Spring is the Time to Divide Perennials
By Dennis L. Patton, M.S., County Horticulture Agent, K-State Research and Extension/Johnson County
One of the biggest springtime chores is dividing perennials.
Perennials are plants that return each spring for another year of growth. Some types are very slow growing, such as peonies, which rarely need to be divided. Others, such as monarda, spread like weeds from one season to the next and must be kept in check.
Besides plants outgrowing their allotted space, there are a few other ways to tell when it is time to divide. Often plants in need of division will bloom less. As clumps become overcrowded they produce less blooms. Also, many older clumps of plants will develop an open center or a donut pattern. The new growth comes from around the outside of the clump as the middle dies out.
So, if your plant has out grown its space, is flowering less or has an open center, it is time to divide. The ideal time to divide is in the early spring just as growth begins and while the temperatures are cooler. The exception to this rule is iris and peonies. They are best divided at other times of the year.
There is no easy way to divide a large clump but to just do it. Either the whole plant can be lifted and broken apart, or wedges can be removed while leaving just enough of the plant in the hole to renew the clump.
Many perennials have a very thick, fleshy root system. The best way to divide is to work the clump apart into smaller sections that contain around three to five growing points. Avoid too large of divisions, or you will be dividing again soon. Some plants must be cut apart. A sharp short spade or a butcher knife can be used for this process.
After the plant is divided, a division can be put back into the hole. This is also a good time to add some organic matter or compost to the soil for improvements. You will also find that you have extras. These are great to share with friends and neighbors or just simply throw them away.