Repotting guide

When & how to repot Woolly yarrow (Achillea tomentosa)

Also called Woolly yarrow, Yellow wooly yarrow.

More about woolly yarrow

About Woolly yarrow

Achillea tomentosa · also called Woolly yarrow, Yellow wooly yarrow · flowering

A low-growing, mat-forming yarrow prized for its dense, soft grey-green woolly foliage and cheerful yellow flower heads held above the carpet on short stems. Superb for the front of sunny borders, rock gardens, dry slopes, and paving crevices. Extremely drought-tolerant and heat-resistant once established, it withstands light foot traffic and suppresses weeds effectively.

Mature size: 10–20 cm tall in flower (4–8 in), spreading 30–45 cm (12–18 in)

Watch for — Loss of compact habit: Mats can become open and die out at the centre after several years. Divide clumps every 3–4 years in spring, replanting vigorous outer sections into freshly prepared ground.

How to tell woolly yarrow needs repotting

Repotting on a calendar is less reliable than reading the plant. For woolly yarrow, watch for these signs:

Roots growing out of the drainage holes, or the rootball lifting the plant proud of the rim.
Soil that has shrunk away from the pot sides and no longer holds water.
The pot is unstable because the plant has grown top-heavy.
Old, compacted, broken-down mix that stays wet too long — for a succulent that is a rot risk, so refresh it even if the pot size is fine.

For the underlying biology of a pot-bound root system and why it stalls a plant, see our guide to spotting and fixing a root-bound plant.

How often to repot woolly yarrow

Every 2–3 years, into bone-dry mix. Woolly yarrow's growth habit — low-growing, mat-forming herbaceous perennial; spreading groundcover with woolly silvery-green leaf rosettes — sets the pace. A low-growing, mat-forming yarrow prized for its dense, soft grey-green woolly foliage and cheerful yellow flower heads held above the carpet on short stems. Superb for the front of sunny borders, rock gardens, dry slopes, and paving crevices. Extremely drought-tolerant and heat-resistant once established, it withstands light foot traffic and suppresses weeds effectively.

What size pot to step woolly yarrow up to

Use a pot only one size up — or even the same pot with fresh gritty mix if the roots have room. Woolly yarrow stores water and rots in a large pot of slow-drying soil. A tight terracotta pot that dries fast is far safer than a generous plastic one. Never up-pot a succulent by several sizes.

Not sure of the exact diameter? Our pot size calculator takes the current pot and root spread and tells you the right next size — it deliberately recommends a single step up, never a big jump.

The best time of year to repot woolly yarrow

Spring or summer, while woolly yarrow is in active growth and warm, is best — roots recover fastest then, and the plant is not sitting in cool damp soil. Avoid repotting a succulent in winter dormancy.

Step-by-step: repotting woolly yarrow

Repot dry. Do not water woolly yarrow for several days first. Working with dry roots and dry mix dramatically lowers the rot risk for a succulent.
Pick a snug, fast-draining pot. Choose terracotta one size up at most, with a drainage hole. Have gritty very well-drained, lean, sandy or gritty soil ready.
Tip it out and clean the roots. Slide the plant out, crumble off the old soil, and trim any black, mushy or dead roots with clean snips.
Pot into dry mix. Set woolly yarrow at its original depth in dry gritty mix, firming gently. Do not bury the stem deeper than it was.
Wait a week before watering. Leave it completely dry and out of harsh sun for about 7 days so any damaged roots callus. Only then water lightly.

Aftercare

Keep woolly yarrow completely dry and out of fierce sun for about a week so any nicked roots callus before they meet moisture; watering a freshly repotted succulent is the classic way to rot it. Then resume the normal lean, dry rhythm. Do not fertilise for about 3 weeks — fresh mix already carries nutrients and feeding freshly disturbed roots scorches them.

The right soil mix for woolly yarrow

Woolly yarrow wants very well-drained, lean, sandy or gritty soil. Thrives in poor, sharply drained soils including sand, gravel, and scree. Absolutely intolerant of heavy clay or wet winter soils. pH 6.0–8.0; tolerates alkaline ground well. Adding grit when planting in heavier soils is strongly recommended. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting woolly yarrow — frequently asked questions

How often should you repot woolly yarrow?

Every 2–3 years, into bone-dry mix for woolly yarrow. Repot woolly yarrow every 2–3 years into a snug pot of very well-drained, lean, sandy or gritty soil, ideally in spring or summer. Let it sit in dry soil and do not water for about a week afterwards so any nicked roots can callus. Over-potting and watering straight away is what rots succulents.

What size pot does woolly yarrow need?

When is the best time of year to repot woolly yarrow?

Should you water woolly yarrow after repotting?

No — not straight away. Repot woolly yarrow into dry mix and wait about a week before the first watering so any damaged roots callus over. Watering a freshly repotted succulent is the single most common way to rot one.

Should you fertilise woolly yarrow after repotting?

Not immediately. Wait about 3 weeks after repotting woolly yarrow. Fresh mix already contains nutrients, and feeding freshly cut or disturbed roots burns them. Resume your normal feeding routine once you see new growth.