during times when you forget to water in the summer. A thick application of compost (up to six inches) tilled into the soil will help absorb water and moderate soil temperature. You can make your own compost from yard and garden refuse using compost bins and worm bins.

Basil fertilizer requirements

Keeping your plants well-fertilized is important, but to avoid fungal and bacterial wilts, you should not feed at temperatures below 60 degrees. Basil tends to like a variety of fertilizers, but it performs best with organic or slow-release fertilizers. Worm-casting tea, compost tea and Garrett Juice all make great basil fertilizers. A strong application of any fertilizer will make the plant more susceptible to insects and diseases.

Additionally, fast-release or artificial fertilizers should be avoided as they will give the plant an undesirable flush of growth that may not be as tasty. Think of artificial fertilizer as plant junk food!

If starting from a transplant, make sure you give your plant a dose of liquid seaweed and a root-stimulating fertilizer such as HastaGro Plant Food or Garrett Juice. Under the right growing conditions you can expect a four-inch transplant to attain an easily harvestable size in approximately one month. It can be pinched back for culinary use sooner, but take care not to get eager and snip too much!

How to Plant Basil

Most basil is easily propagated by cuttings. In fact, cuttings are an excellent way to sustain a favorite basil plant from one growing season to the next. Just make sure the soil mix is well-drained and not too rich as a richly composted medium may encourage rot.

Most of the culinary basils should be planted about 12-15 inches apart. The distance between ornamental basils will depend on the variety and type, but most ornamentals need significantly more room to reach their full potential. Because basil does not withstand foot traffic well, you should select a planting spot far from the path of garden guests or pets.

To give your outdoor basil a jump-start, solarize the soil. This may sound technical, but it really isn’t. Just spread some clear plastic over the planting area, weight down its edges and let the soil bake for two to three weeks. To give your basil seeds an earlier start indoors, use a bottom heat source in your seed tray to trick your plants into coming up early.

If starting from seeds, you should water the seed tray with a liquid seaweed solution. Liquid seaweed has a lot of natural growth stimulants and micronutrients that your seedlings will appreciate. Also, you should use a soil additive that contains a high phosphate content such as soft rock phosphate. The available phosphate within these additives is very important to the development of seedlings.

At 7 to 14 days, your seedlings should start to appear. However, keep in mind that seeds will germinate only in warm soil above 55 degrees. If planning seeds outdoors, wait until late spring when temperatures are above 60 degrees. You should be able to harvest green leaves from seed in approximately six weeks. You should not harvest your plant until it is at least four inches tall with a minimum of six mature leaves, but don’t take more than half of them.

Basil Diseases, and How to Avoid Them

Again, well-drained soil is essential to the success of your basil and probably the best preventive action you can take against common soil-borne fungal diseases such as pythium wilt (damping off) and fusarium wilt. Fungal and bacteria wilts are best avoided by planting and growing properly.

Because little can be done to reverse the effects of such diseases, prevention is really the key. As seedlings are especially susceptible to fungal diseases, starting with transplants from your local nursery can also help you avoid fungal wilts. Ensuring adequate air circulation can also help stave off unwanted diseases. Dusting soft rock/colloidal phosphate on the surface of the soil and incorporating it into the potting mixture of seed trays and pots can also prevent the spread of pythium wilt.

If a batch of these rotten fungi or bacteria pops up, there are a few things you can do. Horticultural cornmeal works on a variety of soil-borne fungal diseases. Garlic fungicide spray can work on many disease and insect problems. Sprays made of whole milk (no, I am not kidding!) will sometimes kill the offending disease. Also, cedar flake and hardwood mulch have been somewhat successful at preventing wilt and foliar disease. However, an over abundance of mulch in seed trays (more than one-tenth of one inch) can prevent your basil plants from coming up. Sometimes these remedies don’t work, and starting over is the best option. Avoid overwatering basil plants.

