Dark Opal Basil

Family: Lamiaceae Herb

Planting Schedule

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Sink your senses into Dark Opal Basil’s velvety, near-black leaves that unfurl with a cool, peppery-sweet aroma and a richly herbal depth.

The foliage is compact and lush, with a tender, succulent texture that holds its character beautifully when gathered fresh. Ideal for classic Italian-style pesto and fragrant garnishes, this variety brings dramatic color and aromatic punch to salads, sauces, and quick finishing touches.

Light: Full SunMaturity: 60 DaysHabit: Upright

Botanical illustration of Dark Opal Basil

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Dark Opal Basil Planting Dates by USDA Zone

Estimated US hardiness-zone windows for sow, transplant, and harvest. Enter a US ZIP above for exact local dates, or open a zone below.

Zone	Start Indoors	Sow / Transplant	Harvest
Zone 1a	Protected Environment Only
Zone 1b	Apr 20th	Jul 13th	Sep 11th – Aug 1st
Zone 2a	Apr 13th	Jul 6th	Sep 4th – Aug 29th
Zone 2b	Apr 3rd	Jun 26th	Aug 25th – Aug 25th
Zone 3a	Apr 3rd	Jun 26th	Aug 25th – Sep 1st
Zone 3b	Apr 7th	Jun 30th	Aug 29th – Sep 21st
Zone 4a	Apr 3rd	Jun 26th	Aug 25th – Sep 24th
Zone 4b	Apr 1st	Jun 24th	Aug 23rd – Sep 27th
Zone 5a	Mar 27th	Jun 19th	Aug 18th – Sep 30th
Zone 5b	Mar 23rd	Jun 15th	Aug 14th – Oct 5th
Zone 6a	Mar 20th	Jun 12th	Aug 11th – Oct 10th
Zone 6b	Mar 14th	Jun 6th	Aug 5th – Oct 16th
Zone 7a	Mar 9th	Jun 1st	Jul 31st – Oct 20th
Zone 7b	Feb 27th	May 22nd	Jul 21st – Oct 28th
Zone 8a	Feb 18th	May 13th	Jul 12th – Nov 5th
Zone 8b	Feb 9th	May 4th	Jul 3rd – Nov 12th
Zone 9a	Jan 23rd	Apr 17th	Jun 16th – Nov 26th
Zone 9b	Dec 29th	Mar 23rd	May 22nd – Dec 9th
Zone 10a	—	Oct 1st	Nov 30th – Feb 28th
Zone 10b	—	Oct 1st	Nov 30th – Feb 28th
Zone 11a	—	Oct 1st	Nov 30th – Feb 28th
Zone 11b	—	Oct 1st	Nov 30th – Feb 28th
Zone 12a	—	Oct 1st	Nov 30th – Feb 28th
Zone 12b	—	Oct 1st	Nov 30th – Feb 28th
Zone 13a	—	Oct 1st	Nov 30th – Feb 28th
Zone 13b	—	Oct 1st	Nov 30th – Feb 28th

Crop Details

Trait	Value
Days to Maturity	60
Sun Requirements	Full Sun
Growth Habit	Upright
Support Needed	None
Planting Depth	Normal
Germination Temp (°F)	70
Min Soil Temp (°F)	60
Min Night Temp (°F)	50
Harden Off (days)	10

Culinary Notes

Chef's Note

Dark Opal Basil brings a more peppery, cool-aromatic swagger than plain sweet basil, and its tender leaf mass stays intact for pesto without turning stringy or dull. Use it at the end—especially with olive oil and citrus—so that near-black, velvety aroma hits before heat flattens it.

Best Uses

classic pesto where the leaves stay lush and green-toned after pulsing
fresh torn-leaf salads and cucumber/olive oil plates that need aroma on contact
quick pan sauces and finishing oil (adds fragrance without cooking away)
garnishing soups and roasted vegetables at the end for maximum lift

Flavor Profile

cool peppery bite peppery-sweet, aromatic top notes tender succulent leaf texture deep herbal, slightly clove-like basil finish

Kitchen Pairings

Parmigiano-Reggiano Extra-virgin olive oil Garlic Lemon zest Mozzarella Pine nuts

Frequently Asked Questions

What pest or disease most often affects Ocimum basilicum (basil) and how do I fix it?

Basil commonly gets downy mildew (often starting as yellow patches on the upper leaf surface with gray-purple growth underneath). Remove affected leaves right away, improve airflow around plants, and water at the soil line (not onto leaves). If it keeps spreading, use an appropriate fungicide labeled for downy mildew on basil, and avoid re-wetting foliage for the rest of the crop cycle.

How often should I water Ocimum basilicum during peak growth, and what soil moisture should I maintain?

During the main growing phase, keep the soil consistently moist but not waterlogged—aim for lightly moist soil 1–2 inches down. Water about once every 2–4 days depending on heat, increasing frequency during hot, windy spells and reducing it if the soil stays wet. If leaves droop midday but perk up by evening, water more; if stems stay soggy or you see yellowing with mushy growth, cut back immediately.

How can I tell when Dark Opal basil (Ocimum basilicum) is ready to harvest?

Harvest when plants have reached about 6–8 inches tall and form several full sets of leaves, typically around 60 days from sowing. Take the top 2–4 inches and pinch just above a leaf pair to encourage branching, rather than cutting one large, unbranched stem. If plants begin flowering, leaves often become less tender—harvest before buds open or strip buds to keep leaf quality high.