Repotting guide

When & how to repot Grosso lavandin (Lavandula x intermedia 'Grosso')

Also called Grosso lavandin, Fat Spike lavender, Grosso lavender.

More about grosso lavandin

About Grosso lavandin

Lavandula x intermedia 'Grosso' · also called Grosso lavandin, Fat Spike lavender · herb

The world's most commercially grown lavender cultivar, 'Grosso' dominates the essential-oil industry of Provence with its exceptionally large, fat, deep-violet flower spikes and very high linalool oil yield. A vigorous, long-lived lavandin with a strongly sweet-camphor fragrance, it makes a magnificent garden plant for large borders, lavender fields, and dried-flower harvest.

Mature size: 60–90 cm tall (24–36 in), spreading up to 120 cm (48 in)

Watch for — Root rot: The single greatest killer of 'Grosso' outside its native range. Overwatering or poor drainage causes rapid collapse. Site on a slope or raised mound, plant through gravel mulch, and never irrigate established plants unless in severe drought.

How to tell grosso lavandin needs repotting

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

A dense root mass with little soil visible when you ease grosso lavandin 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 grosso lavandin

Every 2–4 years — it is in no hurry. Grosso lavandin's growth habit — large, dense, rounded woody-based evergreen subshrub; sterile; long stems topped with distinctively fat, branched flower spikes — sets the pace. The world's most commercially grown lavender cultivar, 'Grosso' dominates the essential-oil industry of Provence with its exceptionally large, fat, deep-violet flower spikes and very high linalool oil yield. A vigorous, long-lived lavandin with a strongly sweet-camphor fragrance, it makes a magnificent garden plant for large borders, lavender fields, and dried-flower harvest.

What size pot to step grosso lavandin up to

Step up just one pot size, and only when the roots are genuinely packed. Because grosso lavandin 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 grosso lavandin

Early spring, just as new growth restarts, is the ideal window for grosso lavandin. 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 grosso lavandin

Time it for spring. Repot grosso lavandin 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 grosso lavandin out and gently loosen any roots circling the bottom of the rootball.
Repot at the same depth. Put a layer of fresh very well-drained, infertile, calcareous or sandy loam 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 grosso lavandin 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 grosso lavandin

Grosso lavandin wants very well-drained, infertile, calcareous or sandy loam. Performs best on calcium-rich, stony, or sandy soils with excellent drainage. pH 6.5–8.5. Traditional Provençal cultivation is on rocky limestone plateaus — replicate this with grit-amended, raised planting. Rich or waterlogged soils reduce oil quality and plant longevity. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting grosso lavandin — frequently asked questions

How often should you repot grosso lavandin?

Every 2–4 years — it is in no hurry for grosso lavandin. Repot grosso lavandin 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 very well-drained, infertile, calcareous or sandy loam. 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 grosso lavandin need?

When is the best time of year to repot grosso lavandin?

Can you put grosso lavandin straight into a much bigger pot?

No. Even a fast-growing grosso lavandin 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 grosso lavandin after repotting?

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