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Basil plants can be bought from the store, but they’re sold on the premise of fast turnover with a lifespan of just two short weeks. It’s a longer shelf life than pre-packaged fresh basil that usually lasts just 5-days but figuring out how to keep a basil plant alive will prove trickier than you likely imagined.
Truth is, potted basil plants sold in stores are intended to have a short lifespan. They’re the consumer plant intended to be used for cooking.
It’s not like you’re buying basil from a gardening nursery that’s grown from seed, fed the right nutrients at the right intervals and grown under specific lighting conditions.
Store-bought herbs are for using, not planting, yet that’s exactly what you need to do if you’re to have any chance of figuring out how to keep basil plants alive for longer.
Give any half-decent basil plant a good start in your home, either in the kitchen or your garden and you can significantly increase the life of it and the amount of basil you can harvest from it.
Indoors, any healthy basil plant can get you around two months of fresh basil, possibly longer.
Basil Lasts Longer when You Give it Space
The first thing to do with a potted basil plant is to divide it. In almost all cases, the pot it comes in is far too overcrowded. That’s intentional because the more seeds there are in the pot, the bushier the plant is.
Store-bought potted basil usually has 10 to 20 plants crowded into the one pot. It makes it look lush, giving the allure that you’re getting loads of fresh produce with a cheap price tag.
That you are, but you’re going to have a hard time using it before the plant starts wilting, the leaves begin yellowing and ultimately, the basil plant starts withering away to nothing.
Space is the first thing to give any potted herb. For basil plants, they grow best in 4” containers with no more than 3 plants per pot. Since your average store-bought basil plant has as many as 20 plants in the one pot, you could get as many as a half dozen plants and they’ll do better once you give them the space they need to thrive.
How to Divide a Basil Plant
Dividing a basil plant is about splitting the roots with minimal damage. It’s inevitable that there’ll be some damage so the trick is to do it delicately so you do as little damage as possible.
Start by taking the pot in one hand and gently loosen the soil from the pot, avoiding handling the leaves and stems as those are extremely brittle and will snap.
Once you have the root ball out of the pot, inspect the roots. Healthy roots on a basil plant should be white. Not brown.
Brown roots are a sign of overwatering, which in the case of a new plant, usually means the soil isn’t fit for purpose as it’s not draining as it should. Discard the parts of the plant with brown roots and keep the ones with the healthy (white) roots.
Repot them in 4” plastic containers that have drainage holes and use a well-draining potting mix.
Replacing the Soil
Pre-potted basil plants rarely use soil that’s going to last a while. There’ll be enough nutrients in the soil to last a week to 2-weeks (the intended lifespan). Trying to figure out how to keep basil plant alive starts with having the right nutrients in the soil.
Basil, like most herbs, grows best in a soil that drains well and isn’t too acidic or alkaline. A pH of 6.0 to 7.0 is ideal. If you’re planting your herbs outdoors, it’s a good idea to use a soil tester to see what you’re working with and adjust the soil to suit your plants.
For planting basil in your garden, you can improve the quality of your garden soil by adding either blood meal or cottonseed meal, both of which increase the nitrogen content and help improve drainage in sandy and compact garden soil.
When growing in containers, you only need your soil to be well draining and the plant pot to have drainage holes, which prevents the roots of the plants sitting in standing water.
Common Causes of Basil Plants Dying
1 – Too Much or Too Little Watering
By far, the most frequent killer of basil plants is inadequate watering. There’s never going to be a schedule you can use to water these as they only drink what they need.
Err on the side of caution and water it less. It’s easier to add water to a thirsty plant than it is to help a drowned plant recover. The most common cause of a basil plant dying is root rot and that’s caused by too much water.
Overwatering can also be a result of the soil not draining as fast it should. Before adding water, finger test the soil and only top it up when the top inch of soil is dry to the touch.
If it’s still moist, leave it until it dries.
2 – Temperatures Dropping Too Low
Basil plants love their heat. They can’t tolerate temperatures much lower than 50oF (10oC). Garden grown basil will need to be brought indoors in the winter months, or overwintered in a greenhouse.
The ideal growing temperatures are between 80oF and 90oF (27oC to 32oC) in the daytime and not lower than 55oF overnight. It’s not always the case that low temperatures kill basil, but it’s always going to cause browning on the leaves, which is why fresh basil should be stored at room temperature and never in your fridge.
3 – Insufficient Lighting
As basil is a sun loving plant, it needs a lot of light. At least four hours of full sun daily. Depending on where you’re located, a sunny windowsill may do well, but in northern areas, you’re likely to need to supplement sunlight with artificial lighting or grow your herbs completely with grow lights without relying on sunlight at all.
4 – Overcrowding
If you’re growing your basil outdoors, perhaps in a raised garden bed, they need at least 12” of space between them otherwise each plant will compete for the nutrients in the soil. There’ll be no winner. It’s for this reason that you want to be dividing your basil plants up as soon as you get them home.
