I have several LARGE Kimberly Queen ferns that need repotting. What is the best method and potting material?
The Gardener’s Answer
Hi, Judith: Kimberly Queen ferns (Nephrolepis obliterata) are beautiful sun-loving, upright sword ferns. I assume you are growing your ferns in containers, although they may not be considered tropicals in your part of the country. After a few years of growing in the same container, they will benefit from re-potting into a larger container or being root pruned and placed back into the existing container. The general rule of thumb for replanting any container plant is not to bump it up any more than 2 inches from what it is currently growing in. Root pruning is an option that will not involve purchasing all new containers. This process can be daunting for some gardeners, but it will invigorate your pot-bound plants and make them much happier in the long run. It will also prevent them from drying out so fast. Remove the ferns from the containers and shake away any excess soil. If they have a lot of excess soil, they may not need to be repotted. If the roots are on the outside of the soil ball, then it is a good thing you are giving them attention. With a clean and sharp pair of pruners, remove the smaller thread roots. You do not want to remove any of the large roots in the process, only the small thin ones. Do not remove more than one-third of the roots during this process. Then replant back into the existing container and the plant will be much happier with additional root space and less competition for nutrients as well as moisture. You may want to freshen your soil using a peat-based soil made specifically for containers. You can also give your ferns a small dose of either slow-release granular or liquid fertilizer at this time. One other option is to divide your ferns. This is exactly what is sounds like: remove them from their containers and literally make two plants out of one. Use your fingers or a pair of pruners and separate the plant from the bottom of the roots all the way up through the foliage. This will require smaller containers to replant them, but this process will also invigorate your ferns.