Growth and Care of Basil


Photo courtesy of MewnBeam at

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.

    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.

    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!