African Blue Basil and Basil Downy Mildew

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African Blue Basil

Everyone knows and loves the wonderful basil plant and its many uses, notably pesto. Pungent pesto made from fresh basil is a wonderful accompaniment to pasta, bread, and just about any other food that you can find to slather it on. But African Blue Basil amps up the flavor switch a notch. It has a “licoricey” or almost a camphor or anise flavor that is hard to describe. The added benefit for me is that African Blue is not susceptible to Basil Downy Mildew which is running rampant throughout the United States.

Opal basil showing signs on the lower leaves of Basil downy mildew
Opal basil showing signs on the lower leaves of Basil downy mildew

African blue basil (Ocimum kilimandscharicum x basilicum ‘Dark Opal’) is an accidental hybrid between an East African basil that is native to Kenya, Tanzania, and Uganda that is valued for its exquisite scent, and a garden variety basil called ‘Dark Opal’, known for it eggplant purple coloration. It is a hybrid so it can only be grown from cuttings, not seed.

That is why African Blue has plum undertones and speckles, and has its unique aromatic taste. And contrary to what some people  believe, it is very edible, in fact quite delicious as pesto.

The makings of African Blue pesto
The makings of African Blue pesto

 Edible Landscaping

African Blue Basil is a very decorative plant and would fit right in with the craze of edible landscaping; you can eat it –  plus it is beautiful! Every part of the plant is edible-stems, flowers, and leaves. Covered with blooms all summer long, the slender flower spikes of violet buds open to lavender flowers.

Slender wands of flowers decorate the plant all summer long
Slender wands of flowers decorate the plant all summer long

A regimen of nipping the flowering stalks off a basil plant is normal for any other varieties but not African Blue. You want those flowers for garnishes so this is a strictly “leave it alone” plant. The 1- to 2 1/2-inch long leaves are a slightly grayed green hue with amethyst spattering on their undersides. The plant grows up to 2 feet tall  and is much bushier than regular basil varieties. One rooted cutting will supply you with plenty of pesto and edible flowers all season long. Throw the edible flowers into salads for a flavor sensation. Go to my post on Eat Your Flowers! for more ideas.

African Blue Basil
African Blue Basil

Cultivation

Plant African Blue Basil transplants in spring when all danger of frost is gone in a sunny spot and step back and let nature take its course. It will do well in a container and behaves well with other plants. Like all basils, it likes hot, hot sun and good drainage.

Pinching off the tips of basil stems makes the plant branch out laterally. Since this basil is a sterile hybrid, you can only purchase plants, not seeds. When you bring home your young plant,  pinch out its center stem to start this process. I naturally harvest it all season long for pesto and salads so the plant gets very bushy and lush. Don’t be afraid to pinch it to avoid floppiness later.

Making pesto-Gather ingredients and place in blender
Making pesto-Gather ingredients and place in blender

African Blue Pesto Recipe 

Place in your food processor: 1/4 cup olive oil, 1/3 cup water, 1/4 cup raw pine nuts, 3 cloves of garlic, chopped coarsely, and 2 cups of basil leaves, stems and flowers, chopped coarsely and packed lightly into the measure. Blend well, stirring large bits back into the mixture and reblending as needed. Transfer the mixture into a bowl and stir in 3/4 cup of freshly grated Parmesan cheese.  Add a sprinkling of grated black pepper. And sit back and enjoy this concoction on your pasta! You can keep this in the fridge with a layer of olive oil on top for a couple of weeks or freeze it. I freeze it in ice-cube containers for ease of removing throughout the winter.

Serve African Blue Pesto over pasta
Serve African Blue Pesto over pasta

Basil Downy Mildew

The latest malady to hit ornamental and food plants is Basil Downy Mildew, which has appeared in the last couple of years and is sweeping through the country like wildfire. It starts with leaf yellowing, which looks like a nutritional deficiency and then spots appear and can make the entire plant unusable. Under the right weather conditions (wet, warm weather), basil downy mildew can spread rapidly and result in complete loss of all your basil plants. Although Peronospora belbahrii, the pathogen that causes basil downy mildew, cannot survive our mid-Atlantic winters, it can be reintroduced on infected seed or transplants or by windblown spores.

Basil leaves infected with basil downy mildew
Basil leaves infected with basil downy mildew
Sweet Basil starting to be infected with Basil Downy Mildew at the base and then it moves up the plant
Sweet Basil starting to be infected with Basil Downy Mildew at the base and then it moves up the plant

It seems like every basil I plant gets the infection soon after planting, but the African Blue one remains immune for me. I love using Basil in cooking and this really upsets me as there is no known cure, other than applications of fungicides which are know to be damaging to bee populations. Even fungicides are not effective when the weather is wet and warm like it has been all spring and summer.

11 Replies to “African Blue Basil and Basil Downy Mildew”

  1. I’m not sure I’ll like this plant as I can’t eat licorice or anise. I love their scents though. I will give it a try though if I find it. Thanks for the recipe and the information

  2. Thanks for this article. This is a bad summer for basil in my garden. I love the opal basil for making a beautiful red vinegar, but it is not doing well. African blue…I’ll keep that in mind next year!

  3. Thanks for this information Claire. I have grown the African Blue in the past and not used it. How terrible. Every year I grow and use lots of basil. I am keeping your recipe and will give it a try. Really love the fresh basil pesto! Happy summer to you.

  4. I am so glad you took the time to write this post. I happen to have this one. I bought it this spring for the first time as I was drawn to the color for my outside garden. I find I enjoy growing herbs more than veggies. I love the blooms, and testing a nibble some time back, I felt it was very edible and, or yeah, tasty. But with winter approaching, I was researching how to cultivate basil, and what all is edible, and everywhere I was looking it was saying pinch off the flowers, they are bitter, blah, blah, blah. I was beginning to think my taste buds must be really off or something. And then I came across your post. Yes, yes, yes.

    It now makes sense why I so enjoyed the omelet I made this past weekend with fresh off the vine tomato (the only fruit/veggie I will now grow), feta cheese, and a small handful of the flower buds from a flower stalk of my basil. My African Blue Basil, that is. Yum.

    I now also know I need to take a cutting (or two or three) to prep for planting next spring.

    Thank you, again.

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