There are a number of related basil plants that answer to the name lemon basil. they all have similar attributes and some are indistinguishable from others. Thai lemon basil is one of the more common, others include Mrs. Burns, which has a much stronger citrus flavor and aroma than its cousins. Maenglak Thai lemon basil has a stronger clove and cinnamon flavor / aroma. Others include Penang lemon basil and lime basil. Common Lemon Basil [O. americanum] is known as American Basil and sometimes hoary basil.
Lemon basil has light green, narrow oval leaves with jagged edges. The leaves average 2 to 2.5 inches long. Its delicate white blooms are also citrusy and aromatic. It should only be permitted to flower if seed saving, once the plant bolts the flavor wanes.
1. Basil can be grown as a perennial only in USDA hardiness zones 10 and higher, Elsewhere, it is a tender annual that will die off with the first cool weather if not transported indoors.
2. Some variation among specific cultivars
Basic Care of Basil
Water - Basil requires ample and persistent water. Mulch to retain moisture in warm weather is advisable.
Delicate flowers on Basil are attractive however they are a sign your plant is going to seed and production will decline at this point. If you are not looking to harvest seeds, you should pinch off any flower stems as they appear.
Temperature - Basil thrives in warm temperatures and heat. It will turn black and die off in temperatures approaching the mid 30s F. Temperatures should be at the very least in the 70s around the clock.
Optimal Growth Temperature 65 to 85 F
Germination Temperature 70 to 75 F
Pests and Disease
Basil has some enemies, Beetles, particularly Japanese Beetles, love Basil as much as people do and have been known to completely skeletonize whole plants. Aphids are also a problem at times. Most varieties are also subject to various plant diseases such as black spot, gray mold and fusarium wilt.