Lithodora Plants: How to Grow Lithodora

Lithodora diffusa is a hardy, evergreen ground cover plant. It's part of the Lithospermum genus of the Boraginaceae family and grows well in USDA zones six to ten. Lithodora is a native Mediterranean plant and doesn't grow as well in very hot regions. It requires full or partial sunlight in colder climates and partial shade in warmer areas.
Mature plants have thin green leaves year-round. Most varieties produce large numbers of tubular, heavenly blue flowers with five star-shaped petals. The bloom time starts at the end of spring and runs throughout the summer. Lithodora is ideal for gardeners who want to create a landscape with showy perennial plants, and it's perfect for filling gaps in rock gardens and along the edges of flowerbeds.

Lithodora plants are low-growing, reaching a maximum height of around ten inches. However, each plant can spread up to thirty-six inches, providing easy-to-maintain coverage with loosely entwined foliage.

• Start with cuttings. You can easily grow new lithodora plants from two to three-inch cuttings taken in the summer growing season. Select a healthy plant to take cuttings from, and choose younger green shoots as they'll thrive better than woody, brown stems.
• Choose the right soil. Lithodora generally grows best in acidic, sandy soil, although some varieties grow well in alkaline soil. Ideally, the soil should be moderately rich and have ample drainage. Avoid planting lithodora in clay soil, as it’s known to hold a large amount of water which can kill groundcover and negatively affect the health of the lithodora’s roots.
• Plant the cuttings. Once you've taken a cutting, you can remove the leaves from the bottom half of the stem and apply a rooting compound to the cut end. Planting the cuttings in equal parts peat moss and perlite, leaving the leafy part exposed, and moistening the soil slightly is usually the best way to ensure your cutting survives and grows into a healthy plant.
• Keep the cuttings in a warm, moist environment. When propagating lithodora cuttings, use a greenhouse. If you don't have one, you can cover the pots in a transparent plastic bag to protect the cuttings and allow some sunlight in, keeping in mind that placing the plant in full sun may dry out the plant and prevent it from propagating properly. Keeping the soil moist but not wet while you wait for roots to develop is usually best, and it can be useful to test the soil moisture to avoid overwatering.
• Repot the cuttings. Once the cuttings have roots, you can safely transfer each cutting to its own small seedling pot, and place them back in the greenhouse for around a month.
• Move your lithodora plants outside. You can plant your lithodora plants in your garden after exposing them to the elements for a couple of weeks. Ensure that anywhere you plant them has the correct soil type and light conditions for your chosen variety.
• Water regularly. Lithodora plants have relatively high water needs and don't do well in dry soil, although you should avoid overwatering them. Generally, it's best to aim for moist but not wet soil, as waterlogging could lead to root rot.
• Remove weeds. It's important to keep the area around your lithodora plants weed-free because weeds will compete with your plants for light and nutrients. Inspect your garden regularly and hand-pull weeds as soon as you notice them. You can also use a selective weed killer to deal with a more serious weed problem. However, you should avoid using nonselective herbicides, as they could kill your other plants.

Spring is the best time to prune your lithodora plants, but you can also cut them back in late summer when they’ve finished flowering to stop them from growing too large. Avoid cutting away more than a third of each plant, as over-pruning can cause them to die. Use sharp pruning shears and clean them thoroughly before use to avoid spreading disease or pests between plants. Take care to remove any straggly, blackened, or diseased areas to keep the plants healthy.

Many lithodora plants grow quite well without fertilizer, although it can help rejuvenate your plant if it looks yellow or unhealthy. You can apply a light, slow-release fertilizer for acidic soil over the winter and early spring. You could also consider adding manure or compost to enrich the soil.
If you live in a USDA hardiness zone five or colder, your lithodora plants may struggle in the winter. You can help them cope by mulching the soil around your plants in the fall to protect them from low temperatures later in the year.

Although Lithodora plants are reasonably resistant to pests, you can treat them with insecticidal soap or hot pepper wax if you notice common pests, such as aphids and whitefly. Occasionally, lithodora plants can develop an infection known as bacterial leaf spot that causes yellow-edged patches, sometimes with a red center.
Bacterial leaf spots can quickly spread to other plants, so pull up and dispose of any affected plants as soon as you notice signs of infection. You can reduce the risk of bacterial leaf spot by watering your plants as close to the soil as possible and avoiding getting the leaves and stems wet.

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