The best way to Plant and Develop ‘Darkish Opal’ Basil

Ocimum basilicum var. basilicum ‘Darkish Opal’

There are few herbs and greens which might be so attractive they may work solely as decorative plantings. ‘Darkish Opal’ is one such plant.

The deep purple, barely ruffled leaves make a sublime anchor to inexperienced foliage or a stunning distinction to colourful flowers like marigolds.

A horizontal close up of the dark purple leaves of a 'Dark Opal' basil plant.

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In fact, it’s not all in regards to the appears. Sure, it’s an attractive herb, however this candy basil cultivar additionally tastes marvelous.

You’re not giving up any of the basil taste you understand and love whenever you develop this magnificence.

Most of us develop basil as an annual, for the reason that leaves are likely to develop into more durable because the plant ages and since it’s solely hardy in USDA Rising Zones 10 to 12.

You’ll be able to be taught extra about easy methods to develop basil in our information. On this information, we’ll set you on the trail to ‘Darkish Opal’ success.

Right here’s what we’ll focus on:

I’m certain you possibly can’t wait to begin having fun with your crops, so let’s dig in.

Cultivation and Historical past

‘Darkish Opal’ was bred by Dr. Joseph M. Lent and Dr. John Scarchuk, professors on the College of Connecticut’s Horticulture and Plant Breeding program.

The pair recognized basil varieties from Turkey that had purple and inexperienced variegated leaves and determined they needed to refine the crops to create a cultivar that was totally purple, from stem to flower spike.

A horizontal photo of several 'Dark Opal' purple basil plants on a wooden table.

After a couple of years of selective breeding, they managed to create a uniformly purple plant with a delightful taste. It hit the market and was an immediate smash hit with growers.

‘Darkish Opal’ acquired the All-America Alternatives Bronze Medal and the All-America Alternatives winner within the Vegetable class in 1962, the 12 months Ferry-Morse Seed Firm launched the seed to the market.

It wasn’t lengthy earlier than residence growers fell in love with this cultivar, and the plant quickly gained recognition in residence gardens.

The colourful hue is brought on by the excessive stage of anthocyanins, which is identical pigment that turns potatoes, eggplants, and tomatoes purple.

Crops develop this pigment as a approach to assist them resist environmental stressors like drought, pathogens, and hungry herbivores. We principally like them as a result of they give the impression of being fairly, however purple crops may also have quite a few well being advantages.

The anthocyanins chargeable for the purple coloration may also alter the style. Within the case of ‘Darkish Opal,’ the leaves lack the brilliant, spicy notes of your common candy basil (O. basilicum), although they’ve a broadly comparable taste.

It has a extra delicate taste that’s earthier than candy basil, a touch of lemon-lime, and a very good crisp texture, making it good whenever you need a bit extra subtlety than the licorice-heavy Thai basil (O. basilicum var. thyrsiflora).

It’s no slouch within the olfactory division, having a stronger scent than candy basil. ‘Darkish Opal’ is slower rising than many different basil cultivars and it takes about 90 days for the plant to mature.

‘Darkish Opal’ Basil Propagation

There are a number of methods to propagate ‘Darkish Opal.’

You’ll be able to divide the crops you purchase on the grocery retailer, take cuttings, or sow seeds – whether or not you harvest them from an present plant or buy packets from a nursery.

Rising from seed takes the longest, however they’re low cost and available, and you’ll produce a number of crops from one seed packet. In case you go this route, contemplate succession planting so that you’ve got a prepared provide of ‘Darkish Opal’ all summer time lengthy.

Cuttings require an present plant and take a bit extra nurturing, however they mature faster than seeds.

Dividing grocery crops is the costliest approach to get began, however you’ll have the ability to harvest the leaves rather more rapidly than the opposite two strategies.

Whichever technique you land on, go to our information to basil propagation for a complete overview of the method.

