Perennials that spread in mats and patches

Perennials that spread in mats and patches include yarrow, artemisias and anemones, asters, phlox, bee balms, loosestrifes, sundrops, mountain bluets, evening primroses, sweet woodruffs, spreading ferns and grasses.  Some of these perennials make good ground covers, but in a flowerbed they should be divided every few years to control their size and renew their appearance.  Mats and patches have slender stems that are horizontal and are called rhizomes.  They are located right below the surface of the soil.  The rhizomes reach out in all directions,  branching as they go and overlapping to form tangled mats.  New shoots sprout up from all parts of the mat, forming a dense patch with lots of foliage and dozens of flower stalks.

To renew a plant that you are going to replant in the same place, choose the best part of the patch, digging around it, lifting it out and setting it to the side.  Tear out the rest of the patch.  Amend the soil and replant the patch that you saved.

To start new plants without disturbing the mother patch, use a sharp spade to cut blocks or wedges about 3″-6″ from around the edge of the patch.  Lift it out, transplant and refill the hole with fresh soil.

To divide the entire patch into several new plants, cut it all into squares, lifting them one at a time, or lift the patch as a whole before cutting it.

Large divisions rarely need any special care.  If the divisions are small, just water them and watch them carefully to prevent drying out.

Check back for hints on how to divide perennials that are in clumps!