Basil (Ocimum basilicum). Basil is a tender annual herb valued in many cuisines. There are several different cultivars of basil, the ones with purple leaves being especially ornamental.
Cultivation: Classic Genovese basil may grow 60 centimetres tall or more, while other cultivars are shorter. Sow seeds in pots with a moisture retentive compost or in the ground as soon as the soil warms up. Basil prefers full sun. Keep the soil evenly moist but not wet. Fertilize in-ground plantings a couple of times in the season with a 5-10-5 (N-P-K) product. Fertilize container-grown basil every three to four weeks if outdoors, or every four to six weeks if indoors. Pinch out the growing tips to encourage a bushy plant and remove flower buds to inhibit flowering. Basil is quick to bolt (flower prematurely) so make repeat sowings for a season-long supply. Harvest fresh leaves at any time but ensure enough leaves remain on the plant for it to continue growing. Basil is not frost hardy but can be sustained into the cooler months on a sunny windowsill. Basil can also be grown from cuttings.
Classic Genovese basil is highly susceptible to a downy mildew that will kill the plant. Water from below to avoid wetting the leaves. If you detect downy mildew, remove any uninfected leaves for use, then dispose of the affected plant in the household garbage. Some cultivars are more resistant and this characteristic may be noted in seed catalogues.
Disclaimer: Toronto Master Gardeners does not advise or recommend herbs for medicinal or health use. Any information in the recommended resources should be regarded as being for educational purposes only and should not be considered as a recommendation or an endorsement of any medical or health treatment.
For more information:
RHS ‘Herbs-Growing’ https://www.rhs.org.uk/advice/profile?PID=679
RHS ‘Grow your own Herbs’ https://www.rhs.org.uk/advice/grow-your-own/herbs/basil
University of Minnesota Extension https://extension.umn.edu/vegetables/growing-basil
Herb Society of America (HSA) https://www.herbsociety.org/hsa-learn/hsa-publications/hsa-quick-fact-sheets.html
Wisconsin Horticulture, Division of Extension https://hort.extension.wisc.edu/articles/basil-downy-mildew-2/
U of Massachusetts Center for Agriculture, Food and the Environment https://ag.umass.edu/vegetable/fact-sheets/basil-downy-mildew
Date revised: December 2021
Prepared by the Toronto Master Gardeners, these Gardening Guides provide introductory information on a variety of gardening topics. Toronto Master Gardeners are part of a large, international volunteer community committed to providing the public with horticultural information, education and inspiration. Our goal is to help Toronto residents use safe, effective, proven and sustainable horticultural practices to create gardens, landscapes and communities that are both vibrant and healthy.
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