Lithodora diffusa [li-tho-do-ra] belongs to the Boraginaceae family of flowering plants and is native to the southwestern regions of Europe including southern Greece, Algeria and Turkey and Northwestern France.
The Greek word lithodora literally translates to “stone gift” referring to the rocky nature of the plant.
Other common names include:
- Lithodora diffusa star
- Lithodora diffusa Grace Ward
- Grace ward
- Grace Ward Lithodora
- Purple Gromwell
Botanical names of the lithodora are:
- Lithospermum diffusum
- Lithospermum diffusa
Also from the Boraginaceae family:
- Nemophila (Baby Blue Eyes Flower)
- Virginia bluebells (Mertensia virginica)
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Size & Growth
The lithodora is described as a low-growing, evergreen shrub with blue and white flowers.
With the Heavenly Blue variety being very popular for its true blue flower colors and foliage color.
The flush of beautiful blue gentian colored flowers are a sight to see.
It grows to a height of 6″ – 12” inches and may spread over an area of 24″ – 48” inches.
Flowering and Fragrance
The flowers bloom time is from early spring or late spring to early or late summer, through May and August with white and deep blue flowers with reddish-purple veins.
The showy flowers are tiny, with 5 petals and are in a tube-like shape.
There is also some sporadic blooming during the fall growing season.
The branches are woody and prostrate with dense coverage of small, narrow leaves which are at most 1” inch long with a dark green color on top and a grey-green hue below.
The dark green leaves and stems are “hairy” on this perennial and retain its leaves even through the winter months.
Light & Temperature
In order to bloom properly, the plant requires partial sun to full sun in cool climate regions, and part shade or partial shade in hot regions, especially during the hottest part of the day.
It prefers a Mediterranean-ish climate and doesn’t thrive in hot, humid regions.
Lithodora grows in a USDA hardiness zone of 6-8.
Water Needs and Feeding
This garden plant is pretty low maintenance and doesn’t require frequent watering. However, it is important to ensure the soil does not dry out.
A thick winter mulch should be applied to protect plants and to encourage healthy growth.
Do not over-fertilize! If leaves start losing their rich green color, apply an acidic fertilizer on the shrubs following the label directions.
Soil & Transplanting
It grows best in a well-drained, moist, fertile, humusy acidic soil.
Although the acidic soil should be well-drained, it should never completely dry out.
It grows best on as a ground cover on slopes or in raised beds. Read our related article on Soil for Raised Beds.
Grooming and Maintenance
The center of the leaves may start browning after the flowers bloom.
Furthermore, too much shade and old age may make the growth of the Lithodora diffusa more “open”.
In either of these cases, prune the plant to prevent overspreading and to get rid of the decaying leaves to encourage healthy plant growth.
The plant has a tendency to spread and may need to be pruned regularly to prevent it from spreading too far and damaging other plants or crossing its assigned boundary.
How to Propagate Lithodora
- Obtain softwood tip cuttings of the plant during the warmer months when the plant is actively blooming, skip any parts of the stem which have browned since this is a sign of the plant getting old.
- Make sure cutting comes from a plant free of pests and diseases.
- Cuttings should be around 2″ – 3” inches long.
- Use a mixture of 50/50 perlite, peat moss and place the cuttings in a hole in the center.
- The plant should get a decent amount of sunlight (but not full sun).
- Keep the mix moist but not too wet.
- Ideally, allow the plant to grow until the roots fill up their pot before transferring them to your garden.
- This should take around a month if the pot is small.
- Once the plant is strong enough, you may plant it into your garden or in hanging baskets or wherever you please.
Lithodora Pest or Disease Problems
Lithodora isn’t likely to suffer from insect or disease problems.
The main thing to watch out for is aphids (sap-sucking insects), a major sign of your shrubs being affected by aphids is if the leaves are covered in sap.
The plant is deer resistant.
Is This Plant Toxic Or Poisonous?
The plant is reported to be non-toxic for all animals and people and is ideal for any garden, including in a house with pets and small children.
Is This Plant Invasive?
Unless it is growing among wildflowers and weeds, lithodora may spread out far, damaging other plants in the process.
It is generally grown on slopes to provide grown cover and should not be planted with other flowers or plants.
Suggested Lithodora Uses
Often, the lithodora is planted for aesthetic purposes and looks great in rock gardens.
Deer resistant Lithodora is also frequently used as a ground cover and for erosion control.
This plant prefers rocky beds and is ideal for beautifying slopes, banks, etc.