When planting catnip seeds, the best results can be achieved through the use of proper seed preparation, adequate spacing between seed rows, and appropriate watering. As the first step, a process of freezing and refreezing catnip seeds will allow them to germinate more easily. Transplanting seedlings several inches apart in a garden bed, then thinning seedlings as necessary after they have produced two sets of leaves will help produce prime growing results. Keeping catnip seeds moist with a mister, rather than overwatering, is one key to success with these plants indoors or outdoors.
To fully prepare catnip seeds for germination, it helps to break down the tough seed coating. One way to achieve this goal is by putting seeds in a plastic baggie in the freezer for one month. Next, let the seeds thaw completely, and then freeze them for one additional month. Finally, let the seeds thaw again overnight by immersing them in warm water.
Nepeta cataria, sometimes known as catmint, can grow up to 4 feet (120 cm) high. The spacing of plants is important for successful growth. Ideally, plant catnip seeds with about 15 inches (38 cm) between rows. Transplant the seedlings outdoors to a sunny bed after the last spring frost, allowing a spacing of about 20 inches (50.8 cm) between plants.
It is important to be aware that any cats in the area are likely to be attracted to these plants, so avoid placing catnip directly adjacent to delicate plants that could be easily damaged. One way to avoid the interference of cats is to place the catnip in a hanging basket that cannot be reached by felines. Some sources indicate that birds, butterflies, and bees are also attracted to flowering catnip.
If growing catnip seeds indoors, place them initially in a warm location, such as a windowsill out of direct sunlight. When sprouts appear, move the pot to a sunnier windowsill. It is said that indoor catnip will grow best if gently stimulated with an oscillating fan for a couple of hours each day.
Catnip thrives on moist but not soggy soil. It is best to use frequent misting to maintain an appropriate level of water for catnip plants. Avoid soaking the soil. Appropriate soil alternatives for catnip seeds can include coco peat, perlite, rockwood, or vermiculite. Catnip prefers a soil pH of approximately 6.4 but will do well within a range of slightly acidic to slightly alkaline.
Like any mint, catnip will spread quickly. This can be avoided by planting potted catnip in the garden bed with soil to the rim of the pot, in order to contain its spread. Catnip will self-seed if flowers are not deadheaded. It can also be propagated via cuttings or by dividing the rootballs.