Considerations for container gardening
Containers need more frequent watering than garden soil. This leaches the nutrients out of the root zone faster. The smaller amount of soil in containers also holds fewer nutrients. Fertilizer at a lesser amount, more often, to compensate.
Considerations for herb gardening
Fertilize lightly. Too much fertilizer makes plants grow too quickly. Rapid growth reduces the concentration of essential oils in the leaves of fresh herbs, resulting in less flavor.
Do not get fertilizer on leaves. This can burn the foliage.
Avoid using compost, compost teas, or fish emulsions on your herb plants. They are popular and work well in a traditional vegetable garden or with other container plants. However, they don’t provide the range of nutrients needed when you grow herbs in containers.
Considerations when using potting soil
Most commercial potting soils have fertilizers in them. Wait for 4-6 weeks after potting herbs to begin fertilizing. This gives the plant time to deplete nutrients from the growing media.
Do not apply granular fertilizers when the potting mix is dry. This can damage the root system. Water them in well to move nutrients throughout the container.