According to Greg Pongetti, the Living Collections curator at the California State University Fullerton Arboretum, herbs need rich, well-draining soil in order to grow well. “Herbs do not like their roots to be constantly wet, so if your soil drains poorly, they are likely to die,” he says.
You can test your outdoor soil drainage by digging a hole about 1-foot deep and 1-foot across. Fill the hole with water, wait 12 hours, and then fill it with water again. This time around, set a timer and see how long it takes for the soil to absorb the water.
Well-draining soil should soak it up in under two to three hours. If yours doesn’t drain quickly, you might want to bring some bagged soil into your garden that’s specifically for herbs and vegetables.
If you’re growing directly in your garden’s own soil, Pongetti adds that it’s a good idea to “amend” the soil by mixing in 1 to 2 inches of compost into its top layer before planting to help ensure your herbs will thrive.
If you don’t have a spacious yard or patio and are limited to a porch or balcony, you may prefer to plant your herb garden in pots. This is also a better choice if your garden area doesn’t receive sufficient sunlight.
“Use a high-quality potting mix to fill your containers,” recommends Enfield.
Most herbs can grow in a limited space, making it easy to experiment and have a variety of herbs within reach. “An 18-inch container has enough growing space for around five herbs, and a 14-inch container will successfully hold about three plants,” says Enfield.