12 Cold Hardy Perennials That Prefer To Be Divided In Spring, Not Fall

Fall blooming perennials do very well when divided in spring. This gives them a longer recovery time after dividing (which can cause stress) because their growth cycle is more active later in the season. They also can get well-established in their new location before winter. Some fall-blooming perennials that thrive after being divided in spring include sedum, chrysanthemums, tall phlox, Russian sage, helenium, and Japanese anemones. 

Dividing perennials in spring is best done after the last frost date has passed. Dividing is already going to stress the plant a bit, and a hard frost might compound the situation. After the last hard frost, your late-season perennials should have already started showing a bit of spring growth. Some, like leadwort, are slower to wake up and you have to know where they're located to dig up the roots for dividing.

To lower the amount of stress to the plant being divided, start by watering the root system lightly, or wait until after it has rained. This moisture is soothing to the plant and will make the soil softer and easier to dig. Handle the roots gently when pulling them apart. If you need to cut the roots to divide them, use a flat-edged shovel or garden knife and cut as cleanly as possible. Replant divisions quickly. Wrap them loosely in slightly damp paper if you need to wait a day or two.

Chrysanthemums are the classic autumn-blooming perennial. Plant them in spring to give them time to establish themselves, then divide them every two or three years to multiply their beauty. Planted properly, potted mums will return each year. Mums bloom best in full sun, and they like rich, well-drained soil and plenty of water during their growth season. To divide in spring, gently cut the woody roots and water well in their new spot. Some gorgeous varieties to try are 'Whippoorwill' (pale peach), 'Jessica Louise' (pink with gold centers), 'Royal Glamour' (reddish coral), and 'Coppersmith' (deep bronze orange).

Also known as sneezewort, helenium is a tall, gorgeous perennial topped with colorful daisy-like flowers in a range of warm shades. They attract many pollinators, and aren't fussy about soil. Plant them in a sunny spot at the back of the border and give them plenty of water. The root system is woody but not too dense, and can be divided in spring as soon as green shoots appear. Try one of these vibrant cultivars: 'Red Jewel' (rose pink), 'Moerheim Beauty' (bright red and bronze), 'Mardi Gras' (orange with yellow edges), and 'Mariachi Salsa' (light to dark orange).

This charming fall-blooming perennial adds soft pastel shades of pink and creamy white to the autumn garden palette. The nodding daisy like flowers rise on tall stems above deep green leaves, and bloom nicely in partial shade areas. Some Japanese anemones spread freely by reseeding through the garden, while others stay more contained. They can be divided at the base by gently pulling the roots apart. This is best done in spring as the plants emerge, usually in mid-April. Like other types of anemone flowers, Japanese anemones like moist, rich soil.

This low-growing perennial is a blue-flowering plant that adds vibrant color to the autumn flower bed. Ceratostigma plumbaginoides, also known as leadwort, hardy plumbago, and peacock plumbago flowers from late August through September, with green leaves that turn reddish bronze in October. This plant works well near early spring bulbs like daffodils and hyacinths, as it starts growing just as their foliage is dying back. Leadwort is cold hardy, deer resistant, not fussy about soil, and blooms best in full sun. The loose root system is easy to divide and replant when it emerges slowly in late spring.

Perennial ageratum (taller than its annual version) is also known as mist flower. The small, button-shaped fuzzy blooms come in periwinkle blue, reddish purple, and white, and they grow to about two feet tall. They tend to spread in the garden, but their thin white roots are easy to pull up and remove. Since they emerge slowly in spring, you can see them coming up and divide them as you wish. Not fussy about soil, they bloom in partial to full sun. They add brilliant patches of easy color and feathery texture in the autumn garden.

Agastache, also called hummingbird mint, is well-loved by many pollinators. The fragrant, colorful flower spikes attract bees, butterflies, and hummingbirds. These charming plants look great in a cottage garden. They grow in clumps and perform best when divided every three to five years. The root clumps can be divided in spring with a shovel or sharp garden knife. Agastache is resistant to deer and rabbits, drought tolerant, and blooms in partial to full sun. It comes in a wide range of colors, including pink, blue, purple, and orange.