Basil roots grow to around 8-12 inches when the plant is full sized. Basil stems can grow as tall as 3 feet and will grow their root deep to support the plant and absorb nutrients and water from deeper in the soil. Choose a pot or container that is around 10 inches deep to give your basil plants plenty of room to grow their roots.
Basil plants grow well in raised garden beds that are at least 12 inches so they can grow to full size. Basil plants can be kept smaller by trimming the stems regularly. This will result in sweeter leaves and softer stems.
Deep watering is important to grow strong basil plants and encourage their roots to grow deep and become more drought tolerant. Watering basil every 2-3 days deeply in summer is better than a small amount each day.
Do basil have deep roots?
Basil will have roots that are around 10 inches deep once the plant reaches full size. A seedling that is only 3 inches tall still has a deep root system that is already growing down to around 3 inches reaching to the bottom of the small pot.
Basil plants are ready to be planted out from their pots when you can see the roots coming out of the bottom of its growing pot. These basil plants look tiny but are ready to go out into the garden bed or a new pot.
Pot depth for basil plants
When choosing a pot for your basil it is best to choose one that is deep enough for the full depth of the roots. A container that is 10 inches deep will allow the basil to grow to full size.
To keep the basil small however a 5 inch pot can be used. The plant will still grow well and can be kept small or replaced after 1-2 months. A basil plant will grow back after pruning so you can keep a small pot on your kitchen windowsill to pick each day.
Planter box depth for basil
A planter box is perfect for growing basil as most will be at lest 10 inches deep. My planter box is closer to 18 inches deep and is deep enough to grow tomatoes, chilis and any other herbs or greens. I have mixed basil through with chilis, strawberries and tomatoes this year and all are growing well together.
Can I grow basil in a grow bag?
Grow bags a perfectly good way to grow basil at home. Plant basil in a small grow bag with some parsley or chives or choose a bigger bag and grow it together with tomatoes. Grow bags are perfect for annual plants like basil and will be deep enough to keep their roots happy.
Basil will be able to reach its root down deep and keep it feed with nutrients and water. Basil and tomatoes love full sun so move the grow bag around to get the most sun you can. Basil, tomatoes, parsley and chives all love the same conditions with regular water, full sun and a warm, summer growing season.
Plant a mix of herbs and vegetables together to create a diverse planting mix to confuse passing pest insects.
Does basil like to be root bound?
Basil will survive being root bound but will not grow to its maximum height or size in shallow soil. Basil will grow to its full size when it is in soil depths that are at least 8-12 inches.
Basil plants can be trimmed regularly to keep them to a small size and fit in a pot that is as small as 4 inches. While the plant will not last as long or grow as big as basil grown in deeper soil it will still give you plenty of basil over the summer.
Basil plants can be replaced with new seedlings every 4 weeks for a continuous supply of leaves or planted out in your garden bed to give them more room to grow.
How to fill a container or pot for basil
Basil loves to grow deep roots in free draining, organic matter-rich soil. Plant out basil in improved soil in garden beds with added aged cow manure and compost. Add a handful of pelleted chicken manure 4 weeks after planting basil out into improved soil or add some liquid nitrogen fertilizer like fish emulsion.
Plant basil into good quality potting soil if you are planting them into a pot or container. Potting soil made for vegetables or a premium potting mix will contain slow release fertilizer to keep the basil happy for at least the first 4 weeks. Keep the plant watered regularly and add pelleted chicken manure to give them a nitrogen boost.
Should I trim long basil roots?
When you buy basil from a supermarket or from a nursery the plant usually will be at its maximum size for the pot that it is in. This is really common for supermarket herbs as they want them large and ready to pick when you buy them.
This is why it can be tricky to transplant supermarket herbs as they can be pot bound. The roots can be tangled and there will be very little soil room left. Basil roots that are tangled can be gently pulled apart to give the roots more room to move when you are transplanting them.
You can trim off any of the basil roots that are dangling beyond the pot. Pull the plant apart into 2-4 pieces and replant them into a pot with new potting soil or into a raised garden bed. Water the basil well for the first few days to get it settled in and this will give a pot bound plant the best chance of recovery.
How deep do basil roots grow? | Summary
Basil roots will usually grow to around 8 inches deep but can be kept smaller by regularly trimming the top of the plant. Basil plants will survive for a few weeks in small pots but to grow them bigger they will need more soil depth.
To grow large basil plants grow them outdoors in a garden bed or raised vegetable garden. For smaller basil plants, try a cute self-watering pot and place them on your windowsill. The plant may become pot bound after a while but can be replaced with a new one throughout the season.
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I am an accredited practicing dietitian, experienced gardener and a dedicated cook. I love writing and sharing my experience so you can learn from my successes and mistakes.