Repotting guide

When & how to repot Green Cotton Lavender (Santolina rosmarinifolia)

Also called Green cotton lavender, Green santolina, Holy flax, Rosemary-leaved lavender cotton.

More about green cotton lavender

About Green Cotton Lavender

Santolina rosmarinifolia · also called Green cotton lavender, Green santolina · herb

Santolina rosmarinifolia is a compact, evergreen sub-shrub native to the Iberian Peninsula and northwestern Africa, thriving in hot, sunny, and sharply drained Mediterranean conditions. Its fine, needle-like, bright green aromatic foliage is distinctive within the genus, and it bears clusters of bright yellow button flowers in summer. The single most important care rule is excellent drainage: this plant will rot quickly in wet or waterlogged soil, especially over winter. Santolina is not listed on the ASPCA toxic or non-toxic plant database; as its aromatic oils can cause mild GI upset and contact dermatitis in sensitive individuals, treat it as mildly toxic around pets.

Mature size: 0.5–1 m tall and 0.5–1 m wide after 5–10 years.

Watch for — Root and crown rot: The most frequent killer: caused by waterlogged or poorly drained soil, especially in winter. Ensure the planting site has fast drainage and avoid mulching directly against the woody base.

How to tell green cotton lavender needs repotting

Repotting on a calendar is less reliable than reading the plant. For green cotton lavender, watch for these signs:

A dense root mass with little soil visible when you ease green cotton lavender 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 green cotton lavender

Every 2–4 years — it is in no hurry. Green Cotton Lavender's growth habit — mound-forming, bushy evergreen sub-shrub with an upright to spreading habit. — sets the pace. Santolina rosmarinifolia is a compact, evergreen sub-shrub native to the Iberian Peninsula and northwestern Africa, thriving in hot, sunny, and sharply drained Mediterranean conditions. Its fine, needle-like, bright green aromatic foliage is distinctive within the genus, and it bears clusters of bright yellow button flowers in summer. The single most important care rule is excellent drainage: this plant will rot quickly in wet or waterlogged soil, especially over winter. Santolina is not listed on the ASPCA toxic or non-toxic plant database; as its aromatic oils can cause mild GI upset and contact dermatitis in sensitive individuals, treat it as mildly toxic around pets.

What size pot to step green cotton lavender up to

Step up just one pot size, and only when the roots are genuinely packed. Because green cotton lavender 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 green cotton lavender

Early spring, just as new growth restarts, is the ideal window for green cotton lavender. 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 green cotton lavender

Time it for spring. Repot green cotton lavender 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 green cotton lavender out and gently loosen any roots circling the bottom of the rootball.
Repot at the same depth. Put a layer of fresh poor to moderately fertile, sharply draining; chalk, loam, or sand 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 green cotton lavender 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 green cotton lavender

Green Cotton Lavender wants poor to moderately fertile, sharply draining; chalk, loam, or sand. Thrives in lean, alkaline to neutral soils; rich or moisture-retentive soils encourage lush growth that is prone to splitting and rot. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting green cotton lavender — frequently asked questions

How often should you repot green cotton lavender?

Every 2–4 years — it is in no hurry for green cotton lavender. Repot green cotton lavender 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 poor to moderately fertile, sharply draining; chalk, loam, or sand. 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 green cotton lavender need?

When is the best time of year to repot green cotton lavender?

Can you put green cotton lavender straight into a much bigger pot?

No. Even a fast-growing green cotton lavender 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 green cotton lavender after repotting?

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