Fertilising guide
How to fertilise Grosso Lavender (Lavandula × intermedia 'Grosso')— schedule & NPK
Also called Lavandin.
More about grosso lavender
About Grosso Lavender
Lavandula × intermedia 'Grosso' · also called Lavandin · herb
'Grosso' is the world's most widely grown lavandin, a sterile English-x-Portuguese hybrid bred for high oil yield and long, fragrant violet wands. It is larger, more vigorous, and more disease-resistant than English lavender, blooming in mid-to-late summer. It demands full sun and sharp drainage and dislikes humidity and rich, wet soil.
Growth habit: Large, vigorous, rounded evergreen subshrub with silvery foliage and very long flower stalks held well above the mound; woody at the base over time.
Watch for — Flopping after rain or feeding: Long, heavy flower stalks bend under wet weather or rich soil. Keep it lean and unfed and shear flower stems promptly.
What fertiliser grosso lavender actually wants — and why
Grosso Lavender is a soft, fast leafy herb that you harvest hard — a modest balanced feed keeps tender growth coming without tipping it into bland or bolting.
A balanced general feed (even N-P-K) at modest strength — enough nitrogen to keep replacing the leaves you pick, but not so much that flavour thins or it bolts to seed.
For the language behind the three numbers on the bottle — what nitrogen, phosphorus and potassium each do — see the NPK ratio explained entry. The short version for grosso lavender: match the feed to the job the plant is doing right now, not to a generic “plant food” on the shelf.
How often to feed grosso lavender, and which months
Feeding only earns its keep while the plant is in active growth and can use the nutrients — pour feed into a dormant or low-light plant and it simply builds up as root-burning salt. For grosso lavender:
Minimal feeding. One light low-nitrogen application in spring is sufficient. Rich feeding produces soft growth, fewer flowers, and weaker scent. In practice: a balanced liquid feed every few weeks through the main growing and harvesting season (spring through early autumn), more often the harder you are picking it.
The dormant-season rule matters more than the exact interval: skip feeding entirely when grosso lavender is resting. For the wider context on indoor feeding rhythms across the seasons, the houseplant fertiliser schedule walks through the year month by month.
What strength to mix for grosso lavender
Half strength is a sensible default for grosso lavender — enough to fuel regrowth after cutting, gentle enough that the leaves stay aromatic rather than watery.
Feeding always goes onto already-damp soil, never dry roots — water grosso lavender first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the grosso lavender watering schedule.
Signs you are over-feeding grosso lavender
Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for grosso lavender:
- Fast, soft, pale growth with diluted, less aromatic flavour.
- Early bolting (running to flower) and a bitter edge.
- Salt crust and scorched tips on container plants.
Signs you are under-feeding grosso lavender
- Pale, slow regrowth after cutting and small leaves.
- A tired, stalled plant that cannot keep up with harvesting.
- Yellowing older leaves in a long-spent pot.
If the symptoms point at watering, light or roots rather than nutrition, the full grosso lavender care brief covers soil, humidity and the common problems for this species.
Flushing and leaching the salts
Pot-grown grosso lavender builds up feed salts quickly — water until it drains each time and flush the pot with plain water every few weeks, especially on a sunny windowsill.
Organic vs synthetic feeds for grosso lavender
Organic options
A diluted seaweed feed or worm-casting tea keeps soft growth coming without overdoing it. UK: dilute seaweed or Westland; US: Espoma Garden-tone or Neptune's Harvest. Gentle, hard to overdo, flavour-friendly.
Synthetic / liquid feeds
A balanced liquid feed at half strength through harvesting — UK: Phostrogen, Baby Bio or Westland; US: Miracle-Gro all-purpose at half strength. Fast regrowth; just do not overdo the nitrogen.
Brand names are examples, not endorsements, and UK and US ranges differ — check the label’s own NPK and dilution rate, since formulations change.
Fertilising grosso lavender — frequently asked questions
What fertiliser does grosso lavender need?
A balanced general feed (even N-P-K) at modest strength — enough nitrogen to keep replacing the leaves you pick, but not so much that flavour thins or it bolts to seed. Grosso Lavender is a soft, fast leafy herb that you harvest hard — a modest balanced feed keeps tender growth coming without tipping it into bland or bolting.
How often should I feed grosso lavender?
Minimal feeding. One light low-nitrogen application in spring is sufficient. Rich feeding produces soft growth, fewer flowers, and weaker scent. Minimal feeding. One light low-nitrogen application in spring is sufficient. Rich feeding produces soft growth, fewer flowers, and weaker scent. In practice: a balanced liquid feed every few weeks through the main growing and harvesting season (spring through early autumn), more often the harder you are picking it.
What strength of feed for grosso lavender?
Half strength is a sensible default for grosso lavender — enough to fuel regrowth after cutting, gentle enough that the leaves stay aromatic rather than watery.
What does over-feeding grosso lavender look like?
Fast, soft, pale growth with diluted, less aromatic flavour. Early bolting (running to flower) and a bitter edge. Salt crust and scorched tips on container plants. Over-feeding grosso lavender with strong nitrogen is the usual mistake — it grows fast and lush but the leaves turn bland and it bolts to flower sooner, ending the useful harvest early.
Should I flush the soil of grosso lavender?
Pot-grown grosso lavender builds up feed salts quickly — water until it drains each time and flush the pot with plain water every few weeks, especially on a sunny windowsill.
Keep reading
- Grosso Lavender care — the full brief (light, soil, humidity, problems, pet safety)
- How often to water grosso lavender — the watering schedule
- The houseplant fertiliser schedule — feeding through the year
- NPK ratio explained — what the three numbers on the bottle mean
- How to fertilise basil
- How to fertilise herb garden
- How to fertilise mint
- All 1284 fertilising guides in the Growli library