Fertilising guide
How to fertilise White Horehound (Marrubium vulgare)— schedule & NPK
Also called White Horehound, Common Horehound, Horehound.
More about white horehound
About White Horehound
Marrubium vulgare · also called White Horehound, Common Horehound · herb
White Horehound is a bitter, woolly-leaved perennial herb in the Lamiaceae family, native to the Mediterranean and central Asia and naturalized widely across North America and Australia. Its wrinkled, grey-green leaves contain marrubiin, used in traditional cough remedies and candies. Hardy, drought-tolerant, and pest-resistant, it excels in sunny, poor, well-drained soils.
Growth habit: Clump-forming, spreading herbaceous perennial with woolly, grey-green foliage
What fertiliser white horehound actually wants — and why
White Horehound 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 white horehound: 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 white horehound, 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 white horehound:
Little to no fertiliser required. In very nutrient-poor soil, a single application of a balanced granular feed in early spring is sufficient. High-nitrogen feeding produces rank, floppy stems and reduces the bitterness valued in herbal preparations. 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 white horehound 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 white horehound
Half strength is a sensible default for white horehound — 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 white horehound first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the white horehound watering schedule.
Signs you are over-feeding white horehound
Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for white horehound:
- 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 white horehound
- 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 white horehound care brief covers soil, humidity and the common problems for this species.
Flushing and leaching the salts
Pot-grown white horehound 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 white horehound
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 white horehound — frequently asked questions
What fertiliser does white horehound 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. White Horehound 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 white horehound?
Little to no fertiliser required. In very nutrient-poor soil, a single application of a balanced granular feed in early spring is sufficient. High-nitrogen feeding produces rank, floppy stems and reduces the bitterness valued in herbal preparations. Little to no fertiliser required. In very nutrient-poor soil, a single application of a balanced granular feed in early spring is sufficient. High-nitrogen feeding produces rank, floppy stems and reduces the bitterness valued in herbal preparations. 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 white horehound?
Half strength is a sensible default for white horehound — enough to fuel regrowth after cutting, gentle enough that the leaves stay aromatic rather than watery.
What does over-feeding white horehound 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 white horehound 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 white horehound?
Pot-grown white horehound 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
- White Horehound care — the full brief (light, soil, humidity, problems, pet safety)
- How often to water white horehound — 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 coconut thyme
- How to fertilise banana mint
- How to fertilise grapefruit mint
- All 8452 fertilising guides in the Growli library