Multiply and share your perennials this fall

Gladiolus are beautiful to share with friends.

Have your favorite perennials been looking crowded and not blooming as abundantly as they used to? Maybe it is time to divide them and replant or share them with neighbors or friends. There are actually tables that will tell you how often you should divide your German bearded irises (Iris germanica), daylilies, Coreopsis, Pentstemons, Shasta Daisy, Delphiniums, Achillia (yarrow), Agapanthus and many other perennials; see this table resource for information on dividing over 100 perennials: https://docs.google.com/spreadsheets/d/1Sv07afJ8jz9h_CGA_NNdjuFcaV83BUXtT2uIsYUsNdI/edit?ts=5c478a81#gid=1250055917.
Most spring and summer blooming perennials are best divided and replanted in the fall. This is a good time because they are not blooming so energy can go to establishing roots and leaves before winter sets in. Fall bloomers can be divided in the spring. It is good to irrigate a day before digging and it may also be good to trim foliage back moderately for some plants.
Plants should be dug with a shovel or a spading fork. For very dense clumps it is sometimes necessary to use back to back spading forks to pry clumps apart after digging them out or use a hori-hori Japanese gardening knife to tease them apart or a shovel to cut them apart. Some fall perennials have spreading root systems; aster, bee balm, lamb’s ear, and purple cornflower are examples. These plants can easily be separated by hand or cut apart. Each new plant should have 3-5 vigorous shoots and discard non-vigorous plants.
Another perennial group to divide in the fall has clumping root systems that originate from a central clump with multiple growing points. This group includes astilbes, hostas, daylilies, and many ornamental grasses. Keep at least one developing eye or bud with each division. If larger plants are wanted, keep several eyes.

‘Smokerings’ is a prolific iris that will need to be divided every 3 years.

Irises have rhizomes that grow at the surface and as they get crowded, bloom less. They are usually divided every 3 years. The best time to do this is in late summer, but fall is alright too, especially if you have repeat bloomers which should be divided after blooming. Rhizomes should be lifted with a shovel, cleaned and examined. Often rhizomes older than one year without leaf fans attached are shriveled with poor roots. These should be discarded and only rhizomes that are young, healthy with roots and one or more leaf fans attached should be replanted.
Peonies and other plants having a taproot and are not easily divided. Peonies can stay in one place for a 100 years and not get crowded, but if you take care they can be divided and they must be planted at the same original depth where they previously were growing.
Dahlias are a special case that are dug and divided late in the fall. They can be dug a couple of weeks or more after frost kills the foliage. The tubers can be divided after being dug and washed or they can be washed, stored and divided later in the spring when the eyes are more evident on the tubers.
Dahlias can also be left in the ground in the Central Valley since the ground here does not freeze as in most parts of the country. In New Jersey, my mom had to dig them every fall and put them in the cellar away from killing freezing temperatures. However, they are vulnerable to rotting in wet winters here so you take your chances when not digging them. I accept that I might lose a few when I don’t dig them, but always hope my favorites will survive. After 3 years of not being dug they will likely get crowded and need to be dug and divided.
Agapanthus is another flower that will need dividing every few years or the blooms will get sparse. Instructions on how to do this can be found at: https://www.gardenandhome.co.za/gardening/how-tos/how-to-divide-agapanthus/
Gladioli are a drama flower I like and they can be dug annually or left in the ground, but if left in the ground they should be divided every two years. Dividing gladiolus will provide double the corms and double the pleasure of growing these gorgeous flowers. I used to leave a few in the ground each year to make sure I had some in bloom to enter in the County Fair Floriculture exhibit each June. I won a lot of best of show ribbons with

Best of Show-San Joaquin County Fair-2005

these beauties. Alas, the floriculture exhibits were discontinued for several years and this year although it was resumed, they had zero entries. Apparently, discontinuity is the enemy of good participation.
If you have a gardening related question you can contact the UC Master Gardeners at 209-953-6112. More information can be found on our website: http://sjmastergardeners.ucanr.edu/CONTACT_US/

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