There are a number of purple basils. Osmin purple basil is one of the most common varieties, and is a striking shade of deep purple with blue-black tones; most agree it is the darkest of the purple basils. With a spicy, clove-like flavor, it is best used fresh in salads or for garnish. The deep purple flowers can also be snipped and used in a salad.
| Common Name | Purple basil |
| Botanical Name | Ocimum basilicum |
| Family | Mint |
| Plant Type | Perennial or annual herb |
| Size | 18–24 in. tall and wide |
| Sun Exposure | Full sun (likes some shade in very hot climates) |
| Soil Type | Somewhat rich soil |
| Soil pH | 5.1–8.5 (acidic to alkaline) |
| Bloom Time | June to frost |
| Hardiness Zones | 10–11 (grown as an annual elsewhere) |
When to Plant?
This will be determined by your planting zone. There is a final frost date for each area. As a result, you can plan your gardening activities around this date. Check our Frost Dates Across North America: First & Last Frost Dates Chart. However, the date will not be the same for every plant.
How to Plant
Purple basil is easy to sow from seed and is relatively quick to germinate. When planting from seed, plant seeds about six weeks before the last frost. Purple basil is super sensitive to the cold, so whether you are transplanting seedlings from indoors or have plants in the ground, watch the early spring temperatures and cover if necessary. If you are planting a cutting or transplanting a seedling or smaller plant, make sure the ground temperature is at least 70 °F.
In addition to sowing Purple basil from seed, a cutting of basil will easily root when placed in water. Select a four-inch section of Purple basil that has not yet flowered. Roots will form within a week. Transplant the Purple basil directly into the garden or container once a healthy root system is apparent.
Plant basil among other herbs and vegetables with similar lighting and watering needs, like tomatoes or parsley. Some even say tomatoes taste better when they neighbor basil. Companions – chamomile, lettuce, peppers, and oregano. Keep a few pots of basil on the back porch to deter mosquitoes.
How to Cultivate
Purple basil is easy to sow from seed and is relatively quick to germinate. When planting from seed, plant seeds about six weeks before the last frost. Purple basil is super sensitive to the cold, so whether you are transplanting seedlings from indoors or have plants in the ground, watch the early spring temperatures and cover if necessary. If you are planting a cutting or transplanting a seedling or smaller plant, make sure the ground temperature is at least 70 °F.
In addition to sowing Purple basil from seed, a cutting of basil will easily root when placed in water. Select a four-inch section of Purple basil that has not yet flowered. Roots will form within a week. Transplant the Purple basil directly into the garden or container once a healthy root system is apparent.
How to Harvest
Purple basil does its best in well-drained, moist soil with a neutral pH. Add rich compost to the soil at the beginning of the season. Not much more soil amendment is necessary. In fact, if the soil is too rich, purple basil loses some of its flavor intensity.
Purple basil grows well in warm environments that receive about six hours of sun each day.
Give Purple basil water when the soil is dry to the touch, doing your best to water the plant at its base and not all over its leaves.
Depending upon the variety, purple basil grows anywhere from 12 to 24 inches in height. Space basil plants 12 to 16 inches apart. If you’re limited on space or only grow in containers, consider spicy globe basil, which tends to form a small, mounding habit.
Hydroponics
Germination: You can start by germinating Purple basil seeds in a paper towel or directly in the growing medium of your hydroponic system. To ensure successful germination, keep the seeds moist but not waterlogged and at a temperature of around 20-25°C (68-77°F).
pH range: The pH range for Purple basil hydroponics should be between 5.5-6.5. It is essential to monitor the pH regularly using a pH meter or pH test strips and adjust it if necessary using pH up or pH down solutions.
EC (Electrical Conductivity): The ideal EC range for Purple basil hydroponics is between 1.5-2.5 mS/cm. It is essential to monitor the EC levels of the nutrient solution regularly using an EC meter and adjust it if necessary.
PPM (Parts Per Million): The recommended PPM range for Purple basil hydroponics is between 700-1400 ppm. It is essential to monitor the PPM levels of the nutrient solution regularly using a TDS meter and adjust it if necessary.
Humidity: Purple basil prefers a humidity level of around 40-60%. You can use a humidifier or a dehumidifier to maintain the desired humidity level in your growing area.
Light hours: Purple basil requires around 12-16 hours of light per day for optimal growth. You can use grow lights such as LED, HID or fluorescent lights to provide the necessary light for your plants.
Temperature air: Purple basil grows best in a temperature range of 18-25°C (65-77°F). Ensure that your growing area is well-ventilated and the temperature is consistent.
Temperature water: The water temperature for Purple basil hydroponics is between 18-22°C (64-72°F). You can use a water heater or chiller to maintain the desired water temperature in your hydroponic system.
With these guidelines in mind, you should be well on your way to successfully growing Purple basil hydroponically. Good luck!
Common Pests and Diseases
Cercospora leaf spot (Cercospora ocimicola)
Symptoms: Circular to irregular dark spots on leaves with light centers
Cause: Fungus
Management
Avoid overhead irrigation and splashing plants with water, instead water plants from the base and apply a layer of mulch around the plants to reduce water splash; remove and destroy any symptomatic leaves; minor infections can be controlled by spraying weekly with a fungicide containing potassium bicarbonate
Downy mildew (Peronospora belbahrii)
Symptoms: Yellowing leaves; discoloration often begins around the middle vein and spreads outwards; gray fuzzy or downy growth on the lower surface of the leaves; brown to black angular necrotic patches on the plant.
Cause: Fungus
Management
Grow tolerant varieties; apply protective fungicide; ensure good air circulation around greenhouse grown plants; use drip irrigation to avoid wetting foliage.
We’ve compiled a list of videos that will teach you how to grow basil.
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