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Why are Basil Stems Turning Brown?

Are you troubled by the ghastly sight of basil plant stems turning brown with a mushy texture and pungent smell?

The sight of brown, mushy stems on a considerably young basil plant indicates root rot.

However, do not be alarmed yet as many other factors could cause browning basil stems.

Basil plant stems turn brown and mushy when suffering from fungus rot. However, letting the plant blossom and leaving them in the cold may also cause brown, woody stems.

Holy Basil Stem
Holy Basil Stem (Source: Wikimedia)

There are many instances where basil plant stems may start browning, caused by many factors.

Therefore, as a new grower, you must keep an eye out for your basil plant to ensure the browning stem is not an alarming indication.

Is it Normal for Basil Stem to Turn Brown?

Basils (Ocimum basilicum) are annuals that flower once every growing season and become dormant in winter.

Although not normal, there are instances when basil stems will start browning and turn mushy or woody in texture.

When the temperature starts dipping, usually below 50-degrees, the plant stem will become woody to protect itself from the cold stress.

Brown Basil shoots
Brown Basil shoots (Source: PSU.edu)

It is normal to see slightly browning and woody basil stems in winter, so do not worry and bring it inside.

In addition, a plant that has blossomed will also start producing brown, woody stems, where the blossoming indicates that they have stopped growing and entered a reproduction phase.

However, if none of these scenarios are present when your basil stems start browning, it may be an indication of something much graver.

A browning stem with a mushy texture, sometimes combined with a foul smell, indicates a stressed plant suffering from root rot problems.

Remember, basil does not like being watered too often and hates sitting in too much moisture, which invites fusarium bacterium.

Fusairum Oxysporum
Fusarium oxysporum (Source: Wikimedia)

A basil plant infected with fusarium bacterium will soon lose a healthy set of roots, causing premature browning and decaying of stems.

Therefore, an exceptional browning of stems on a favorably young basil plant may highlight a grave issue of root rots.

Why is Basil Stem Turning Brown?

As previously mentioned, a basil stem may start turning brown for many different reasons.

Although most of the scenarios are harmless to the plant, root rot could be a serious concern.

However, you can quickly treat the browning stem problems with immediate intervention.

Let us look at the different scenarios of the basil stem turning brown and treat them.

1. Blossomed Basil Plant

Although it may sound unusual, a blossomed basil plant blossom will eventually produce brown, woody stems.

While basil flowers look lovely and have equally nutritional benefits, they are rarely ever grown because they kill the plant.

Blooming Basil
Blooming Basil (Source: Pixabay)

Once you let it flower, the plant invests all of its energy towards producing seeds.

The plant stems start turning brown and woody to help preserve more energy and redirect the seeds (reproduction phase).

The flowers primarily give out seeds that may be useful for resowing, but it will adversely affect the leaves’ flavor, causing a loss in their signature aroma.

Dried basil Twigs
Dried basil flowers (Source: Pixabay.com)

Therefore, if you are growing the plant primarily for its leaves, you should prevent it from flowering.

Although you cannot revert the reproduction stage to the growth stage, you can minimize the damages.

Solutions

  • Start with harvesting all the flowers immediately so that your plant can redirect its energy towards the stems.
  • Harvest leaves from a different section of the plant to reduce foliage.
  • Cut overgrown stems about 3-inches above the ground or about 1/4 inch above the bottom set of leaves.
  • Remove stems that have started to become woody.
  • Feed your plant every 4-6 weeks with a 12-10-10 solution to encourage foliage growth. (A slightly higher nitrogen content will help boost foliage growth)

One of the Quora users highlights in his answer;

Do not allow the plant to bloom if you wish it to continue producing foliage, and you may want to plant a few seeds at this time and start some fresh plants.

2. Winter-stressed Plant

A winter-stressed basil plant is equally prone to producing brown, woody stems or barks.

The plants that are left to die in the cold will therefore stimulate the development of woody stems as a defense mechanism.

Woody basil plants with yellowing foliage indicate they are protecting themselves from the dipping temperature, anything below 50°F.

Yellowing Basil Leaves
Yellowing Basil Leaves (Source: Pixabay)

The next time you find your basil plants growing woody stems before winter, immediately move them inside.

The plant growth naturally subsides in the winter, but you would still find some green foliage to harvest.

The dormant plant will come back to life when adequately cared for in the next growing season.

Read our article on harvesting your basil plant without killing the plant.

Solutions

  • Move your basil plant away from areas like patio, terrace, and window that directly get cold air blasts.
  • Ensure to place them in an area that receives 6-8 hours of sunlight every day. Otherwise, keep them under the LED grow light for 12 hours each day.
  • Keep the indoors preferably warmer between 50°F–80°F by using a heating pad, central heating, or warm HID grow lights.
  • However, avoid placing them close to the heater or AC units as it can suck the plant dry. Ensure to keep the humidity level between 40-60%.

