QUESTION: Do herbs need deep pots? I’d like to grow some herbs, but I don’t have a yard and I already have some smaller pots I could use. — Leanna F
ANSWER: The size of the pot or container an herb plant requires will depend on the size of the plant itself. As plants mature, they’ll get larger and eventually outgrow their containers, needing to be transplanted to larger pots as time goes on. Plants at the nursery tend to have been in their pots too long, so when you purchase a new plant, it’s a good idea to double its container size right away. Keep in mind that plants in deep pots need to be watered less frequently than those in shallower pots. All containers you use in the garden need to have drainage holes.
At a bare minimum, pots for growing herbs should be six inches in diameter. Six-inch pots are really only suited for dwarf plants, thyme, and globe basil, and you’ll need to water plants in these small pots frequently, so you may wish to scale up and use something larger. Eight- or 10-inch pots work well for most varieties of herb plants. Twelve- or 18-inch pots work well for parsley, basil, lemongrass, and any herb plant that’s grown very large as it’s matured. You’ll also want to use 12- to 18-inch pots when you group more than one plant together.
Chive plants have the shallowest roots of all herbs at just three inches long. Parsley and basil in particular have deep roots and do better in containers at least 18 inches deep. Oregano, tarragon, and thyme have root systems that are six inches long. Cilantro and summer savory have eight-inch roots, and rosemary needs 12 inches for its root system.
Even if you’re starting out with baby plants whose root systems aren’t fully developed, it’s a good idea to plant them in a container that will accommodate the eventual root size so you don’t have to transplant them to a larger pot too soon.