Trusty Garden Knife Divides Plants

Well-used serrated knife 

Today I am writing in tribute to the indispensible knife I use in my garden. It started life as a serrated bread knife originally purchased 20+ years ago at a discount store for $3.65, and it has served me well for all these years.

Division is economical and quickly yields a modest increase of plants for the garden. One caveat: hundreds of beautiful plants can be legally propagated, but when propagating by division, be careful to respect the plant patent rights and trademark rights of others.  If a plant is patented or trademarked it cannot legally be asexually propagated. Check the nursery label. 

large clump of daylilies

The primary use for my garden knife is the form of plant propagation known as division. Division is the dividing or breaking up of a large plant clump into multiple smaller segments, each with a shoot and some roots. These segments (known as divisions) are then replanted and each one grows into a new plant identical to the original one.

The photos illustrate plant propagation by division using an old clump of tall, maroon daylilies I'm planning to share with a friend. 

Determine where to cut

For example, if I need more Hosta for a new location, I choose an overlarge clump, carefully dig the plant, loosening the roots and lifting the plant from the soil.  I shake off extra soil so I can see the separate shoots, but I do not advise washing off the soil in water, as that turns into a muddy mess. (The hardest plant I ever divided was yellow flag Iris pseudacoris growing in the water at the edge of a pond; it was huge, heavily rooted, wet and muddy.)

slicing through the crown & roots

While some Hostas separate readily into divisions and can be teased or broken apart with my hands, others have a solid crown. With these I use my trusty garden knife to saw through the crown of the plant, creating three or four smaller sections to plant in the new spot.

Crown (white spot in soil) cut in half

Another reason to lift and divide perennials is if they become overgrown, lose vigor or produce fewer flowers. Vigorous growth typically occurs on the outer edge of the clump which has grown into new soil, while the center of the plant languishes. If I notice my daylilies are performing less well because they have gotten too crowded, I carefully fork them out of the ground, remove the soil and separate them into new divisions imagining myself to be a master surgeon. 

Trim away half of leaf surface

None of those old directions: “split apart the main clumps with a hatched, or with two spades inserted in opposite directions” for me. I -refer to investigate where the shoots arise from the crown and consider the optimum placement for each cut. Old growth from the center of the clump is generally discarded. Leaves are trimmed off to reduce water lost to transpiration.

4 vigorous divisions from original clump

Sometimes outside segments of a plant like summer garden Phlox paniculata can be removed and replanted without disturbing the rest of the plant. 

Potted up for future planting

A good rule of thumb is to divide fall-flowering perennials in spring and spring- and summer-flowering perennials in fall, after bloom. And ornamental grasses are best divided in spring because they prefer a long hot period to re-group.

Success! Now I have four strong plants in a large nursery pot to share with a friend who just bought her first house.