3. Root Rot

A basil plant grown in poor conditions, especially extremely wet soil or moist surrounding, may attract fungal infection.

Fusarium oxysporum is a fungus endemic to basil plants. They enter plants through their roots by invading the nutrient and water transporting xylem tissues.

The fusarium basilicas proliferate with the rise in wet soil conditions in indoor basil plants.

An example of Fusairum rot
An example of Fusarium rot (Source: University of Minnesota)

A study indicates that a well-known soil-borne plant pathogen consists of many plant-associated fungal species that severely damage plants, eliciting chlorosis, necrosis, premature leaf drop, and browning of the vascular system.

Once infected, the root system will start rotting, causing basil stems to start browning at the bottom and turn mushy.

It is one of the early indications of root rot.

Check for other tell-tale signs of slowing growth and yellowing leaves in your basil plant.

The stem will turn brown and black with a mushy texture that gives a pungent smell in a severe infestation.

According to a report prepared by the University of Illinois Extension, there is no cure for basil Fusarium wilt once symptoms are apparent. Always infected plants should be removed immediately.

Solutions

  • Try leaving the plant under direct sunlight for at least 6-8 hours a few days or using BLITOX Copper OXY fungicide containing copper oxychloride to help treat mild infestations.
  • If symptoms persist, consider entirely disposing of the plant and potting soil and sanitize the container before reusing.
  • To prevent the risk of fusarium, buy basil seeds that have been tested for the Fusarium wilt fungus.

How to Prevent Basil Stem from Browning?

Preventing basil stem from browning is relatively simple but may require regular inspection and utmost care.

Here are a few preventive measures to keep your basil stems from browning.

1. Regularly Prune the Plant

  • Harvest basil leaves and trim the plant-top regularly during the growing season.
  • Pick leaves from each plant stem for even harvesting, but leave at least one-pair leaf on each branch to prevent overgrowth of spindly branches.
  • Trim skinny, overgrown, and brownish outer stems to allow the sunlight to reach inner branches.
  • Prune grouped foliage that appears on top of the plant to prevent it from turning into a flower.
  • Remove any visible flower buds as soon as they appear.

Consider drying and storing harvested flower buds to keep them preserved for later uses.

2. Protect from Cold

  • Remove your plant from places that get cold drafts like windows and patios, especially in the fall.
  • Move them inside the house when the temperature starts dipping below 50-degrees, usually during fall and winter.
  • Employ mechanical ways to boost warm air by arranging HID grow bulbs or central heating.
  • Alternatively, place heat mats under the plant container to help keep the soil warm.

3. Prevent Wet Conditions

  • Basil plant hates being overwatered. Keeping watering to 7-10 days in the growing season and cut back on watering to 2 weeks or more in the winter.
  • Check whether the top few inches of soil have dried before watering the plant.
  • Do not let the plant sit on the water. Instead, collect drained water on a saucer and throw it away immediately.
  • Avoid moist conditions by removing your plant from damp, wet corners.
  • Arrange them in well-aerated, humid areas near the window or close to the bathroom.
  • Provide at least 6-8 hours of sunlight or 12 hours of grow light every day.
  • Use containers made from a porous material like terracotta and unglazed container to help evaporate excess moisture.

What are the Uses of Woody Basil Stems?

If you assume that woody basil stems are useless, you are wrong. On the contrary, the basil stems contain a significant amount of vitamins and antioxidants.

Although dry and hard to chew, you can use them as food condiments or infuse them in oil for salad and pizza dressings.

In addition, you can harvest the leaves from the woody stems as usual.

Here are some of the beneficial uses of dried basil stems.

  1. Infuse with Oil or Vinegar -Cut the dried basil stems and submerge them in a neutral oil or white vinegar bottle to use a salad dressing.
  2. Add to Stock -Break dried twigs into pieces and tie them with kitchen twine to make a sachet. Now drop them into stock and bring to boil. Remove them before using the stock.
  3. Blend into Paste -Put leaves and dried stem into a food processor and add the blended mixture to make chimichurri, pesto, or any blended sauce.
  4. BBQ Seasoning -Break the dried twigs and them onto the coals for herb-infused smoke.
Basil leaves into olive oil
Storing Basil leaves and stems into olive oil (Source: Unsplash.com)

Conclusion

Keep in mind, basil plant is sensitive to changes in weather and growing conditions, and the growing brown, woody stem is its way of showing problems.

An adequately warm and well-lit location with watering once in 7-10 days is essential to help keep your basil plants healthy.

Moreover, ensure to harvest its leaves and prune every two weeks in the growing season to prevent blossoms.

Related Article: How to Grow Lime Basil from Seeds?

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