Basil is a herb that is much-prized for its taste and essential oils. It originates from the tropics of Africa and Asia but will live happily in subtropical regions.
Basil requires much from its environment. It needs strong sunlight and frequent watering, in well-drained, fertile soil.
It is a tender plant that is usually grown as an annual, outside of its natural environment. It is neither drought nor frost tolerant.
What would cause the basil plant to wilt?
The primary reason for a Basil wilting will be a lack of water. This could be caused by insufficient or incorrect watering, problems with the soil or root damage. Other reasons include shock, the end of the plant’s life cycle, or something more sinister, like parasites. As the plant is cultivated primarily for its leaves, an abundance of these could be detrimental to other parts of the plant. Let’s look at these issues in more depth.
Seven reasons why your basil may wilt
1. Not watering the plant enough
Basil likes to live in a warm environment which suggests that it will have a high rate of transpiration, or loss of water.
Many plants that are native to hot climates avoid moisture loss by modifying their leaves in order to reduce surface area. Not so with the Basil plant.
They have large leaves and abundant foliage when growing in the right environment. They lose moisture rapidly so they need to be watered frequently and deeply.
2. Heat dries the soil
Indoors, Basil is usually grown on a window sill that faces the sun. The heat of the sun dries out the surface of the soil and heats up the pot. The result is that moisture is lost and no longer available to the plant.
A small pot will not hold sufficient soil or moisture for a Basil plant.
3. Stem droop
If Basil is grown as an annual, its stem does not become woody and rigid enough to support significant weight.
A Basil plant, lush with leaves, might look attractive but it will put considerable strain on its immature stem and cause it to droop, giving the plant the appearance of wilting.
4. Environmental shock
If your Basil plant is exposed to a sudden change in temperature or a dramatic change in light levels, it could go into shock and shut down its systems temporarily.
This could happen if you move it to a new position in your home, when you bring it home from the nursery, or if you transplant it into a new pot.
5. End of the season
In the correct environment, Basil plants can survive for several seasons but generally they are grown as annuals. At the end of their annual cycle, the plants direct their energy towards reproduction.
Rather than feed the leaves or generate more foliage, they will produce flowers, fruit, and ultimately, seeds.
This process could give your plant the appearance of dying off.
6. Fungi and bacteria
Wilting is an advanced symptom of a parasitic invasion. The first signs will be spots forming on the leaves, leaves falling off and growing tips dying. When the infection is severe, it will affect the plant systemically and cause the leaves to wilt.
These fungi and bacteria usually get a hold on the plant when it is overwatered or allowed to remain in soggy soil. They can also form when the plant is watered on its leaves, rather than at root level.
Root-knot nematodes are microscopic cutworms that attack the plant’s roots. The damage to the roots prevents sufficient water and nutrients from reaching the leaves and causes them to wilt.
Solutions to prevent your Basil from wilting
Basil plants need constant watering during their brief growing season. Do not let the soil dry out much beyond the surface.
Water deeply. Basil plants have a dominant tap root that will grow down deep into the pot. Give the plant sufficient water to reach the growing tip of the tap root.
Shallow watering will encourage roots to grow towards the surface which will not serve the plant optimally. If you perceive that the plant is wilting due to underwatering, give it a good soaking and place it in the sun.
Water is absorbed by the roots. Drip irrigation or watering at soil surface level is best for the plant.
Do not directly spray water onto the leaves as this may encourage the growth of mildew and other fungi.
Ensure that the soil is well-drained
It is equally important not to allow the soil around the roots to become soggy. Basil likes rich, friable soil that retains moisture but does not form clay around the roots.
Most shop-bought plant pots have holes in the bottom, for drainage.
However, they also come with a pot tray that catches the water that drains out, in order to protect your home from spillage.
Excess water in the pot tray will have a similar effect to boggy soil. To avoid this occurring, you can either:
- Water the plant outside and allow it to drain before bringing it back inside
- Empty the plant tray after watering, or
- Place rocks at the bottom of the pot to separate the soil from the water.
Manage the temperature of the soil
The strong light and warm temperature that Basil enjoys will cause the soil around the pot to heat up.
Prevent this from happening by placing a mulch over the surface of the soil. This can be bark, vermiculite or any substance that does not conduct heat.
The plant needs ample soil around its roots, in order to insulate it from extreme temperatures. Place your Basil in a pot large enough to accommodate this.
Avoid using pots made from substances that conduct heat to the soil, such as metal or black plastic. Glazed ceramic pots are the best pots to use for Basil plants.
Harvest the leaves more regularly
Removing some of the leaves from the plant, will take some of the burden off the stem which will correct any tendency to droop.
Remove the growing tips
The plant’s reproduction takes place at the growing tips. By removing these regularly, the plant will not flower but produce more branches and leaves, thus prolonging the usefulness of the plant.
If you want the plant to go to seed, remove only some of the growing tips. This way, you will be able to harvest leaves for longer and allow the plant to reproduce.
Prevent fungi and other parasites
Basil plants thrive in the same environment that favours the growth of fungi. Don’t give fungi an opportunity to get established by doing the following –
- Water the plant in the morning so that it dries out to some extent before the air cools at night.
- Avoid getting water on the leaves by watering at root level.
- A layer of mulch should prevent water from splashing up onto the leaves.
- Do not harvest leaves when the plant is wet.
- Fungi live off decaying matter. Remove any dead leaves as soon as you see them.
- Spray repeatedly with a fungicide.
Dispose of the plant
If fungi or bacteria have taken hold to the extent that causes the leaves to wilt, they have already caused considerable damage to the plant.
It is best to dispose of it, along with all the soil in the pot. Do not put these on the compost heap. Disinfect the pot before reusing it.
If your plant is indoors and has been attacked by nematodes, take the same action.
If the plant is outdoors, uproot it and remove the soil around it. Cover the remaining soil with black plastic and leave it fallow for six weeks. The heat generated under the plastic will kill the nematodes.
Practise crop rotation and plant your next crop of Basil in another position.
Daniel has been a plant enthusiast for over 20 years. He owns hundreds of houseplants and prepares for the chili growing seasons yearly with great anticipation. His favorite plants are plant species in the Araceae family, such as Monstera, Philodendron, and Anthurium. He also loves gardening and is growing hot peppers, tomatoes, and many more vegetables.