The best way to Develop ‘Darkish Opal’ Basil

As with different varieties of basil, ‘Darkish Opal’ wants full solar to develop and look its greatest, however intense warmth within the afternoon can bleach or burn the leaves.

A bit afternoon shade is useful, significantly in highly regarded climates. Simply attempt to give it as a lot solar as doable since full solar helps the plant develop the very best shade.

A horizontal close up of the dark purple foliage of a 'Dark Opal' basil plant.

Whether or not you select to develop your crops in containers or within the floor, the soil should be well-draining. Amend backyard soil with well-rotted compost or manure.

Select a potting combine for container-grown crops that accommodates elements like humus, moss, perlite, rice hulls, or vermiculite to enhance drainage and support water retention.

My private choice is FoxFarm’s Ocean Forest Potting Soil Combine, which has bat guano, peat moss, earthworm castings, and fish meal. It makes all my houseplants and potted herbs completely happy.

FoxFarm Ocean Forest Potting Soil Combine

Decide up 12 quarts at Amazon.

Whereas ‘Darkish Opal’ will tolerate a reasonably huge soil pH vary, barely acidic to impartial is greatest, with one thing between 6.0 and seven.5 being superb.

Whenever you’re transplanting seedlings or nursery begins, house them about six inches aside to permit for enough air circulation which may also help inhibit fungal illnesses.

The soil or potting medium ought to be saved constantly moist however not moist or soggy. Think about the feel of a sponge that you simply’ve wrung out rather well. That’s what you’re aiming for.

In case you’re rising your ‘Darkish Opal’ basil indoors, ensure that the crops obtain at the very least six hours of direct daylight and that the container you select has drainage holes to permit the water to expire.

Needless to say in the event you maintain your own home cool, development might be gradual. These crops want temperatures of between 70 and 90°F to essentially thrive.

For that motive, in the event you’ve began your seeds indoors, make sure you wait till temperatures are constantly above 50°F earlier than planting out.

The crops ought to be fed commonly. A gentle, balanced fertilizer utilized as soon as a month is excellent, whether or not you might be rising within the floor or in containers.

I’m a fan of All the way down to Earth’s merchandise as a result of they’re made with pure elements and are available in compostable containers.

Their Vegetable Backyard combine has an NPK ratio of 4-4-4 and is constructed from fish meal, alfalfa meal, and kelp, amongst different elements. Your ‘Darkish Opal’ basil will find it irresistible.

A vertical product photo of Down To Earth Vegetable Garden fertilizer in a cardboard box.

All the way down to Earth Vegetable Backyard Combine

Decide up one-, five-, or 15-pound containers at Arbico Organics.

Rising Suggestions

  • Plant in full solar, with afternoon shade in highly regarded areas.
  • Present well-draining soil or rising medium.
  • Preserve the soil constantly moist however not moist.


The one upkeep required when rising ‘Darkish Opal’ is to pinch out the flowering ideas. Observe the flower spike right down to the primary department or set of huge leaves.

Minimize the spike off simply above the department or leaves.

A horizontal close up photo of the top of a 'Dark Opal' basil plant where it is starting to flower.

I’ve made the error of pinching off a flower spike greater up, and it at all times comes again and brings alongside some pals. You actually have to chop low, or it’ll simply department out and regrow.

If you wish to enable seeds to develop, don’t minimize off the flower stalk, however know that the leaves will begin to develop into extra bitter.

You can even pinch the stems again because the younger plant matures to encourage bushiness, however this isn’t required.

On the finish of the rising season, when it’s time to let your herb go to the large compost heap within the sky, pull your complete plant out, roots and all.

You understand it’s time if there’s a freeze on the horizon or if the plant retains placing out extra flower stalks than new leaves.

The place to Purchase ‘Darkish Opal’ Basil

‘Darkish Opal’ is exceptionally standard, and also you’ll discover it nearly wherever basil seeds are bought.

A square product shot of purple 'Dark Opal' basil cuttings on a wooden table.

