Mold and Mildew on Your Herbs

New growth on a Sage plant being hand-pinched
Peter Anderson/Dorling Kindersley/Getty Images

It is often said that herbs thrive on neglect. While this isn't completely true, it can be easier to find success growing herbs than with many other garden plants. One benefit is that most herbs do not suffer many of the problems that plague flowers and vegetable. Something that you could run into though is a problem with mildew or mold. Both can damage and kill even the most prolific herbs.

How to Spot Mold and Mildew on Herbs

Most herbs thrive in fairly dry conditions. They need proper ventilation and sunlight to prevent the kind of environment that produces molds and mildews. One common mistake many beginning gardeners make is overplanting. As the plants grow larger, they crowd each other and receive less air circulation and sunlight, which is vital for evaporation. Too much moisture on the leaves and stems leads to mold and mildew.

  • Mold appears on plants as a slimy, brown or black area. You will notice this on the leaf or stem.
  • Mildew is a powdery or fuzzy grayish patch. This most often occurs on the leaves but can become noticeable on the stem as well.

If you see either of these signs on your herbs, there are some emergency steps that you should take. The primary goal is to prevent more damage by eliminating conditions unfavorable to your plants.

Eliminating and Preventing Mold and Mildew

When you notice mold or mildew in your garden, it is best to act fast. An infected leaf can quickly become an infected plant and, if ignored, the problem can spread to other plants.

  • Prune off the affected area - This is as simple as pinching off the leaves where you see mold or mildew or cutting entire stems that show damage. Be sure to wash your hands before moving to a healthy plant and don't drop the moldy leaves onto the soil. Dispose of them away from your garden.
  • Thin the foliage and possibly the plants ​- This will improve air circulation, so cut down the bushiest parts of the herbs to give them more room. If necessary, move an entire plant, so its neighbors have more space to breathe. Many herbs do best if cut back regularly. Use them fresh in kitchen recipes or dry them and store them i n a cool dark cupboard for future use.
  • Water less often- You may be overwatering and inadvertently allowing the moisture-loving molds to proliferate. Don't water on a schedule. Instead, learn to recognize the signs that your garden needs water.
  • Water only the roots - Unless the summer winds are kicking up a lot of dust, do not water any part of your plants that are above ground. Water the base only and give the roots a healthy dose of water.
  • Remove the entire plant - Sometimes, removal of the plant is necessary. If you find that all of the simple changes mentioned already do not improve your herb's health, you may have to remove and relocate the plant. Consider it in quarantine and place it in a pot until it is healthy again.

Avoid Chemical Sprays and Treatments

Herbs are most often grown for adding flavor to foods, for tea, or for home remedies. You don't want to put any substance on your herbs that you don't want in your own body so avoid chemical treatments and fungicides.

While it can be tempting to run to the nursery for a chemical solution at the first signs of mold, resist the urge. Whether you plan to use your herbs fresh, or dried, the chemical compounds can linger on the plant.

Even organic fungicides are not the best solution when it comes to problems on herbs. The plants are mostly hardy and fairly resilient and a natural approach is usually pretty effective. It does require a little more work, and you do need to pay attention to your plants, but that's part of having a successful garden.

Article Sources
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  1. Shepherd, Lizz. The Complete Guide to Growing Vegetables, Flowers, Fruits, and Herbs from Containers: Everything You Need to Know Explained Simply. Atlantic Publication

  2. Millard, Elizabeth. Indoor Kitchen Gardening: Turn Your Home into a Year-Round Vegetable Garden. Cool Springs Press, 2014