Basil Pests, And How to Avoid Them

Most of the insects that attack basil are caused by water stress, cold or cool weather, not enough sunlight or poor drainage. Here are a few solutions to the most common insect hordes:Liquid seaweed can help eliminate a lot of insects that plague basil, including aphids, mealybugs and spider mites.Bacillus Thuringiensis (Bt) spray can permanently shut down the mini logging operations of leaf- and stem-eating worms.Citrus oil/d-limonine sprays and canola/pyrethrum mixtures can send the more persistent, lousy grasshoppers and leaf beetles straight to that garden in the sky. However, the grasshoppers are usually the most difficult to eliminate as they are resistant to almost any spray and they multiply so quickly you might think they’re resurrecting themselves!

Types of Basil

Thai basil – Characterized by its strong licorice fragrance and flavor, this annual is also referred to as anise or licorice basil. It reaches heights up to 24 inches and with a nearly two-foot expanse. Great for stir-fried dishes, Thai basil is more easily found in specialty grocery stores that carry exotic or high-end fresh herbs.

Genovese basil – A well-regarded favorite among foodies, Genovese basil is considered the best basil for use in Italian recipes (pesto, tomato-basil sauce, Caprese salad, etc.) Like sweet basil, this annual has a strong clove fragrance and ranges from 12 to 24 inches in height, but is easily distinguished by its more crinkly and in-turned leaves.

Lemon basil – Similar to the other basils, this annual grows to a height of about two feet, but complements salads, dressing and teas with a savory lemon flavor and fragrance. This basil is a bit spindlier than its other basil relatives and is characterized by a flatter, narrower leaf.

Cinnamon basil – The name describes it all – basil with a cinnamon flavor. As you can imagine, its strong cinnamon scent easily distinguishes it from the others. It also has a somewhat harrier leaf. This medium-sized annual grows up to 2 ½ feet tall and produces pale pink to purple flowers. Enjoy!

Perilla, Shisho (a basil relative) – There are a few kinds of perilla but this species, with green leaves and purple spots is perhaps the best for cooking. Used most often in Asian cuisine, Shisho has a cinnamon-lemon flavor. Perilla frutecens var “autopurpurea” (also known as a beefsteak plant) is an interesting relative that I’ve included here because of its much stronger licorice flavor that some cooks thoroughly enjoy.

Because it is often confused with coleus, it can double as ornamental basil. Please give all types of perilla plenty of room to roam. Even though it’s an annual, it spreads (without mercy!) from seed. This very aggressive species is a great plant for people with brown thumbs.

Ornamental basil plants

Basil: It’s not just for dinner any more! Many gardeners don’t realize that one of the best uses for basil is that of an ornamental in their landscape. Ornamental basil is colorful, attracts beneficial insects and is heat tolerant. Additionally, most can be used in the same fashion as many sun-loving coleus as they all belong to the mint family. While the basils discussed below are recommended primarily for their decorative properties, most can also double as a culinary spice.

Siam queen basil – A personal favorite, Siam queen is a type of Thai basil that produces mint green leaves with very large flower heads – up to 6 inches across – that give off a spicy anise scent. (It might seem strange, but it smells great!) It reaches heights up to 2 ½ feet, but it can be pinched back – and even eaten! – to restrict growth.

Dark opal basil – Dark opal resembles a glossy-leafed, burgundy-and-purple coleus with pink flowers. While this two-foot annual is great for landscapes, it can also add a hint of exotic color to culinary favorites such as Italian Caprese or spring garden salads.

Purple ruffles basil – This is a great plant to spice up the kitchen and the landscape! Perhaps the most colorful basil for landscapes, purple ruffles makes a great addition to salads and pesto. Similar in color to the dark opal, this plant is slightly smaller in stature (reaches up to 1 ½ feet) and its leaves are very frilly and ruffled. While it can handle a shadier spot in the garden, it still needs at least three hours of sunlight to mature properly. Purple ruffles gives off a combination of licorice and cinnamon scents and produces lavender and pink flowers that can also be eaten. Somewhat difficult to start from seeds, this plants works best from transplants.

