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Dividing Plants in Summer

By: Sherri Ribbey
Need to divide a perennial in summer’s heat? No sweat. Find out which plants you can divide in summer and how to do it so they take off and look great.

Can I divide plants in summer?

While spring and fall are traditionally the best time to divide, there are plenty of reasons you may need to divide a plant in the summer. Whether you’re moving or just haven’t had the time until now, many plants take summer division just fine as long as you follow the tips I’m about to share. There are even some plants, such as bearded iris and Oriental poppies, that are better off being split this time of year.

Signs your plant needs dividing:

  • Fewer flowers
  • A dead center
  • A shrinking plant

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How to divide plants in summer

1. Water beforehand

Water the plant you want to divide and its future home the day before you dig.

2. Cut back foliage

Before digging, cut the foliage back by half: This way a smaller root system won’t have to support lots of foliage in the heat later.

  • Shear plants whose leaves go all the way to the base, such as daylilies (Hemerocallis spp. and hybrids), to within a few inches of the soil line.
  • But if a plant’s leaves are mostly at the ends of the stems like Coral bells (Heuchera spp. and hybrids), you’ll need to cut individual leaves in half.

Dividing-plants-in-summer-different-root-types: As you can see here, different root types have different methods for dividing.

3. Dig up the plant & divide

Dig up the plant, slicing 4 to 6 inches out from the edge of the crown. Then you can divide. The red lines above, show you where to split the different root types. See more details on how to divide plants here.

4. Plant quickly

Get your new plant in the hole quickly so the roots don’t dry out. Once the plant is in place, fill the hole halfway with soil and water well. That way the water soaks in and doesn’t evaporate or roll off the soil’s surface.

5. Fertilize

Apply an organic liquid fertilizer, such as Neptune’s Harvest, when you water to help get plants off to a good start.

6. Finish planting

Fill the hole the rest of the way with soil and water it again.

7. Mulch

Apply an inch or two of organic mulch to help conserve water.


Tips for dividing plants in summer

  • Full-sun plants will benefit from a shade shelter for a week or two. Insert a few bamboo stakes in the soil and clothespin some landscape fabric to the stakes to make a screen. Position it on the west side of the plant to protect it during the hottest sun of the day.
  • Check your plant each day, and if it looks wilted in the morning or late evening, give it a drink of water.
  • You may need to water daily for a few days after planting.

Look over the list below and you’ll find a lot of plants that take summer division in stride. Don’t see yours on the list? Some plants don’t like division anytime. Now you know what and how to divide this summer... no sweat!

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Plants you can divide in summer

