Repotting guide

When & how to repot Cat Thyme (Teucrium marum)

Also called Cat Thyme, Kitty Crack, Mediterranean Germander, Cat Crack.

More about cat thyme

About Cat Thyme

Teucrium marum · also called Cat Thyme, Kitty Crack · herb

Teucrium marum is a compact, evergreen subshrub native to the western Mediterranean, particularly Sardinia and the Balearic Islands. It produces grey-green, downy, aromatic foliage and small pink flowers on slender spikes in late summer and autumn. Full sun and sharply drained, alkaline soil are essential — winter wet is more damaging than frost. The plant is mildly toxic if ingested; the RHS advises wearing gloves when handling, though it is famous for attracting cats with a catnip-like effect.

Mature size: Approximately 30–40 cm tall and 30–40 cm wide.

Watch for — Root rot from winter wet: The most frequent killer; ensure the planting site has near-perfect drainage and consider a grit mulch around the collar to divert standing water.

How to tell cat thyme needs repotting

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

A dense root mass with little soil visible when you ease cat thyme out of its pot — check once a year rather than assuming.
Roots emerging from the drainage holes (slow on this plant, so this is a strong signal).
The plant has become top-heavy and tips its pot over.
Genuinely stalled growth across a full season despite adequate light — not just the naturally slow pace this plant always has.

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 cat thyme

Every 2–4 years — it is in no hurry. Cat Thyme's growth habit — compact, bushy evergreen subshrub with a mounded form. — sets the pace. Teucrium marum is a compact, evergreen subshrub native to the western Mediterranean, particularly Sardinia and the Balearic Islands. It produces grey-green, downy, aromatic foliage and small pink flowers on slender spikes in late summer and autumn. Full sun and sharply drained, alkaline soil are essential — winter wet is more damaging than frost. The plant is mildly toxic if ingested; the RHS advises wearing gloves when handling, though it is famous for attracting cats with a catnip-like effect.

What size pot to step cat thyme up to

Step up just one pot size, and only when the roots are genuinely packed. Because cat thyme grows so slowly, a big pot of damp soil will simply sit wet for months around a small root system and invite rot. A snug pot suits this plant; resist the urge to "give it room to grow" — it will not use it.

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 cat thyme

Early spring, just as new growth restarts, is the ideal window for cat thyme. 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 cat thyme

Time it for spring. Repot cat thyme in early spring as growth restarts so it re-roots quickly into the fresh soil.
Choose one size up. Pick a pot about 2–3 cm wider with drainage holes. One step only — a much bigger pot stays soggy and rots roots.
Ease the plant out. Water lightly the day before, then tip cat thyme out and gently loosen any roots circling the bottom of the rootball.
Repot at the same depth. Put a layer of fresh well-drained chalk, loam, or sand; neutral to alkaline ph in the new pot, set the plant so its soil line is unchanged, and backfill, firming lightly.
Water and pause feeding. Water once to settle the soil. Hold off fertiliser for about a month — fresh mix already has nutrients and feeding now burns new roots.

Aftercare

Because the new soil holds more water than the old crammed rootball did, ease right back on watering — let the top of the soil dry before you water cat thyme again, or you will rot the roots in the very pot you just moved it to. Keep it out of harsh direct sun for a fortnight. Do not fertilise for about 4 weeks — fresh mix already carries nutrients and feeding freshly disturbed roots scorches them.

The right soil mix for cat thyme

Cat Thyme wants well-drained chalk, loam, or sand; neutral to alkaline ph. Good drainage is non-negotiable; add grit liberally when planting in heavier soils and avoid any site that holds moisture in winter. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting cat thyme — frequently asked questions

How often should you repot cat thyme?

Every 2–4 years — it is in no hurry for cat thyme. Repot cat thyme only every 2–4 years — it builds roots slowly and a yearly repot is wasted effort. Move up just one pot size in spring with fresh well-drained chalk, loam, or sand; neutral to alkaline ph. The main error is repotting too often and into too large a pot, which leaves cold wet soil around the roots.

What size pot does cat thyme need?

When is the best time of year to repot cat thyme?

Can you put cat thyme straight into a much bigger pot?

No. Even a fast-growing cat thyme should only go up one pot size at a time. A vastly oversized pot holds a reservoir of wet soil the roots cannot reach, which stays cold and soggy and rots the roots — the opposite of what you wanted.

Should you fertilise cat thyme after repotting?

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