Repotting guide

When & how to repot Silver Tansy (Tanacetum niveum)

Also called Silver Tansy, Niveum Tansy, Snow Tansy.

More about silver tansy

About Silver Tansy

Tanacetum niveum · also called Silver Tansy, Niveum Tansy · flowering

Silver Tansy is a graceful perennial from Turkey and the eastern Mediterranean, forming spreading mounds of intensely silver-white, finely cut aromatic foliage smothered in late spring with masses of small white daisy flowers with yellow centres. Its striking silver foliage provides year-round textural contrast and is highly deer-resistant. It thrives in hot, dry, well-drained positions.

Mature size: Height 30–60 cm (12–24 in) in flower; spread 45–75 cm (18–30 in)

Watch for — Flopping / open habit: Over-rich soil or too much shade causes stems to spread excessively and flop. Cut back hard after flowering to encourage a compact mound; reduce or eliminate feeding and ensure full sun.

How to tell silver tansy needs repotting

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

Thick roots out of the drainage holes, or circling the surface and lifting the plant.
The pot dries out unusually fast and silver tansy wilts between waterings it used to shrug off.
The plant is visibly top-heavy and tips over easily.
Stalled growth and small new leaves over a full season — though with a big specimen, top-dressing is often the better first response before a full repot.

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 silver tansy

Every 2–3 years; top-dress in the in-between years. Silver Tansy's growth habit — spreading, mat- or mound-forming perennial; woody at base with a spreading crown of silver ferny foliage — sets the pace. Silver Tansy is a graceful perennial from Turkey and the eastern Mediterranean, forming spreading mounds of intensely silver-white, finely cut aromatic foliage smothered in late spring with masses of small white daisy flowers with yellow centres. Its striking silver foliage provides year-round textural contrast and is highly deer-resistant. It thrives in hot, dry, well-drained positions.

What size pot to step silver tansy up to

Move up exactly one pot size. A heavy silver tansy dropped into a vastly bigger pot sits in a reservoir of wet soil its roots cannot reach, which rots them and destabilises the plant. In the years between repots, lift off and replace the top 3–5 cm of soil (top-dressing) instead — it refreshes nutrients without the shock of a full repot.

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 silver tansy

Early spring, just as new growth restarts, is the ideal window for silver tansy. The plant is moving into its strongest growth phase and re-roots into fresh soil quickly. Avoid repotting in winter dormancy or, for flowering plants, while it is in bud or bloom — recovery is slowest then and you risk dropping the flowers.

Step-by-step: repotting silver tansy

Consider top-dressing first. If silver tansy is not badly root-bound, scrape off and replace the top 3–5 cm of soil instead — far less shock for a big plant that hates moving.
Get help and one size up. For a full repot, choose a pot just one size larger. A heavy plant needs two people and a stable, free-draining pot.
Ease it out on its side. Lay the plant down, slide the pot off, and gently loosen the outer roots. Do not bare-root a mature specimen.
Repot at the same depth. Add fresh poor to average, sharply drained sandy, gravelly, or rocky soil beneath and around the rootball, keeping the original soil line. Firm it so the trunk is stable and upright.
Water and leave it put. Water thoroughly, then leave silver tansy in the same spot and light — moving and repotting at once is what makes it drop leaves.

Aftercare

Leave silver tansy in exactly the same spot and light it was in before — moving and repotting at the same time is what makes a big specimen drop leaves. Water it in well, then let the top of the soil dry before watering again so the larger volume of fresh soil does not stay sodden. Do not fertilise for about 4 weeks — fresh mix already carries nutrients and feeding freshly disturbed roots scorches them.

The right soil mix for silver tansy

Silver Tansy wants poor to average, sharply drained sandy, gravelly, or rocky soil. Prefers neutral to alkaline pH (6.5–8.0). Thrives in lean soils where many plants struggle — rich, moist conditions encourage lush growth that is prone to flopping and disease. Ideal for gravel gardens, dry slopes, and wall tops. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting silver tansy — frequently asked questions

How often should you repot silver tansy?

Every 2–3 years; top-dress in the in-between years for silver tansy. Fully repot silver tansy only every 2–3 years; in the in-between years just top-dress the top 3–5 cm of soil. Step up one pot size in spring with poor to average, sharply drained sandy, gravelly, or rocky soil. It is heavy and hates being moved, and a vastly oversized pot holds water against the roots and rots them.

What size pot does silver tansy need?

When is the best time of year to repot silver tansy?

Should you top-dress or fully repot silver tansy?

For a big, heavy silver tansy, top-dressing — replacing the top 3–5 cm of soil — is the gentler option most years, with a full repot only every 2–3 years. A mature specimen sulks and drops leaves when fully repotted, so do it as rarely as the roots allow.

Should you fertilise silver tansy after repotting?

Not immediately. Wait about 4 weeks after repotting silver tansy. Fresh mix already contains nutrients, and feeding freshly cut or disturbed roots burns them. Resume your normal feeding routine once you see new growth.