How to Grow Costmary UK | Regional Planting Calendar

Regional Planting Calendar

Quick Facts

Factor	Value
Soil pH	5.5 - 7.5
Sunlight	2-6 hours direct sun
Soil texture	Clay, loam or sand (RHS; NC State Extension)
Drainage	Good drainage preferred; tolerates moist to occasionally dry conditions (NC State Extension)
Lifecycle	Woody-based, rhizomatous herbaceous perennial (RHS; NC State Extension)
Edible parts	leaves

At a Glance

Soil & Growing Conditions

Water: Tolerates moist to occasionally dry soil (NC State Extension)

Soil pH range

5.5 7.5

Span reflects genuine variation between the cited authorities, not a single agreed figure.

Growth Stages

Stage	BBCH	Notes
Establishment	0	Propagate by division or by semi-hardwood/root/stem cuttings rather than seed, which germinates poorly (RHS; NC State Extension). Space new plants 3-6ft apart to allow for its spreading, rhizomatous habit (NC State Extension).
Vegetative growth	3	Grows readily in full sun or partial shade in any reasonably well-drained soil; shade produces mostly leaves with little flowering. Growth is rapid and can become aggressive if not managed (NC State Extension). Takes 2-5 years to reach full maturity (RHS).
Flowering	6	Small, yellow, daisy-like button flowers appear in loose corymbs from September to October (RHS; NC State Extension).
Cutting back and harvest	8	Fresh leaves can be picked for culinary use throughout the growing season. Cut the whole plant back after flowering to prevent legginess and encourage fresh new foliage (RHS; NC State Extension).

Harvest & Storage

When to pick: Fresh leaves can be picked through the growing season to flavour salads, soups and meats, or to make tea (NC State Extension). Cut back after flowering to keep the plant tidy and encourage fresh foliage (RHS).

Diseases

Pests

Costmary Photo Gallery

Costmary in flower

Costmary's small, daisy-like flowers, with yellow disc florets and short white rays, matching the classic description of the species.

Labelled costmary specimen

A young costmary plant with its identification label, confirming the species.

Costmary, 'bible leaf'

An information card for costmary (Marienblatt), noting its historical use pressed into bibles as a fragrant bookmark.

Costmary in bloom

Costmary's small yellow button-like flower clusters on tall stems.

Costmary foliage

The oblong, grey-green, balsam-scented leaves of costmary.

Costmary growing in a garden bed

Costmary grown as a low, spreading herb bed.

A costmary plant

A mature costmary plant showing its typical growth habit.

Costmary leaf detail

Detail of costmary's characteristic oblong leaves, used fresh to flavour salads, soups and tea.

References

1. NC State Extension Gardener Plant Toolbox - Tanacetum balsamita (Alecost, Balsam Weed, Bible Leaf, Bible Plant, Chrysanthemum, Costmary, Mint Geranium, Sweet Mary)

   Rhizomatous herbaceous perennial. USDA zones 5a-7b. Full sun (6+ hrs) or partial shade (2-6 hrs) -- shade produces mostly leaves without flowering. Soil clay, loam or sand; pH acidic to neutral (below 8.0); good drainage preferred, tolerates moist to occasionally dry. Shallow root system. Height 3-6ft, width 1ft4in-3ft6in; space plants 3-6ft apart. Rapid growth, can become aggressive. Regular clipping prevents legginess. Propagate by division, root cuttings, stem cuttings, or seed (seed has difficulty germinating). Blooms September-October, small yellow button-like flowers in corymbs. Leaves 4-8in, silvery-green, oval to elliptic, minty-balsam scent. Fresh leaves used to flavour salads, soups, meats and ales, and to make tea; historically used as a diuretic, laxative and antipyretic. No serious pests or diseases reported; occasionally susceptible to Southern Blight of Herbaceous Ornamentals. Native to Southern Europe and Western Asia.

2. Royal Horticultural Society - Tanacetum balsamita (costmary)

   Woody-based herbaceous perennial with deciduous, oblong, grey-green, balsam-scented leaves and small daisy-like yellow/white flowers late summer to early autumn. Grow in any light, well-drained soil (loam or sand, acid/alkaline/neutral) in full sun or partial shade; south/west/east-facing, exposed or sheltered. Hardiness H7 (below -20C). Height 0.5-1m, spread 0.1-0.5m. Time to maturity 2-5 years. Cut back after flowering. Propagate by seed or semi-hardwood cuttings in summer. Susceptible to aphids, leaf and bud eelworms, and leaf-mining flies; generally disease-free. Contact may irritate the skin -- wear gloves and other protective equipment. Native to South Europe and Southwest Asia. Family Asteraceae.

2 independent sources are cited for this crop. Where they disagree - soil pH is the clearest case - every figure is preserved rather than averaged into false precision.