Water your basil plant once a week. Water at the base of the plant to avoid showering leaves and stems. Add enough water to moisten the soil, but do not saturate it.
Add a thin layer of mulch around your basil plant to hold the moisture in the soil and aid in preventing weeds.
Remove any flowers that appear on your basil plant by pinching or cutting them off. These can be detrimental to the plant's flavor.
Harvest your basil plant when temperatures are expected to reach 40 degrees Fahrenheit or lower, as these temperatures will ruin your plant. You may cut off leaves or branches to harvest, or cut the top of the plant off, making sure you leave about 6 to 8 inches of growth.