Lithodora (purple gromwell) Glandora diffusa
Lithodora (purple gromwell) (Glandora diffusa) is an evergreen perennial shrub in the Boraginaceae family, native to Heaths and pine woods of south-western Europe (Spain, Portugal, south-west France). It grows 15–30 cm (6–12 in) tall and 50–80 cm (20–31 in) wide, wants full sun and moderate water, and is hardy to about -15 °C (5 °F). Space plants about 45 cm (18 in) apart.
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Lithodora (purple gromwell) at a glance
| Type | Perennial shrub, evergreen |
|---|---|
| Family | Boraginaceae |
| Mature height | 15–30 cm (6–12 in) |
| Mature spread | 50–80 cm (20–31 in) |
| Spacing | 45 cm (18 in) centre to centre |
| Sun | Full sun, at least 5 h of direct sun a day |
| Water | Moderate; drought tolerance low, waterlogging tolerance none |
| Soil pH | 4.5–6.5 |
| Cold hardiness | About -15 °C (5 °F) once established (roughly USDA zone 7) |
| Heat stress | Likely above about 30 °C (86 °F) |
| Flowering | from about May for 6–10 weeks (northern hemisphere; later in cold climates, earlier in warm ones) |
| Wind tolerance | Low |
| Pollinator value | High |
| Edible | Not grown as food |
| Native to | Heaths and pine woods of south-western Europe (Spain, Portugal, south-west France) |
| Common in gardens of | 🇪🇸 Spain, 🇵🇹 Portugal, 🇫🇷 France, 🇬🇧 United Kingdom, 🇮🇪 Ireland, 🇺🇸 United States |
Is Lithodora (purple gromwell) toxic?
- People: not known to be toxic
- Cats: not known to be toxic
- Dogs: not known to be toxic
Not known to be poisonous.
If a child or pet may have eaten part of a plant, call a poison centre or vet straight away.
Companion planting: what to grow with Lithodora (purple gromwell)
No well-documented helpful pairing. Group it with plants that like full sun and moderate water.
Questions about Lithodora (purple gromwell)
- How far apart should I plant Lithodora (purple gromwell)?
- About 45 cm (18 in) apart, centre to centre. A mature plant spreads 50–80 cm (20–31 in).
- Does Lithodora (purple gromwell) need full sun?
- Full sun: at least 5 hours of direct sun a day.
- How much water does Lithodora (purple gromwell) need?
- Moderate water. Drought tolerance is low and waterlogging tolerance none.
- How cold-hardy is Lithodora (purple gromwell)?
- It tolerates about -15 °C (5 °F) once established, roughly USDA zone 7.
- When does Lithodora (purple gromwell) flower?
- From about May for 6–10 weeks (northern hemisphere; later in cold climates, earlier in warm ones).
- Is Lithodora (purple gromwell) poisonous to cats and dogs?
- For cats it is not known to be toxic; for dogs not known to be toxic; for people not known to be toxic. Not known to be poisonous.
- What grows well with Lithodora (purple gromwell)?
- There is no well-documented companion pairing for Lithodora (purple gromwell). Group it with plants that like the same sun (full sun) and water (moderate).
Sources and evidence
Evidence grade A (A: strong evidence).
- Plants of the World Online (taxonomy, native range), Royal Botanic Gardens, Kew
- RHS Find a Plant (plant profiles and growing guides), Royal Horticultural Society
Notes and assumptions
- A rock-garden plant: give it gritty, very free-draining soil, full light and a collar of gravel around the neck; winter wet kills it far more often than cold.
- A spreading evergreen mat of dark, hairy leaves covered in late spring with intense gentian-blue star flowers (‘Heavenly Blue’, ‘Grace Ward’). Needs lime-free soil. Long sold as Lithodora diffusa; now placed in Glandora.
Reference values for planning, not horticultural, veterinary or medical advice. Varieties, soils and local climates differ: check with a local nursery or extension service.
Related plants
- Borage Borago officinalis
- Comfrey Symphytum officinale
- Woodland forget-me-not Myosotis sylvatica
- Lungwort (pulmonaria) Pulmonaria officinalis
- Heliotrope Heliotropium arborescens
- Tree echium (giant viper's bugloss) Echium pininana
- Virginia bluebells Mertensia virginica
- Pride of Madeira Echium candicans