If you're tired of paying big bucks for small pots of perennials of dubious hardiness, look around your garden (while you're lying in the summer hammock) and choose the flowers that perform best for you.
In northern states, August is the best month to divide perennials because the ground is warm and the sun high, so with water the transplants can develop a good root system before winter. Most will flower next year.
It's best to hold the digging until they have finished flowering, so one usually starts with the earlier blooming varieties. And though each flower has it's own little idiosyncrasies, most respond to plain old fashioned replanting.
Which means: Dig a good deep hole. Enrich the soil with compost, superphosphate, lime and maybe a little manure in the bottom if you have it. Don't skimp on this soil preparation for it is the secret of future longevity and success.
Then dig the perennial to be divided. Gently separate it, keeping the roots attached to each shoot. (Most clumps have natural divisions.)
Carefully replant in the new soil, firming them by pressing the soil around each plant. Make sure it's set at exactly the same level it was growing. Better higher than too low and smothered.
Make a well around it and water twice, preferably with half strength liquid fertilizer to encourage new root growth. If the sun is hot, provide shade with a paper bag or big flowerpot for several days.
Water weekly (no more fertilizer) until mid-September, then drastically cut back the water so the plants can harden off before winter. Mulch if possible during winter. Fertilize with 10-10-10 or similar in early spring before growth starts.
And that's all there is too it. Well almost.
But there are some caveats:
- Divide only big overgrown clumps if you want them to bloom next year. Plant 3 -5 strong shoots in each new clump for earlier bloom, particularly hosta and daylilies. Single shoots will grow as well, but may take longer to reach blooming size.
- Easy to divide and multiply perennials are yarrow, ajuga, columbine, campanula, daisy, lily of the valley, coreopsis, pinks, daylily, mallow, iris, beebalm, sundrops, sedum, coral bells and phlox.
It's interesting that if phlox is dug in late summer or early fall, a circle of new plants will arise next spring from the root tips that remain. This does not happen with spring transplanting.
- More difficult and dividing often delays bloom for a couple of years, particularly peonies, poppies, balloonflower, hosta and bleeding heart.