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How-To Guide

How to Divide and Transplant Perennials in San Diego

Crowded perennials bloom less and lose their shape. San Diego Master Gardeners divide herbaceous clumps in the fall.

Iris rhizomes sitting just above dark garden soil, with sword-shaped leaf fans and new shoots.
Iris rhizomes in a garden plot, not a San Diego bed. Photo: Jamain, Wikimedia Commons, CC BY-SA 3.0.
Now

Water a day or so before you dig, on an overcast day if you can.

Why

San Diego Master Gardeners print fall for vigor, often every two to three years.

Next

Lift the clump, keep vigorous pieces, replant the same day.

Kit

  • Spading fork or shovel (two forks if the clump is tangled)
  • Clean, sharp knife or pruners
  • Alcohol wipes or disinfecting spray (or Marin’s optional 1:9 bleach if you follow that page)
  • Compost or aged manure
  • Water source
  • Something to shade or block wind if the day turns harsh
Illustration of dividing a perennial clump: keep outer fans, discard woody center
Illustration: keep outer fans, discard woody center. Not a photograph. Not a San Diego bed.

Do this

  1. Water a day or so before you dig

    If the soil is dry, water thoroughly a day before (Marin), a day or so before (San Diego Master Gardeners), or a day or two before (Placer). Moist soil holds together when you lift the clump.

    Marin MG.

  2. Wait for overcast or rain in the forecast

    Marin says it is better to divide on an overcast day than a hot one, and that rain in the forecast is ideal. San Diego Master Gardeners print fall, not a numbered month pair.

    SD MG.

  3. Lift the whole clump, then tease or pry

    Dig down around all four sides, scoop underneath, and lift the clump with as many roots as you can. If the clump is badly tangled, Marin prints two forks back-to-back.

    SD MG.

  4. Discard diseased, woody, or less-vigorous pieces

    Keep divisions that have roots plus growing points. Discard diseased, bug-laden, woody, or less-vigorous pieces.

    SD MG.

  5. Sanitize tools the way the page you follow prints

    Marin prints an optional one-part bleach to nine-parts-water wash. San Diego Master Gardeners’ Garden Tool Care page prints alcohol wipes or a disinfecting spray, not that ratio.

    SD MG.

  6. Replant the same day into compost-amended soil

    Loosen the new spot, mix in compost or aged manure, plant as soon as possible, firm, and water thoroughly. For bearded iris only, Placer says replant with the top of the rhizome just showing.

    SD MG.

  7. Protect from too much sun, wind, and extreme temperatures

    Marin’s printed aftercare is to protect from too much sun, wind, and extreme temperatures. San Diego Master Gardeners and Placer both print pruning foliage to about six inches, except petite plants such as thyme, campanula, and lamb’s ear.

    Marin MG.

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