Even though you can grow basil indoors, the herb really thrives when planted outdoors. You’ll notice the difference in the richer aroma and flavors of the leaves growing in the garden compared to those harvested from indoor-grown basil plants. Natural light and fresh air make all the difference.
Here’s a complete guide for how to grow basil outdoors.
- Basil seeds
- Organic compost
- Clear plastic sheets for cover (optional)
- Neem oil spray for pests
- Sterilized scissors
1. Choose the Variety
Basil has a lot of varieties. Each variety is suitable for a specific Growing Zone. Since you’re growing the herb outdoors, it’s important to choose the right variety for your microclimate. Buying the seeds from your local nursery ensures that the variety is suitable for your Growing Zone.
Some varieties, like purple basil, are grown for decoration. If you want a variety with a unique flavor, then either lemon basil or cinnamon basil is a good choice.
2. Select the Location
Basil favors direct sunlight, so choose a spot facing the west or south to make the most of the sun. Avoid areas that fall in the shadow of shrubs or larger plants. Also, make sure the spot is sheltered from strong winds but not fully enclosed either. Good ventilation and good airflow are crucial for the success of the herb.
3. Prepare the Soil
Wait for a couple of weeks after the threat of the last frost is over and the soil is workable. The daytime temperature should be around 70℉ while nighttime temperatures don’t drop below 50℉. Turn up the top 10 inches of the soil, and test the pH levels. Make sure the soil pH is between 6.0 and 7.5 throughout the basil’s life.
Amend the soil with perlite or coarse sand to improve drainage as necessary. Add about 10 inches of organic compost for every 2 square feet of soil, and mix it well. Allow the soil to sit in the sun for a week before planting the seeds.
4. Plant the Seeds
Plant the seeds in rows 1 foot apart and keep 2 inches between each seed. You’ll thin them out later. Sow the seeds a quarter inch deep in the soil, and cover them with a thin layer of soil. The seeds need light and heat to germinate, so keep them close to the surface. For every basil plant you want to grow, sow three seeds. Basil doesn’t have a high germination success rate.
5. Water Regularly
Water the soil immediately after sowing the seeds to get it moist. Make sure you don’t uncover the seeds while irrigating the soil. Cover the rows with clear plastic sheets to trap the heat and keep the soil moist.
Check the top 1 inch of the soil with your finger, and water the batch if it’s dry. After the seeds germinate about 7 to 10 days after planting, you can remove the plastic covers.
6. Thin Out the Seedlings
When the seedlings have three sets of true leaves, you can thin them out. Select the healthiest seedlings to keep, and pull out the rest. By the time you’re done thinning the seedlings, each basil seedling should have between 10 and 12 inches from the next seedling. Large basil varieties will require up to 24 inches of space between the seedlings.
If the temperature rises quickly and the soil dries out immediately after watering it, you can use mulch to improve moisture retention. Cover the rows with a 3-inch layer of straw or dried leaves. Make sure the mulch doesn’t touch the stem of the basil to prevent fungal infections. Mulch is also a good way to suppress weeds.
Although fertilizing is not strictly necessary for basil, the herb could benefit from sporadic fertilization during its short lifespan. Organic compost and homemade fertilizers are recommended over commercial products for non-ornamental basil varieties. If you’re growing an ornamental variety, apply a 5-10-5 fertilizer.
9. Prune the Basil
When the basil plants produce the 6th set of true leaves, you can prune the top of the plant. Use sterilized scissors or your fingers to collect the leaves above the second set of leaves. This encourages the plant to grow bushy and develop lateral stems.
10. Pinch off the Top
Around the 6th week, look for the central stem, and pinch it off with your fingers. This is the main stem that starts developing flowers early. By cutting it, you prevent the basil from wasting its resources on flowers and neglecting new leaves. If you see flowers, cut them to trigger new shoots.
11. Check for Pests and Diseases
Basil attracts regular pests such as aphids, thrips, and slugs. Hose off aphids and thrips with water, or spray them with neem oil. As for slugs, you’ll need to pick them off by hand and drown them in a bucket full of soapy water.
Keep an eye out for diseases such as powdery mildew, fusarium wilt, and basil shoot blight. Pull out infected plants, and destroy them before the infection spreads to the rest of the plants. Don’t use pesticides to treat the infections since you’ll be using the leaves of the plant in your cooking.
Once the basil plant is 8 inches tall, you can start harvesting the mature leaves. Don’t gather more than one-third of the leaves on each plant at a time. The leaves are juicy and fresh in the early morning and start to wilt as the temperature rises at noon, so harvest them in the early morning.
Tips for Growing Basil Outside
- Keep the soil moist at all times, especially as the air temperature rises.
- Water basil deeply to encourage the roots to grow deeper.
- Use mulch to improve the moisture retention of the soil.
- Check the soil pH once every 4 weeks, and amend it to bring it between 6.00 and 7.5.
- Water basil in the early morning to keep the moisture in the soil as long as possible.
- Don’t use pesticides on infected plants unless you’re growing basil as an ornamental plant.
When To Harvest Basil
Basil has a long harvest season that starts when the plant is 6 to 8 inches tall. The more you gather the leaves, the more leaves the plant will grow. The best time to harvest the fresh leaves is in the early morning before the weather heats up. Heat exhausts the plant and makes the leaves wilt and lose their juices.
As a warm-season herb, basil prefers outdoor conditions over growing indoors. Both sunlight and fresh air do wonders for the aroma and flavors of the leaves. Cinnamon basil and lemon basil are highly recommended varieties for their unique fragrances.
Ensure the plant gets 6 to 8 hours of sunlight every day, and harvest the leaves regularly when the plant reaches 6 to 8 inches tall.