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Dark Opal Basil : Grow & Care for Ocimum basilicum 'Dark Opal'

Written by Iris

Aug 02 2021

Dark Opal Basil : Grow & Care for Ocimum basilicum 'Dark Opal'
This sweet and very popular variety of basil has gorgeous purple-black glossy leaves and a delicious aroma. It is striking and a beautiful and colorful garden plant. This basil produces young leaves of small to medium size. It is a slow bolt and grows at a steady rate. Deep purple has a green metallic undertone or luster, and in bright light it can appear flat and open.

How to Choose and Prepare a Planting Site

Plant seeds/seedlings about ¼-inch deep and 10 to 12 inches apart. They should grow to about 12 to 24 inches in height. Basil will grow best in a location that gets 6 to 8 hours of full sun daily, though it can perform well in partial sun, too. Soil should be moist but well-drained. Basil works great in containers or raised beds, as these allow for better drainage. If you’re planning on cooking with these plants, plant in clean soil, don’t use insecticides, and grow them away from driveways and busy streets so that exhaust won’t settle on the plants.
Dark Opal Basil

How to Grow Dark Opal Basil (Ocimum basilicum 'Dark Opal')

Steps for Dark Opal Basil (Ocimum basilicum 'Dark Opal') Propagation with Seeds

  • Plant seeds in a small pot, making a 1/4-inch indentation in the soil with your thumb. Use moist, sterile planting soil. Place the seed in the indentation and cover it with loose soil. “Water in” the basil by thoroughly saturating the soil. Place the pot near a sunny window. Keep the soil consistently moist during germination, which takes about 14 to 21 days.
  • Select a planting site that receives full sunlight exposure. Dark opal basil prefers light, rich, well-drained soil with a pH range of 5.5 to 6.5. Amend the soil with 1 to 2 inches of manure and 4 to 6 inches of compost, working them into the top 6 to 8 inches of soil.
  • Transfer the dark opal basil plant to this soil 6 weeks after planting it in the pot, during the spring when soil is warm. Make a hole big enough for the entire root system and water-in the plant by saturating the loose soil. Keep 18 inches of space between plants.
  • Apply a 1-inch layer of organic mulch around the base of the plant to help it retain moisture.
  • Provide the plant with 1.5 inches of water per week. Water the roots slowly and deeply.
  • Pinch off growing flower buds by hand as they appear, to encourage bushier growth.

 

Steps for Dark Opal Basil (Ocimum basilicum 'Dark Opal') Propagation with Scion

As an alternative to sowing, the basil can also be propagated by using cuttings. Since this method is usually not successful using a potted mother plant from the supermarket, it is recommended to take the scions from a strong bed or balcony plant.
This is how to turn a scion into a new basil herb:
cut off five to ten shoots with a length of about ten centimeters and remove the leaves from the lower halves
place the shoots in a translucent vessel filled with water
position the cuttings in a light place but not exposed to the bright midday sun
renew the water every two to three days
as roots have developed after about a week, the cuttings can be planted in substrate together
keep the substrate constantly moist, but not too wet
optimal temperature: between 20 degrees Celsius and 24 degrees Celsius
best time for propagation: April
Dark Opal Basil

How to Care for Dark Opal Basil (Ocimum basilicum 'Dark Opal')

Light

Unless you live in particularly hot regions, your dark opal basil will appreciate a full sun position. Ideally, they'll want at least six hours of full sun to thrive.

Soil

Not very picky about soil types, this basil variety just needs a well-drained variety that is not overly dry. Mulching can help dry soil retain water better, especially in hot areas, and adding organic material can be welcome if your basil is grown in a less rich medium.

Water

Make sure that the soil is moist. Basil plants like moisture. If you live in a hot area, use mulch around the plants (the mulch will help hold in moisture and suppress weeds). During the dry periods in summer, water the plants freely.

Temperature and Humidity

The key to success is to place the dark opal basil in a hidden place. Without this, it is unlikely to flourish. Although the species can cope with hot, humid or dry conditions, it prefers cooler, milder areas. Too much heat means the leaves are more green than purple, and it affects their flavor intensity. The species is also very sensitive to frost and is best kept indoors if temperatures drop sharply overnight.

Fertilizer

Fertilizing your black opal basil regularly helps ensure healthy growth. However, you do need a balance. Overfertilizing can affect the intensity of the smell and make it less aromatic. This is because the plants will produce less oil. Make sure the fertilizer is not too strong and you don't use too much.

Pruning

When seedlings have 3 sets of true leaves (not counting the initial seed leaves), pinch off the top set. Continue this pattern when harvesting, pruning each branch you harvest back to just above its first or second set of leaves.  Keep pinching off flowers as your basil grows to extend its harvest time. Flowering will change the flavor of leaves and reduce leaf production. Like many herbs, basil does well with relatively heavy and frequent harvests or pruning.

Pests and Diseases

Slugs can be a problem, especially during the late spring and early summer. It is advisable to use natural slug control remedies such as beer traps and crushed egg shells as opposed to slug pellets. Aphids can also be a problem so best be vigilant and remove them with a jet of water or introduce a biological control method, such as ladybird larvae.
Dark Opal Basil

Dark Opal Basil (Ocimum basilicum 'Dark Opal') FAQ

Is Dark Opal Basil the same as basil?

Opal basil has striking, dark-purple leaves, and a milder flavor than sweet basil, with hints of cinnamon, anise, mint, and clove. It's a beautiful accent to salads or other uncooked summer dishes, either in addition to or in place of sweet basil.

Is Dark Opal Basil edible?

Dark Opal Basil (Ocimum basilicum 'Dark Opal') is a pretty-looking, aromatic basil cultivar. This upright, bushy perennial is more frequently grown as an annual and has edible deep purple leaves.

Does Dark Opal Basil grow back?

There are a few varieties of Dark Opal Basil , but all are cultivars of the same basil plant, which is a true annual. Therefore purple basil grows from seed and die again all in one season, and do not return year after year.

How long can Dark Opal Basil live?

Dark Opal Basil may survive for two years before replanting in warm climates. An indoor basil plant with full sun and steady warm temperatures may last longer as well. Basil plants are sensitive to cold weather and frost. Before the weather turns, take steps to preserve your plant for the next year