Repotting guide

When & how to repot Rock Thyme (Thymus comptus)

Also called Rock thyme, Compact thyme.

More about rock thyme

About Rock Thyme

Thymus comptus · also called Rock thyme, Compact thyme · herb

Thymus comptus is a low, mat-forming alpine thyme native to limestone rocks and screes of the western Balkans and southern Alps. It thrives in full sun with sharp drainage and extremely lean, alkaline soil — excess moisture in winter is the single most common killer. Trim lightly after flowering to keep growth compact and prevent woody die-back from the centre. Thyme is listed by the ASPCA as non-toxic to cats, dogs, and horses.

Mature size: 3–5 cm tall, 20–40 cm spread.

Watch for — Root rot in wet soil: The most common cause of failure; roots sitting in waterlogged or clay-heavy soil quickly rot, especially over winter. Ensure perfect drainage and consider raising the bed or adding a deep gravel layer.

How to tell rock thyme needs repotting

Repotting on a calendar is less reliable than reading the plant. For rock thyme, 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 rock thyme

Every 2–3 years, into bone-dry mix. Rock Thyme's growth habit — prostrate, mat-forming sub-shrub spreading outwards from a woody central crown. — sets the pace. Thymus comptus is a low, mat-forming alpine thyme native to limestone rocks and screes of the western Balkans and southern Alps. It thrives in full sun with sharp drainage and extremely lean, alkaline soil — excess moisture in winter is the single most common killer. Trim lightly after flowering to keep growth compact and prevent woody die-back from the centre. Thyme is listed by the ASPCA as non-toxic to cats, dogs, and horses.

What size pot to step rock thyme up to

Use a pot only one size up — or even the same pot with fresh gritty mix if the roots have room. Rock Thyme 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 rock thyme

Spring or summer, while rock thyme 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 rock thyme

Repot dry. Do not water rock thyme 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 sharply drained, lean, gritty or rocky alkaline to neutral 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 rock thyme 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 rock thyme 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 rock thyme

Rock Thyme wants sharply drained, lean, gritty or rocky alkaline to neutral soil. A mix of horticultural grit (50%) and loam or topsoil works well; avoid rich compost, which promotes soft, disease-prone growth. Ideal pH 6.5–8.0. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting rock thyme — frequently asked questions

How often should you repot rock thyme?

Every 2–3 years, into bone-dry mix for rock thyme. Repot rock thyme every 2–3 years into a snug pot of sharply drained, lean, gritty or rocky alkaline to neutral 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 rock thyme need?

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

Should you water rock thyme after repotting?

No — not straight away. Repot rock thyme 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 rock thyme after repotting?

Not immediately. Wait about 3 weeks after repotting rock 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.