Plant name Botanical name Cold hardiness USDA Zones Plant size Root type Comments & Tips
Bearded iris
Iris hybrids
3 to 9 8-40 in. tall, 18 in. wide Rhizome Needs division every 3 to 4 years in midsummer to remain vigorous; cut leaves back so there’s 4 to 5 in. left above the rhizome
Bellflower, clustered
Campanula glomerata
3 to 9 15 in.tall, 18 in. wide Clump Divide after the first flush of blooms is finished; second, smaller rebloom will be sacrificed
Bellflower, spotted
Campanula punctata
4 to 9 26 in. tall, spreading Clump Spreads quickly; divide frequently to keep it in bounds; provide new divisions with shade
Bergenia
Bergenia cordifolia
3 to 9 8-24 in. tall, 12-24 in. wide Clump Look for fewer flowers or a crowded-looking plant; usually needs division every 4 to 5 years; cut leaves back by half
Bugleweed
Ajuga reptans
3 to 9 4-6 in. tall, 10-24 in. wide Clump Plants root as they spread; no need to dig whole plant; cut off rooted outer pieces and replant
Catmint
Nepeta x faassenii
3 to 9 12-24 in.tall, 18-36 in. wide Clump Doesn’t need division often; cut back whole plant by half so roots have less foliage to support
Columbine
Aquilegia spp. and hybrids
3 to 8 5-36 in. tall, 6-18 in. wide Woody Seedlings don’t always look like parent plant so divide hybrids every few years to keep this short-lived perennial around
Coral bells
Heuchera hybrids
3 to 9 6-18 in. tall, 10-24 in. wide Woody Don’t worry about getting roots with each piece, they’ll sprout from crown; cut individual leaves back by half to conserve moisture
Coreopsis
Coreopsis grandiflora
3 to 9 18-24 in. tall, 18-24 in. wide Clump Division every 3 to 4 years helps this short-lived perennial stay around longer; cut plant back by half
Corydalis
Corydalis lutea
5 to 8 4-18 in. tall, 6-12 in. wide Rhizome Don’t keep new plant too wet after you divide or it will rot
Daylily
Hemerocallis spp. and hybrids
3 to 9 12-36 in. tall, 9-24 in. wide Clump Divide every 5 to 7 years to keep clumps healthy; rebloomers are best lifted in spring before they flower
Dianthus
Dianthus spp. and hybrids
3 to 9 3-24 in. tall, 8-24 in. wide Clump Mat-forming types root as they grow; cut a rooted piece from the edge and replant
European wild ginger
Asarum europaeum
5 to 7 4-8 in. tall, 9-12 in. wide Rhizome Easy to dig and split; likes moist to wet soils, so keep new plants well-watered
Fernleaf bleeding heart
Dicentra eximia
3 to 9 12-18 in. tall and wide Clump Foliage may go dormant after dividing, but don’t worry, the plant will come back next spring
Foxtail lily
Eremurus stenophyllus
6 to 9 24-36 in. tall, 9-12 in. wide Woody crown Roots are brittle so only divide mature plants in midsummer; wait for the leaves to die down for the season
Garden phlox
Phlox paniculata
4 to 9 1-4 ft. tall, 1-3 ft. wide Clump Divide every 3 years or when flowering diminishes; discard the woody center and plant the edge pieces
Lamb’s ear
Stachys byzantina
4 to 8 6-18 in. tall, spreading Clump This hardy plant roots along the stem; cut a piece off the edge and replant; cut leaves back by half; don’t overwater
Lily-of-the-valley
Convallaria majalis
3 to 8 8-10 in. tall, 12-18 in. wide Rhizome Rhizomes pull apart easily; make sure each new division has a leaf and a cluster of roots
Maltese cross
Lychnis chalcedonica
3 to 9 36-48 in. tall, 18-24 in. wide Clump Divide after flowering in midsummer; cut plant back by half; may lose the second bloom
Oriental poppy
Papaver orientale
2 to 9 18-36 in. tall, 18 in. wide Woody crown Divide in midsummer; foliage goes dormant quickly after flowering so mark the plant’s location; keep new transplants watered
Perennial geranium
Geranium spp. and hybrids
4 to 9 2-4 ft. tall and wide Woody crown A ring of foliage around a dead center tells you it’s time to divide; usually every 3 to 4 years is sufficient
Peony
Paeonia spp. and hybrids
3 to 8 2-4 ft. tall and wide Clump New plants will take a few years to flower; set new plants at the same depth or they won’t bloom; keep watered
Pulmonaria
Pulmonaria hybrids
3 to 8 6-12 in. tall, 15-40 in. wide Clump Big leaves wilt easily; cut each leaf back by half and keep summer plants well-watered
Snowdrop anemone
Anemone sylvestris
3 to 9 12-18 in. tall, 6-12 in. wide Rhizome Can spread quickly in well-drained soil but more slowly in clay; cut rhizomes so each plant has one bud
Speedwell
Veronica hybrids
4 to 8 6-48 in. tall, 15-18 in. wide Clump Easy to slice into pieces; make sure to get plenty of roots with each new section
Yarrow
Achillea spp. and hybrids
3 to 10 24-36 in. tall, 15-18 in. wide Clump Divide every 2 to 3 years; cut foliage back by half so roots don’t have as much foliage to support
Published: July 29, 2020
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