African Blue Basil (Ocimum kilimandscharicum × basilicum ‘Dark Opal’)

20181215_085059awerfI have a lot of plants in my garden that are “bee magnets”, but few will be carpeted in the buzzy little critters like my African Blue Basil.  And then there’s pesto!

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*A handy growing summary chart is at the end of the article.*

African Blue Basil is a hybrid between a large basil native to Africa that is high in camphor, and Dark Opal Basil, a cultivar of sweet basil with purple leaves.  The result is a larger plant with a slightly stronger flavor than typical basil and that produces a profuse array of light purple flowers (see the video at the end!), but due to it being a sterile hybrid it won’t go to seed.  That means this basil is one of the few that are perennial.

20181215_085127xdfgGrowing African Blue Basil is fairly easy.  Like other basils, African Blue Basil prefers full sun, but will tolerate morning or afternoon shade in hot weather.  This basil is also a little more heat tolerant than other types of basil.  Since most varieties of basil are annuals, summer temperatures trigger flowering which then means the plant will soon die off as it goes to seed.  Keeping an annual basil alive longer means repeatedly pinching back the flowers to prevent seed formation.  However, since African Blue Basil is sterile, you’ll get to enjoy a near endless flower show without having to worry about constantly removing the flowers to keep the plant alive.

African Blue Basil is a fast grower, and since it is perennial, will continue to grow until it reaches roughly 3 foot tall and wide.  Over time it will form thick, woody branches.  Sometimes those branches can become heavy over time with increased growth and may flop over.  The plant can be easily trimmed to shape it as desired since new shoots will form readily out of older stems.

20200724155535_IMG_4963African Blue Basil can handle slightly drier soils than other types of basil since it will have roots that grow deeper down.  However, it isn’t really a drought tolerant plant.  When plants are younger, they will need consistently moist soil but you can reduce watering once it is established.  Putting a layer of mulch over your soil will conserve moisture and help the plant, especially in hotter weather.  Avoid over watering as the plants’ roots don’t like being waterlogged.

20180923_135351Like pretty much all basils, African Blue Basil is not frost tolerant.  I’ve seen some sources claiming that they can take the cold, but I’m not sure what they consider “cold”.  African Blue Basil will continue to flower right up to winter, but the moment the temperatures hit the freezing point an unprotected plant is going to die back significantly, if not completely.  That means USDA zones 10 and up are fine, but the rest of us need to plan ahead (I’m in USDA zone 9A).

For light frosts, wrapping the plant in incandescent Christmas lights works beautifully (see my post for the how-to here).  The exposed parts of the plant will die, but don’t trim them off.  They will act like a heat shield keeping the warmth from the lights around the crucial part of the plant, which is the base stems.  If those don’t get damaged, a whole new plant will grow from them as soon as the temperatures warm up even a little.  If you live in zone 8 and below, your options are to grow this in a large pot and bring it indoors to hang out during the winter, or to take cuttings to propagate a new plant that will be ready for spring planting once danger of frost is past.  Remember, it’s sterile so there are no seeds to buy!  Take cuttings of strong green stems and either start them in a cup of water, or better yet, stick them into potting soil that is kept very moist until new roots form.  Take a handful of cuttings just in case some don’t root.

I have found this plant to be exceptionally tolerant of a whole host of circumstances.  I have kept one going for several years now, even after repeated die backs from at or near freezing temperatures (those lights REALLY do work).  I have also needed to move the plant to three different locations for various reasons and it has handled the transplanting process perfectly.  The plant was at mature size each time and so we trimmed it down considerably and dug out as much of the main root section as possible.  By keeping it well watered until signs of new growth emerged, it was able to take each move like nothing happened.  In less than a couple of months it was back to full size (yes, it’s a fast grower!).

20200724155351_IMG_4959This variety of basil isn’t commonly available in the local nurseries around here, but you can find it pretty easily online.  This could be due to it being frost sensitive, not well known, and not as used for culinary purposes as other basils.  Though the flavor of African Blue Basil is stronger than that of the more commonly used sweet basil varieties, it makes an awesome pesto (check out some recipes that use pesto here) and tastes great with tomatoes and feta that have been drizzled with olive oil.  Pick the leaves in the early morning while the temperatures are still cool when the leaves will have more moisture and the flavor compounds will be in higher concentration.

Plant Summary:

  • Perennial: Plants are often grown as annuals in colder climates
  • Evergreen: If temperatures go to freezing and below, the leaves and green stems will die back
  • Height: 3 feet at maturity
  • Width: 3 to 4 feet
  • Sun: full sun, can take some morning or afternoon shade in hot areas
  • Water: regularly, not drought tolerant
  • Soil pH: neutral to slightly acidic
  • Soil type: amend heavy clay or loose sandy soil
  • Key nutrients: fertilize if needed with a balanced fertilizer
  • Planting time: best to start in spring after any danger of frost has passed
  • Zones: 10 and up, but can tolerate zones 8 and 9 with frost protection, below that grow as an annual or bring indoors during winter





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