Fertilising guide

How to fertilise Spanish Wood Thyme (Thymus mastichina)— schedule & NPK

Also called Spanish wood thyme, Mastic thyme, Spanish marjoram, Herb mastic.

More about spanish wood thyme

About Spanish Wood Thyme

Thymus mastichina · also called Spanish wood thyme, Mastic thyme · herb

Thymus mastichina is an upright, bushy evergreen subshrub native to the Iberian Peninsula (Spain and Portugal), notable for its unusually strong, camphor-and-eucalyptus scent rather than the classic thyme fragrance of its relatives. It produces rounded clusters of small white flowers in summer on grey-green, softly aromatic stems and is widely used in Spanish cooking as a marjoram substitute. Perfect drainage and full sun are essential — this thyme is unforgiving of wet, airless soil conditions. The ASPCA lists thyme (Thymus) as non-toxic to cats and dogs.

Growth habit: Upright, bushy, rounded evergreen subshrub — taller and more erect than most thymes.

What fertiliser spanish wood thyme actually wants — and why

Spanish Wood Thyme is a lean, aromatic herb — the essential-oil flavour you grow it for is strongest in poor soil, so feeding it actively makes it worse.

Little or nothing. If anything, a very weak balanced feed or a thin compost top-dress — never a rich nitrogen feed, which dilutes the aromatic oils and produces soft, bland, floppy growth.

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 spanish wood thyme: 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 spanish wood thyme, 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 spanish wood thyme:

Fertilise lightly once in early spring with a balanced or low-nitrogen feed; excess nutrients produce soft, aromatic-poor growth and reduce cold hardiness. In practice: a spring compost top-dress at most, and otherwise leave spanish wood thyme unfed — lean, sharp-draining soil is exactly what concentrates its flavour.

The dormant-season rule matters more than the exact interval: skip feeding entirely when spanish wood thyme 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 spanish wood thyme

As weak as it gets for spanish wood thyme, or none at all. The flavour-versus-growth trade-off runs the opposite way to leafy crops: restraint is the technique.

Feeding always goes onto already-damp soil, never dry roots — water spanish wood thyme first if the soil is dry, then apply the diluted feed. The companion question is when to water at all, covered in the spanish wood thyme watering schedule.

Signs you are over-feeding spanish wood thyme

Over-feeding is far more common — and more damaging — than under-feeding for most plants. The classic tells for spanish wood thyme:

Lush, soft, fast growth with noticeably weaker scent and flavour.
Floppy stems, sparse essential oils, and poor cold/wet hardiness.
Salt crust in containers and scorched leaf tips from over-feeding.

Signs you are under-feeding spanish wood thyme

Rare — these herbs thrive on lean soil.
Only on truly exhausted soil: pale, thin, very slow growth.
A short-lived, weak plant in a long-spent container.

If the symptoms point at watering, light or roots rather than nutrition, the full spanish wood thyme care brief covers soil, humidity and the common problems for this species.

Flushing and leaching the salts

Over-feeding is so unlikely with spanish wood thyme that flushing is rarely needed; if a container has had feed, a single plain-water flush and a switch to a leaner, grittier mix resets it.

Organic vs synthetic feeds for spanish wood thyme

Organic options

A thin spring mulch of garden compost or leaf-mould is the most these want. UK: a little garden compost; US: a light Espoma Garden-tone top-dress at most. Lean and gritty beats fed and rich every time.

Synthetic / liquid feeds

Generally none for spanish wood thyme. At absolute most, a very dilute balanced feed once or twice in a container; in the ground, nothing — synthetic feeds work directly against the flavour.

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 spanish wood thyme — frequently asked questions

What fertiliser does spanish wood thyme need?

Little or nothing. If anything, a very weak balanced feed or a thin compost top-dress — never a rich nitrogen feed, which dilutes the aromatic oils and produces soft, bland, floppy growth. Spanish Wood Thyme is a lean, aromatic herb — the essential-oil flavour you grow it for is strongest in poor soil, so feeding it actively makes it worse.

How often should I feed spanish wood thyme?

Fertilise lightly once in early spring with a balanced or low-nitrogen feed; excess nutrients produce soft, aromatic-poor growth and reduce cold hardiness. Fertilise lightly once in early spring with a balanced or low-nitrogen feed; excess nutrients produce soft, aromatic-poor growth and reduce cold hardiness. In practice: a spring compost top-dress at most, and otherwise leave spanish wood thyme unfed — lean, sharp-draining soil is exactly what concentrates its flavour.

What strength of feed for spanish wood thyme?