The Lithodora (Lithodora diffusa, Lithodora spp.) is a low-growing floral ground cover that looks great beside paths, around the margins of flower borders, and in rock gardens. It's also great in window boxes or pots. This is a hardy plant that produces small, brightly blue, star-shaped blooms frequently from late spring to mid-to late summer, but flowering is more erratic later in the season. In more southern locations with mild winters, it grows profusely and its dark-green leaves stay evergreen all year. A single plant may grow to be as tall as six to ten inches and as broad as 24 to 36 inches.
How to keep Lithodora Zahnii.
Water
Water freshly planted Lithodora thoroughly at least once a week to promote deep root growth. Stick your finger into the soil to see whether it is still moist one inch below the surface. Allow the soil to dry out or grow wet; overwatering may also promote root rot. One inch of rain every week should be plenty.
Temperature
While some gardeners have successfully overwintered some cultivars of this Mediterranean native in USDA Zone 5 or allowed it to survive in Zones 9 and 10, this herbaceous perennial is only hardy in Zones 6 through 8. It dislikes excessively hot and humid weather.
Fertilizer
Lithodora does not need fertilizer in general until the leaves become light green-yellow, indicating a nutritional deficit. Use an acid-loving plant fertilizer, such as rhododendron or azalea, and avoid applying granular fertilizers near the plant crown or leaves, as these might cause fertilizer burn. Use a diluted slow-release fertilizer instead.
Pruning
When trimming Lithodora, there are various factors to consider. Cold winter temperatures may cause the plant to develop straggly and destroy the stems or leaves. Wait until early spring to trim it, as you would any other evergreen. Remove any blackened leaves that may hinder future growth or illness. After the blooming time finishes in mid to late summer, the plant may be pruned back to freshen it and maintain the ideal size. Remove any overgrown or leggy growth.
Botanical profile.
- Plant Type
- Herbaceous flowering perennial groundcover
- Genus
- Lithodora
- Family
- Boraginaceae
- Hardiness Zone
- 6-8
- Bloom Time
- Early spring through mid to late summer
- Native Area
- Europe (The Mediterranean, northwestern France, southern Greece, Algeria and Turkey)
