How to Grow Cardinal Basil
Ocimum basilicum 'Cardinal'
Cardinal Basil is a vibrant culinary herb prized for its deep purple foliage and spicy flavor profile. Gardeners cultivate it to add visual contrast to borders while providing fresh ingredients for cooking teas, sauces, and salads throughout the warm growing season.
📷 Wikipedia: BasilStarting Cardinal Basil: indoors or direct sow?
🌾 Sow directly in the garden — Cardinal Basil is not usually started indoors.
Because Cardinal Basil cannot tolerate cold, wait until all danger of frost has passed and the soil is warm before moving seedlings outdoors or direct-sowing.
Soil, care & harvest
Prepare loose, well-draining soil with a pH between 6.0 and 7.0. As a frost-sensitive warm-season crop, start seeds indoors only after the last spring frost date when soil temperatures are consistently warm. Sow seeds shallowly at a depth of about one-quarter inch, as they germinate quickly within five to ten days under these conditions.
Space plants eight to twelve inches apart in full sun or partial shade. Keep the soil consistently moist with one to one-and-a-half inches of water weekly; mulch helps retain moisture and regulate temperature. Feed regularly since basil is a heavy feeder, ensuring robust growth before it reaches its maximum height of three feet.
Monitor for aphids, spider mites, Japanese beetles, and slugs, treating infestations with water sprays or organic controls. Prevent fungal issues like downy mildew by improving air circulation. Harvest leaves when the plant is mature but before flowering; expect to begin picking your crop between sixty-five and seventy-five days after sowing for optimal flavor.
When to Plant Cardinal Basil
Planting windows vary by USDA hardiness zone. Look up yours by ZIP code.
| Zone | Start Indoors | Direct Sow | Harvest |
|---|---|---|---|
| Zone 10 | January | — | April – December |
Companion Plants for Cardinal Basil
✓ Good companions
Repel aphids and may improve basil's essential oil production and overall flavor
Basil provides light shade for lettuce in hot weather and repels aphids that damage leafy greens
Repel nematodes and aphids while attracting beneficial insects that protect basil
Act as trap crops for aphids and cucumber beetles while attracting beneficial predatory insects
Both herbs have similar growing requirements and oregano helps repel aphids and cucumber beetles
Compatible growth habits and parsley attracts beneficial insects that help protect basil
Basil deters aphids, spider mites, and thrips that commonly attack pepper plants
Basil repels tomato hornworms and aphids while potentially improving tomato flavor
✗ Keep away from
Competes aggressively for nutrients and may inhibit basil growth through root competition
Produces allelopathic compounds that inhibit growth of basil and most other garden plants
Allelopathic properties inhibit basil growth and can stunt development
Nutrition Facts
Per 100g serving (USDA FoodData Central)
