When to Plant Sedum: Spring or Fall Planting, Dividing, Cuttings and the Chelsea Chop for Upright Stonecrop

The tall "sedums" sold as 'Autumn Joy', 'Autumn Fire' and 'Matrona' now belong to the genus Hylotelephium, though most tags and gardeners still call them sedum or stonecrop (RHS, Nebraska Extension, UC Master Gardeners). Showy stonecrop (H. spectabile) is a clumping succulent native to China and Korea that forms a mound 1 to 2 feet high and wide (NC State). Its flat heads of small star-shaped flowers open in late summer and fall, and 'Autumn Joy' blooms for about 6 weeks from late August (UC Master Gardeners). This guide covers the upright types; the low, creeping stonecrops are grown as ground covers (Almanac).

When to plant sedum

Use our planting calendar to see your frost dates. Sources split on the best season: the Almanac favors spring, between the last frost and the summer heat, while the RHS puts autumn first and spring second. Our reading is that spring is the safer choice where winters are cold and wet, and early fall works in milder areas, as long as new plants are watered for the rest of the season (RHS). Most upright sedum is bought as potted plants, cuttings or divisions rather than grown from seed (Almanac), and named cultivars do not come true from seed, so we cover those routes here.

How to plant sedum

Iowa State divides clumps with a sharp knife, keeping several shoots and some roots on each piece, and replants right away. Rooting a cutting is just as easy: NC State says the plant can regrow from a single leaf, and the RHS notes that rooted shoots sometimes break off the base in late winter and can be planted out.

Watering, pinching and staking

• Water until established. The RHS waters for the first few months; after that, rain is usually enough (RHS, Almanac). UC waits until the soil is dry a few inches down.
• Don't feed. The RHS says sedum needs little or no fertilizer, and extra nitrogen gives floppy, disease-prone growth.
• Chop for sturdier stems. The RHS cuts new stems back by half in late May; NC State pinches in early spring and warns that summer pruning delays bloom; UC cuts floppy stems by half before buds form.
• Flopping means too much. Too much water, fertilizer or shade is the usual cause (Nebraska, UC). Tie stems to stakes if needed (UC).
• Divide when the clump of buds at the base gets wide (UC), in early spring (Iowa State).

Sedum in containers

NC State lists outdoor containers among its uses, and the RHS grows it in pots but says potted plants need regular watering because their roots can't reach deeper moisture. The RHS also warns that vine weevil grubs can damage roots in containers. Our reading is to use a gritty, free-draining mix in a pot with drainage holes and to water whenever the top inch dries (GardenPal reasoning).

Fall and winter

• Leave the seed heads. UC, the RHS and the Almanac leave dried flower heads for winter interest; UC says birds pick seed from them, and the RHS says the old stems shelter ladybirds and lacewings.
• Cut back in late winter or spring. The RHS cuts dead stems to the ground in spring as new shoots appear, and UC breaks them off where the new buds are forming.
• Wet soil is the winter risk. The RHS says plants can rot in soil that stays wet all winter, though they are often surprisingly tough.

Pests and problems

Rot in wet, poorly drained soil is the main problem (NC State, RHS, Nebraska). NC State lists aphids, mealybugs, nematodes, scale, slugs and weevils; the RHS adds slugs and snails on soft growth and occasional powdery mildew in very dry soil, which it calls cosmetic. UC sees black aphids mostly on sedum grown in too much shade and knocks them off with a strong spray of water. Sources disagree on deer: NC State says stonecrop resists rabbits but not deer, UC says deer often eat it in fall despite its place on deer-resistant lists, and the RHS and Almanac also report browsing. They also disagree on toxicity: NC State tags it as a plant with low-severity poison characteristics, while the Almanac lists sedum as non-toxic, so keep it away from pets and children who chew plants if in doubt.

Sedum around the vegetable garden

Upright sedum blooms late, when bees and butterflies need nectar most (RHS, UC). The RHS lists bees, hoverflies and butterflies among its visitors, and hoverflies are among the beneficial insects in our guide to flowers that attract beneficial insects. Because it likes dry, lean, sunny ground, plant it along a hot path edge or in a gravel strip beside the plot, not in watered beds (our reading). Nebraska suggests it for the hottest, sunniest spots, and UC grows it with ornamental grasses and other low-water perennials. Good neighbors include lavender, yarrow, salvia and coneflowers.

Frequently asked questions

When is the best time to plant sedum?

In spring after frost and before summer heat (Almanac). The RHS also plants in early fall while the soil is still warm.

Can I plant sedum in the fall?

Yes, in early fall while the soil is warm (RHS). Keep new plants watered for the rest of the season.

When should I divide sedum?

In early spring as new growth appears. Keep several shoots and some roots on each piece and replant right away (Iowa State).

Why is my sedum flopping over?

Too much water, fertilizer or shade (Nebraska, UC). Cut stems back by half in late May next year for sturdier plants (RHS).

How do I propagate sedum?

By division in spring or stem cuttings in early summer (RHS, NC State). NC State says it can even regrow from a single leaf.

Should I cut back sedum in the fall?

You can, but the RHS and UC leave the dried flower heads for winter interest and cut the old stems in spring as new shoots appear.