‘Darkish Opal’

For instance, Excessive Mowing Seeds carries packets of natural seeds of this standard decorative herb.

So does True Leaf Market, which has many amount choices. Carry residence a one-and-a-half-gram packet or an ounce-, four-ounce, pound-, or five-pound pack.

If you wish to attempt a bunch of various kinds of basil, together with ‘Genovese,’ cinnamon, lemon, lime, and enormous leaf, go to Botanical Pursuits for his or her Six Basil Mix in both a gram or three-gram pack.

Managing Pests and Illness

I discover this herb to be pretty problem-free as a result of I typically develop it as an annual. Basil is technically a perennial, and in the event you develop it as such, you’ll in all probability encounter extra points.


Aphids, Japanese beetles, slugs, snails, and whiteflies will all feed on ‘Darkish Opal.’ 

A horizontal close up photo of aphids on the stalk of a dark basil plant.

Aphids are oval-shaped and whiteflies are tiny fly-like bugs in a white or grey hue. Each suck the sap from the plant and trigger harm to the foliage.

In case you discover the presence of both of those you possibly can knock them off the plant with a robust stream of water from the hose.

Spray with some neem oil or insecticidal cleaning soap if a weekly hosedown isn’t sufficient.

Be taught extra about easy methods to cope with aphids and whiteflies in our guides.

Japanese beetles (Popillia japonica), then again, aren’t really easy to handle. Whether or not the larvae, pupae, or adults are round, they may devour herbs, greens, and ornamentals with equal gusto.

Netting, insecticidal cleaning soap, helpful predators, and helpful nematodes will all be part of your Japanese beetle protection technique. Our information explains what it is advisable know.

Lastly, you’ve in all probability handled slugs and snails earlier than. Use your favourite unhazardous bait or take a look at our information to coping with these marauding mollusks for different methods.


A number of illnesses will assault basil crops and sadly they’ll take maintain quickly and show lethal.

Let’s begin with the one that may kill your seedlings earlier than they actually have a likelihood to mature.

Damping Off

I actually hate damping off. Your seedlings are coming alongside properly, and also you begin to dream of all of the dishes you’ll be whipping up topped with dramatic ‘Darkish Opal’ leaves, after which tragedy strikes.

As soon as your plant is contaminated with damping off, there’s nothing you are able to do. Your seedling goes to die. It’s sufficient to have you ever swearing off gardening.

This soilborne illness is brought on by fungal species within the Fusarium and Rhizoctonia genera, and species of water molds within the Pythium genus.

When it strikes, your crops will develop a water-soaked lesion on the base of their stems after which rapidly collapse. Generally the tops die totally, and generally they’re simply extremely stunted, however they may by no means turn into wholesome specimens.

Prevention is the one technique in coping with this illness. A giant a part of prevention is utilizing clear soil, instruments, and containers. Be taught all about damping off in our complete information.

Downy Mildew

Downy mildew is a typical illness all through the backyard. In basil, it’s brought on by the oomycete Peronospora belbahrii. This pathogen is a latest immigrant to the US, arriving in Florida in 2007, however when it strikes, it’s dangerous information.

At first, it might seem to be your plant is just a bit bit unhappy, with some yellowing foliage, slowed development, and perhaps even some faint grey fuzz on the undersides of the leaves.

Because it progresses, your complete leaf turns yellow, and the spores flip darkish grey or purple as they develop into rather more outstanding.

At this level, your plant is in serious trouble.

Luckily, ‘Darkish Opal’ and different purple cultivars are much less inclined to extreme infections, however you continue to don’t need it inflicting issues in your herb backyard.

The most effective factor to do is keep away from downy mildew within the first place.

Good air circulation, watering on the soil stage, cleansing up any fallen plant particles, watering within the morning so crops have time to dry in the course of the day, and buying seeds and begins from respected sources are all necessary techniques.

