Fertilising guide
How to fertilise Spike lavender (Lavandula latifolia)— schedule & NPK
Also called Spike lavender, Broad-leaved lavender, Portuguese lavender.
More about spike lavender
About Spike lavender
Lavandula latifolia · also called Spike lavender, Broad-leaved lavender · herb
Spike lavender is a robust, camphor-scented Mediterranean herb valued for its essential oil and tall flower spikes. It thrives in full sun with sharply drained, poor-to-average soil and extreme drought tolerance once established. Slightly coarser than English lavender, it blooms mid to late summer and tolerates hotter, more humid summers than its relatives.
Growth habit: Upright, woody-based evergreen subshrub forming a dense mound of grey-green, broad, linear leaves with tall erect flower spikes rising above the foliage
What fertiliser spike lavender actually wants — and why
Spike 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 spike 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 spike 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 spike lavender:
Apply a low-nitrogen, high-potassium fertiliser (tomato feed) once in early spring, if at all. Rich feeding produces lush, soft growth prone to disease and reduces flowering and essential oil concentration. Established plants in well-chosen sites need no feeding. 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 spike 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 spike lavender
Half strength is a sensible default for spike 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 spike lavender first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the spike lavender watering schedule.
Signs you are over-feeding spike lavender
Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for spike 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 spike 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 spike lavender care brief covers soil, humidity and the common problems for this species.
Flushing and leaching the salts
Pot-grown spike 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 spike 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 spike lavender — frequently asked questions
What fertiliser does spike 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. Spike 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 spike lavender?
Apply a low-nitrogen, high-potassium fertiliser (tomato feed) once in early spring, if at all. Rich feeding produces lush, soft growth prone to disease and reduces flowering and essential oil concentration. Established plants in well-chosen sites need no feeding. Apply a low-nitrogen, high-potassium fertiliser (tomato feed) once in early spring, if at all. Rich feeding produces lush, soft growth prone to disease and reduces flowering and essential oil concentration. Established plants in well-chosen sites need no feeding. 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 spike lavender?
Half strength is a sensible default for spike lavender — enough to fuel regrowth after cutting, gentle enough that the leaves stay aromatic rather than watery.
What does over-feeding spike 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 spike 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 spike lavender?
Pot-grown spike 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
- Spike lavender care — the full brief (light, soil, humidity, problems, pet safety)
- How often to water spike 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 curly parsley
- How to fertilise garlic chives
- How to fertilise lavandin
- All 6887 fertilising guides in the Growli library