The Purple Basil Plant or Ocimum basilicum L.: All You Need To Know

Ocimum basilicum L., commonly known by many as “purple basil” is an easy-to-grow aromatic herb with a sweet, spicy flavor.

There are scores of basil varieties, most of which have green-colored leaves.

The Ocimum basilicum earned its nickname “purple basil” from its edible deep purple-colored leaves. Its leaves are used for culinary and also medicinal purposes.

The Purple Basil is part of the Lamiaceae family and is similar to the green basil except for its eye-catching dark purple (almost black) foliage. Their colors vary from light red to deep purple. The purple basil plant produces pink or white flowers, which adds to its beauty. Their foliage also has a more intense aroma compared to the green basil plant. 

Purple basil grows well both indoors and outdoors and can be grown in pots or directly in the ground. It is grown as an annual crop, so it is mostly grown in the summer period. Their purple appearance is a result of the high content of anthocyanin (dark blue pigments) present in the plant cells. Anthocyanin develops intensely in areas with full sunlight; therefore, the more exposed they are to full sunlight, the darker their leaves become.

Purple basil is native to the tropics of Africa, America, and Asia. They can grow to a height of 18 to 24 inches over their lifespan and perform better in a temperature range between 50 to 70 degrees Fahrenheit (10 to 21 degrees Celsius).

Scientific name	Ocimum basilicum L.
Common name	Purple Basil.
Origin	Parts of Africa, America, and Asia.
Size	18 to 24 inches in height.
Lighting	6 – 8 hours of full sunlight.
Soil	Moist but also well-draining soil.
Temperature	50 to 70 degrees Fahrenheit ( 10 to 21 degrees Celsius).
Soil pH	Acidic to slightly alkaline.
Toxicity	Not toxic.
Propagation	Propagation by cutting and seeds.

Purple Basil Varieties 

Most basil plants share similar characteristics. Purple Basil has a few varieties whose main difference lies in their foliage color. Some popular varieties include 

1. African Blue Basil.
2. Dark Opal Basil.
3. Red Ruffles Basil.
4. Red Rubin Basil.
5. Mrs. Burns’ Lemon Basil.
6. Amethyst Improved Basil.

Ocimum Basilicum Care

Light Requirements

Like most varieties of basil plants, Purple Basil needs daily access to bright, direct sunlight. They need about 8 to 10 hours of bright, direct sunlight each day. Bright light is an important ingredient responsible for the deep purple color of the purple basil plant. For darker shrubs, place them in a location with access to full sunlight.

Soil Requirements

Moist soil with a good drainage system and a pH level of around 6 to 7 is perfect for the purple basil plant. Improve the soil by adding organic nutrients, be it compost or blood meal. 

When growing in a container, use a large pot to prevent the soil from drying out quickly, and also cover the top of the soil with mulch to help retain water.

Water Requirements

Just like all the other basil varieties, purple basil requires plenty of water for steady growth. When watering, avoid watering directly on the leaves, instead, water should be sprayed on the soil. 

In warmer months, water the plant twice a week or more as needed to keep the soil moist, but not soaking wet. Mulch can also be used to cover the topsoil to retain moisture in the soil. When growing in containers, water the plant until it begins to drip through the drainage holes in the pot. 

Fertilizer Requirements

Fertilizing the purple basil is not necessary as the potting mix used in containers and compost applied directly to the soil are usually enough to provide the needed nutrients for healthy growth. Fertilizer can be applied for faster and healthier growth of the plant. 

You can use any balanced houseplant fertilizer. Add a teaspoon of the fertilizer to a gallon of water and use the mixture to water the plant. This can be done once a month.

Temperature And Humidity

Purple Basil thrives in hot weather conditions. A temperature range of 50 to 70 degrees Fahrenheit (10 to 21 degrees Celsius) is great. In colder seasons, the leaves might lose some of their dark colors as a result of low light. For plants grown in containers, move the plant indoors and place it under a grow light.

Humidity should be maintained at around 40 to 60%. In dry weather conditions, plants grown in containers should be placed indoors beside a humidifier.

Pruning

Pruning can be carried out on purple basil plants to make them bushy. Only prune when the plant has attained a height of about 6 inches. Pruning prevents the plant from developing flowers, thereby allowing the plant to focus its energy on producing more leaves.

When pruning, trim the plant down to its bottom two sets of leaves. Pruned leaves can be used for cooking and other culinary purposes.

Propagation

Propagating the purple basil plant can be done in two different ways. Either through the use of seeds or stem cutting.

For seed propagation, plant the seeds ⅛ deep in light, nourished, and well-draining soil. Sow a group of 3 to 4 seeds per hole and cover with compost. Always keep the soil warm, in a shaded location with access to bright light, and moist until germination occurs. Germination should occur between 5 and 14 days. 

For the stem cutting method, cut off a small section from an adult plant, and place the stem with the cut side submerged in a glass of water. Place it in a sunny location and also change the water every two days for freshness. After a few days, new roots should start emerging. When roots reach a height of 2 inches or more, transfer them to an already prepared soil or potting mix.

Common Health Problems/Pests And Diseases

Common pests that attack the leaves of the purple basil include aphids, Japanese beetles, slugs, and snails. Neem oil or insecticidal soap can be sprayed on the plant leaves to deter such pests from attacking.

Fusarium wilt is a common disease of the purple basil plant. Its symptoms include brown spots, leaf drops, stunted growth, etc. Currently, there is no effective remedy for Fusarium wilt. For a few years, destroy all infected plants and refrain from planting any new basil plants in that area.

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