Dividing in August
Divide certain perennials in August after they have finished flowering. This can prevent overcrowding, improve airflow, encourage stronger blooms, and give you extra plants for other parts of the garden.
The seven plants to divide:
- Daylilies
- Bearded iris
- Shasta daisies
- Siberian iris
- Garden phlox
- Coneflowers
- Black-eyed Susans
The general method is to water the plant the day before, dig around the whole clump, lift it carefully, divide it into healthy sections, remove old or woody centres, and replant each section at the same depth. Water the new divisions thoroughly and add a light layer of mulch, but do not cover the crowns.
After dividing, keep the plants consistently moist for several weeks and wait until spring to fertilize heavily.
General method:
- Water the plant deeply the day before.
- Dig widely around the clump to avoid damaging roots.
- Lift the whole clump.
- Divide it with a sharp spade, fork, or knife.
- Remove old, woody centres.
- Keep healthy sections with roots and shoots.
- Replant immediately at the same depth.
- Water well and mulch lightly.
- Keep the divisions moist for the first few weeks.
- Do not fertilize heavily until spring.
Plant-specific details:
- Daylilies: Cut foliage to about 6 inches, lift the clump, pull or cut it into sections with healthy roots and several fans, then replant.
- Bearded iris: Dig up the rhizomes, discard old woody centres, keep young firm rhizomes, trim leaves to 6 inches, and replant with the rhizome at the soil surface.
- Shasta daisies: Lift the clump, cut it into smaller sections, and replant 12–18 inches apart.
- Siberian iris: Lift the clump, cut the dense root mass apart with a sharp spade, and replant at the same depth.
- Garden phlox: Wait until flowering is finished, dig up the plant, slice the root ball into sections, and replant with plenty of space.
- Coneflowers: Lift the plant with a sharp spade, divide it into pieces with strong roots and stems, and replant in well-drained soil.
- Black-eyed Susans: Lift mature clumps, cut them into smaller sections with a garden knife, and replant in full sun.













