|Petunias under Dark Towers Penstemon|
Before a plant takes over its allotted space and before it falls over from outgrowing its core, take a look at where you could transplant pieces of it where the root cuttings would thrive.
At this time of year - after booms have faded in late summer and early fall - you can prune back the entire plant before digging, dividing, and transplanting.
After pruning, use a shovel, fork or trowel to cut all the way around the plant's root ball.
If the plant is woody and large, digging down far enough may require digging out a trench where you can get enough leverage to lift the roots without too much damage. Outside the drip line is the place to start. The outermost tip of the leaves where rain drips off is the drip line.
Perennials make roots in the winter and stems in the spring and summer so dividing and transplanting now will give them ample opportunity to become established before winter dormancy arrives.
Plan to replant the same day or at least the same week. In between digging and transplanting, keep the roots damp with newsprint or compost.
Prepare the new planting spots by adding compost, peat, coir, worm castings, or other soil conditioners such as one-third potting soil.
Use a shovel, knife or pruning shears to cut the plant into at least 4 or 5 clumps. Rinse the dirt off the roots so you can see where to make the logical cuts. Look for crowns, offshoots, offsets, and other natural dividing places.
Plant the best bits. Clean out anything dead or funky looking. Put the healthiest looking roots into the soil and the rest onto your compost pile.
Make the new planting holes large enough to hold the roots rather than sticking the cutting in any old place you can tuck it. Expect each cutting to become as large as the entire plant you just dug up and leave that much space for it.
Well prepared and amended planting soil will make your transplants grow into healthy perennials. No fertilizer needed right now.
For a complete list of what to divide when, go to this Fine Gardening article
Text and demonstration videos: Janet Macunovich, Photos: Steven Nikkila and
What to divide when and how: Todd Meier
In my photo is my well-loved Penstemon Dark Towers which I divide late summer or fall.
Deer and bunny resistant, reliable flowers attract butterflies, medium growth rate (not aggressive), average to dry soil is fine, American native, sun or part sun, can be used as cut flower.
According to Gerald Klingaman, Dark Towers Penstemon is superior to Husker Red (perennial plant of 1996) because it is stronger and needs no staking. Read all about Dark Towers in Klingaman's article for the Univ of Arkansas Extension here.