If you’re potting them up in separate containers, one pot of basil should get you four or more individual plants. If you plan to move them into the garden, make sure they’re planted at least 12” apart to prevent them from competing for nutrients from the soil.
Overcrowding doesn’t need to be just basil plants too close together. Any plants, including weeds, deplete nutrients from the soil so when you’re tending to an herb garden, you need to pay as much attention to what’s growing around your herbs, rather than just the plants you’re growing.
To Pinch or Not to Pinch Basil Plants Back?
Like a lot of plants, pruning encourages foliage growth. That’s terrific for those growing basil for cooking with, but for others who prefer to grow varieties of basil in the garden for the pungent aromas, or colorful flowers that attract beneficial insects such as butterflies and bees, pinching the plant back prevents flowering.
Whether you pinch basil back or leave it be depends on why you’re growing this herb. For cooking, it’s the leaves you want and you cannot let it flower. In fact, flower buds need to be removed as soon as they develop otherwise the leaves take on a bitter taste.
To keep your basil leaves producing an abundance of flavor, regular pinching is what’s needed, starting from when the plant is just 6-inches tall.
When a basil plant reaches 6”, the first pruning is best to be the “central stem” because that’s going to encourage new stems to branch out. Cut that back by half its size. The more stems you have, the more room there is for more leaves to grow.
When you’re pinching these back, it’s fine to go heavy because they are super-fast growers. You can pinch these back to just the two baby leaves at the base of the stem, and still grow enough for a fresh harvest in as little as two weeks.
Given how delicate the leaves are, you don’t need pruning shears to pinch them back. Just use your thumb and forefinger and give the leaves a gentle tug to remove them. The more you pinch it back, the more leaves the plant produces.
Pests and Diseases that Steal Nutrients from the Soil and the Plant
Some gardeners use basil for pest control because the strong aroma can have a repellent effect. However, fungus gnats are the exception because it’s the wetness in the soil they’re attracted to rather the foliage on the plant.
Wet soil is the ideal conditions for fungus gnats to lay their eggs. This ties back to overwatering basil and it’s another reason you want to let the soil dry out between watering.
Any eggs and larvae in the soil will die when the soil dries. Keep adding water to moist soil and the eggs can survive and you’ll struggle to get rid of the gnats.
The Japanese Beetle is about a 1/2” in size, has copper wings and it can fly. Unlike fungus gnats that are looking for wet soil to lay eggs, the Japanese Beetle eats the foliage.
They’re fond of basil and are a common pest in outdoor herb gardens. They are easy enough to spot and can be removed by hand, but if you find yourself up against an infestation, it’s best to treat your herbs with an insecticidal soap or neem oil.
Grasshoppers, in particular, younger grasshoppers that haven’t yet developed wings will linger wherever there’s a food source.
Neem oil sprays and garlic sprays can act as repellents, however, if you’re up against more than a few grasshoppers, the best course of action would be use a floating row cover to cut off access, while still maintaining sufficient light and air circulation for new growth.
Whiteflies and Aphids
Aphids and whiteflies, although different insects, both have teeth and both use those to suck the juices out the leaves on basil and similar herbs. They also lay eggs and even the eggs feed on the juices of plant leaves.
To get rid of the eggs and larvae, rinsing your plants or hosing them (gently) will dislodge eggs and larvae. Any whiteflies and aphids around the plant will be evident when they’re sprayed as they’ll fly off in a swarm.
To control winged insect populations, a popular option that doesn’t include chemicals is yellow sticky traps because a lot of winged insects including whiteflies and aphids are attracted to yellow.
You can either buy yellow sticky traps or make your own by coating a yellow piece of card with a sticky substance such as petroleum jelly or something similar that’ll have the same effect of trapping the flies when they land on the card.
Caterpillars can usually be picked off of your plants easily when you can see them as most are two to three inches long. They will feed on the leaves on the plant, and in large enough numbers, the nutrients they steal from the plant can be enough to kill a basil plant.
To prevent that from happening, the only approved chemical you can use to control caterpillar infestations is Bacillus thuringiensis. Bacillus thuringiensis kurstaki (Btk) is the strain to use to get rid of caterpillars organically.
Slugs are another garden pest that love to eat your herbs. You certainly don’t want these things leaving their slimy trail over your basil.
The problem with slugs is they’re only active at night so you’re less likely to see them and more likely to only see the damage they leave on your plant, which will always be the lower leaves only and not further up the plant.
If slugs are destroying your herb garden, see this list of options to stop slugs from eating your plants.
The most important tip about how to keep a basil plant alive is to divide it into as many smaller plants as you can. The more space there is for the roots to absorb nutrients from the soil, the more basil leaves your plant will produce.
In containers, limit the number of plants to just three per pot, and in the garden, always space each plant at least 12” apart to prevent neighboring plants and weeds from soaking up too much of the nutrients that should be going to your basil plant.