If it’s too late for prevention, you’ll must spray the leaves and stems with a fungicide.

A vertical product shot of a white spray bottle of Monterey Liquid Copper Fungicide.

Monterey Copper Fungicide

Liquid copper, like Monterey’s 32-ounce ready-to-use spray, which is accessible at Arbico Organics, is a brilliant guess.

Use it each two or three weeks till the signs subside.

Fusarium Wilt

I finished shopping for candy basil crops on the grocery retailer as a result of so a lot of them had been affected by fusarium wilt.

Crops contaminated with this illness, brought on by the fungus Fusarium oxysporum f. sp. basilici, begin to wilt as soon as they’ve reached about their mature top.

In case you take a look at the underside of the stems, you’ll see brown streaks. Because the illness advances, the leaves may begin curling and turning yellow, and generally current with brown splotches.

If circumstances are very humid or the soil is extraordinarily moist, you may even see pinkish-orange spores.

Sadly, there’s no treatment, and if this pathogen is current in your soil, it will probably stick round for over a decade. In case your ‘Darkish Opal’ is contaminated, all you are able to do is get rid of the plant and keep away from rising basil in the identical soil for at the very least ten years.


You’ll be able to harvest the leaves individually or minimize complete stems as you want them, however don’t take greater than half at a time, to permit the plant to continue to grow.

A horizontal close up of a gardener's hands collecting the leaves off of a 'Dark Opal' basil plant.

You’ll be able to pull the leaves off by hand or snip them with scissors.


Dried basil is a staple in most spice cupboards. ‘Darkish Opal’ is milder than most inexperienced leaf varieties, so it’s value preserving round for these dishes that simply want a touch of taste.

You’ll be able to find out about easy methods to dry basil in our information.

You can even freeze the leaves. First, rinse them nicely and permit them to dry. Then, lay them out in a single layer on a baking sheet and put this within the freezer.

As soon as the leaves are frozen stable, toss them in a baggie and seal all of the air out. Put this again within the freezer.

Recipes and Cooking Concepts

You need to use ‘Darkish Opal’ in the identical approach that you simply use different varieties of basil.

Purple pesto is a vibrant shock on the kitchen desk, and the leaves look fabulous with pink tomatoes, in strawberry lemonade, and marinara.

A horizontal photo of freshly harvested 'Dark Opal' basil leaves in a white pot sitting against a blue table and background.

Or how fairly would the purple leaves be in strawberry, lemon, and basil infused water? Sound good? You could find the recipe from our sister website, Foodal.

Fast Reference Rising Information

Plant Sort: Perennial herb, grown as an annual Foliage Colour: Purple
Native to: Cultivated selection Tolerance: Salt
Hardiness (USDA Zone): 4-9 (annual), 10-12 (perennial) Upkeep: Low
Season: Summer time Soil Sort: Free, wealthy, loamy
Publicity: Full solar, afternoon shade Soil pH: 6.0-7.5
Time to Maturity: 90 days Soil Drainage: Properly-draining
Spacing: 6 inches Companion Planting: Borage, marigolds, mint, nightshades
Planting Depth: 1/4 (seed), depth of root ball (transplants) Household: Lamiaceae
Peak: 18 inches Genus: Ocimum
Unfold: 10 inches Species: Basilicum
Water Wants: Average Selection: Basilicum
Widespread Pests and Illness: Aphids, Japanese beetles, slugs and snails, whiteflies; damping off, downy mildew, fusarium wilt Cultivar: Darkish Opal

‘Darkish Opal’ is a Actual Gem

It tastes unbelievable, is gorgeous sufficient to develop purely as a decorative, and is filled with antioxidants. What’s to not love about ‘Darkish Opal’ basil?

How will you utilize your plant? Is it going so as to add shade to the backyard? Or a little bit of taste to your dishes? What’s your favourite recipe? Share with us within the feedback part beneath.

And for extra details about rising basil in your backyard, take a look at these guides subsequent:

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