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:
Related: How Do You Care for Echiums?
Size and Growth
The lithodora is described as a low-growing, evergreen shrub with blue and white flowers.
The Heavenly Blue variety is very popular for its true blue flower colors and foliage color.
The flush of beautiful blue gentian colored flowers is a sight to see. It grows to a height of 6″ to 12” inches, but a single plant may spread over an area of 24″ to 48” inches wide.
Flowering and Fragrance
The bloom time of Lithodora flowers 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 five petals, and are tube-like.
There is also some sporadic blooming during the fall growing season.
The branches are woody and prostrate with dense coverage of small, narrow hairy 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 and Temperature
To bloom properly, the Lithodora plant requires partial sun to full sun in cool climate regions and partial shade in hot regions, especially during the hottest part of the day.
In hot climates, this plant will grow well in the afternoon shade.
Moreover, it prefers a Mediterranean-ish climate and doesn’t thrive in hot, humid regions.
Lithodora grows in a USDA plant hardiness zone of 6 to 8, making it perfect for gardens.
During winter months, apply a thick layer of mulch to insulate the plant’s root ball and protect them from cold winter temperatures.
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 encourage healthy growth.
Do not over-fertilize! If leaves start losing their rich green color, apply an acidic fertilizer on the shrubs in early spring or late winter. Don’t forget to follow the label directions.
Also, avoid using granular fertilizers, especially near the plant crown and foliage, as they can cause fertilizer burns.
Soil and Transplanting
It grows best in acidic, well-drained soil but may also thrive in moist, fertile, humusy soil. Remember that this plant may grow in sandy soil but cannot tolerate clay soil.
Although the acidic soil should be well-drained, it should be never completely dry out.
It grows best as a ground cover on slopes or in raised beds.
It’s also recommended to mulch your lithodora plant to retain soil moisture and soil temperatures.
Related: Soil for Raised Beds.
Grooming and Maintenance
The center of the leaves may start browning after the flowers bloom. So you must cut back the plant after the flowering period. This will also help keep the lithodora in the desired size.
Removing unwanted tall or leggy growth is also a must to create a more neat appearance.
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 tends to spread and may need to be pruned regularly to prevent it from spreading too far, damaging other plants, or crossing its assigned boundary.
How to Propagate Lithodora
Lithodora plants can be propagated by semi-hardwood cuttings or seeds.
Here’s what you need to do to propagate by semi-hardwood cuttings.
- Obtain semi-hardwood cuttings of the plant during the warmer months when the plant is actively blooming, and skip any parts of the stem which have been 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″ to 3” inches long.
- Use a mixture of 50/50 perlite and 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 in your garden or hanging baskets, or wherever you please.
Lithodora Pest Or Diseases
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.
Another good thing is this plant is deer resistant.
However, watch out for root rot, which can attack the plant’s roots, causing stunted growth and yellow foliage. Overwatering could cause this problem.
Another disease to look out for is bacterial leaf spots, which are broad, translucent spots with a yellowing edge.
If you suspect that you have infected plants in your garden, it’s best to remove them to prevent the spread of infestation or disease.
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. It makes an excellent choice for window boxes or containers.
For your landscape design, position your lithodora in front of taller plants for optimal coverage.
Deer-resistant Lithodora is also frequently used as a ground cover and for erosion control.
Moreover, this perennial plant prefers rocky beds and is ideal for beautifying slopes, banks, etc.