African blue basil – While not recommended for culinary uses, African blue basil is more often used as an ornamental. Besides, you’ll be so proud of this one, it would pain you to eat it! A properly tended plant with plenty of room to expand can easily become a grand showpiece in your late spring or early summer garden, making itself the center of conversation among your guests. In zones 9 (maybe 8A) and warmer, given the right protection, this beauty can sometimes transform itself into a cherished perennial.

Because it can mature to four feet, African blue basil works best at the back of an annual border. Its wonderful pink and purple flowers with purple stems and leaves add to its desirability. In fact, many gardeners choose this basil in place of pink- or purple-flowering sage. There’s no need to be afraid of this plants ample volume as, like most basils, it is easily trimmed back.

Holy basil – The attractive green and purple foliage of this perennial, combined with a strong showing of pink and white flowers, make this is an ideal landscape addition. Reaching heights up to three feet with a two-foot span, this hairy-leafed plant produces a fragrant clove scent. While holy basil can be used for culinary purposes in cooked foods, its hairy leaves and woodier stems make it difficult for use as a fresh herb. Holy basil stands the best chance for returning year after year in zones 9 or warmer.

Perilla (a basil relative ) – Perilla frutecens var “crispa” and “autopurpurea” are also interesting relatives of basil that can be used as ornamentals. Autopurpurea is almost entirely purple while crispa has very frilly, divided leaves. Both of these plants can take a little more shade than regular basil, but you shouldn’t expect it to develop the best flavor without more sunlight. Like its relatives, it needs plenty of growing space as it also spreads wildly from seed. Another great plant for the brown-thumbed gardener.

Harvesting Basil

It’s best to harvest your basil before it flowers as it tends to have a better flavor then. While you can harvest basil from the side stems of the plant, harvesting the leaves from the top will encourage a bushier, fuller plant.

According to some experts, including Howard Garrett, basil is best harvested late in the day when sugars have built up causing flavors to be more intense. Additionally, basil harvested at the end of the day will have a longer shelf life.

If your basil crop is larger than an Italian restaurant can use in an entire season, or if a freeze is headed your way, there are a few ways you can savor your basil later:

Freeze the leaves – Blanche basil leaves and quickly place them in an air-tight plastic bag in the freezer. The downside to this storage method is that the basil tends to turn a dark color, making it unsightly. Unless your dinner guests have a palette for blackened basil goop, it’s best to use this method for recipes that call for basil to be well-blended into cooked foods. That way your guests can enjoy the taste of your basil without being subjected to its less-than-attractive appearance.

Salt the leaves – Using sea or kosher salt, pack alternate layers of salt and basil leaves in a container (glass or plastic). Take care to fully cover basil layers with salt and make sure there are not too many overlapping leaves of basil. If the basil leaf layers are too thick, you may just be growing a very large container of mold spores. Place a layer of salt on the top, seal and place in the freezer. The contents should last for several months. Reuse the salt in other cooking projects or to make a new batch of preserved basil leaves. This method is believed to be the best for keeping the original basil leaf intact.

Grind and freeze – Puree basil leaves in a food processor, mixed with a small amount of water, pour into ice cube trays and freeze. This method allows you to use your basil in small increments.

“Preserve” in oil – This really should not be used as a long-term preservation method, unless you have a natural immunity to botulism poisoning! (Even if you do, your dinner guests probably won’t!) Use this oil quickly (within two weeks) and keep it in the fridge!

Preserve in vinegar – Basil vinegar is a better, and definitely safer, preservation method than basil oil. To use this method, chop basil, place inside a glass jar, pour warm vinegar into the jar and cap with a corrosion- and acid-proof lid. Store it in a cabinet or refrigerator for a while and shake (not stir) regularly to develop flavor. Do not use second-rate white vinegar on good, fresh basil. That’s just wrong!

In case you didn’t know, do not eat any of these if mold is present or if they have a rancid smell.