Leadwort: location, species & hardiness
Leadwort is one of the rare garden plants with naturally blue flowers. In October, its lovely blue flowers contrast beautifully with its wine-coloured foliage.
Given how rare blue flowers are, leadwort (Ceratostigma) is a real garden showstopper. Read on for a profile on the robust perennial as well as a guide to planting and caring for leadwort.
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Leadwort: flowering period and description
With fewer than 10 species, leadwort belongs to the Plumbaginaceae family and is also known as plumbago. While it is native to Southeast Asia and China as well as Africa, it shares its name with a close relative, the Plumbago genus, such as cape leadwort. Plumbago is a perennial shrub that reaches 25 to 100cm in height.
Leadwort begins sprouting between April and May and has hairy, ovate leaves that are arranged alternately. The star-shaped flowers grow in inflorescences and feature five sky-blue petals that widen outwards. As a late bloomer, leadwort is a popular insect destination between May and October. Bees, in particular, benefit from the late flowers for replenishing their winter stores. Once pollinated, leadwort seeds mature in pods that grow together in spiky seed heads and open when ripe. Birds cheerfully eat the pods, assisting leadwort in dispersing its seeds.
The most beautiful species
Most of the leadwort plants in our gardens are the same three species. Leadwort has not been bred much, so there are hardly any varieties.
Here are the most beautiful species to grow at home:
Griffith’s plumbago (Ceratostigma griffithii)
The creeping sub-shrub grows to a height of 20 to 80cm and provides excellent ground cover. Between July and October, Griffith’s plumbago parades an abundance of blue flowers. In autumn, the small leaves turn red and gold.
Hardy blue-flowered leadwort (Ceratostigma plumbaginoides)
Also known as blue ceratostigma, hardy leadwort is the most popular plumbago found in gardens. The herbaceous perennial only reaches a height of around 20 to 30cm, making it ideal to plant under other shrubs and trees. It spreads with runners that form a mat of stems and blue flowers, making it an excellent ground cover. Between August and October, hardy leadwort flowers in vivid shades of blue. Its foliage gradually turns burgundy in autumn, creating an exceptionally beautiful contrast to the blue flowers.
Chinese plumbago (Ceratostigma willmottianum)
The small deciduous shrub is also known as hardy plumbago and forms loose clumps between 80 to 125cm high. While Chinese plumbago’s autumn colours are less vibrant, the woody shrub keeps its yellow and orange foliage for a long time. Its flowers appear between August and October and are blue with a pale centre. Check out our other article for more beautiful autumn-flowering perennials.
Planting leadwort: location and method
Leadwort grows best in well-drained soil with a pH between 7 and 9. While it prefers a chalky and stony substrate with some humus, it can also grow in sandy or loamy soils. Leadwort is drought-tolerant and thrives in sheltered, warm locations with full sun or partial shade. It can establish itself well beneath other plants, at woodland edges and in stony terrain such as rock gardens.
Plant leadwort with other spreading perennials to create splendid floral borders. Various geraniums (Geranium) and members of the Lamiaceae family such as betony (Stachys officinalis) as well as spurge (Euphorbia), stonecrop (Sedum) and catmint (Nepeta) are excellent companion plants. Spring bulbs like daffodils (Narcissus) and tulips (Tulipa) are also excellent companions because they have already retreated back into the ground by the time leadwort sprouts.
Plant new plants outside from March onwards as leadwort is sensitive to frost. Leave 25 to 40cm space between leadwort and other plants. When growing leadwort for ground cover, plant around 16 specimens per square metre for dense coverage. Plant the plants in the soil at the same depth as they were in the pot. It can take up to three or four years for hardy blue-flowered leadwort to properly establish itself in a new place.
Leadwort grows well in pots with at least 20L of soil. Place them on the balcony, terrace or in window boxes for a beautiful pop of colour in late summer and autumn. Fill the bottom of the container with gravel, sand or clay pebbles to provide good drainage even in heavy rain, as leadwort does not tolerate any waterlogging. Fill with a peat-free potting mix rich in nutrients and compost, such as our Plantura Organic Flower Compost. The fertilised substrate is perfectly tailored to the needs of flowering plants, providing everything they need during the first couple of months following planting.
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The right care
Leadwort is a low-maintenance plant that needs little care. Water it in the summertime during prolonged dry spells, especially if planted in sandy, shallow and stony soils. Work some compost or fertiliser into the soil when leadwort starts sprouting in spring to encourage it to grow and bloom vigorously. We recommend using our Plantura Flower Food for this, as it specially formulated for flowers. Simply spread it thinly around the plant from March once the soil is frost-free. Water well to quickly release the nutrients into the soil.
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Since herbaceous leadwort withers above ground in winter, it will need pruning in spring. Cut back the dead stems completely to make room for new shoots. Prune all diseased, frost-damaged or dead shoots off the shrubs. Leadwort is generally resistant to diseases and pests. However, powdery mildew may strike in cool and damp spring weather. Remove affected leaves immediately.
Is leadwort hardy?
All three leadwort species mentioned are hardy throughout most of the UK (-5 to -10°C) and the hardy blue-flowered leadwort, as the name suggests, is the hardiest of them all and hardy even in severe winters in the UK (-10 to -15°C). Even so if you want to give it a little extra protection in winter it will not complain, spread a layer of leaves or pine branches around it. Luckily, even slightly frost-damaged plants will reliably sprout again in spring. Protect potted leadwort from heavy frosts with hessian cloth, leaves and pine branches or overwinter it in a frost-free place.
Propagating leadwort
You can easily propagate hardy blue-flowered leadwort by simply cutting off runners with roots and transplanting them. Take cuttings from woody leadwort plants in summer. Leadwort loves to creep along the ground, so it is easy to find shoots that have grown roots on contact with the ground, which is known as layering. Remove them from the parent and transplant them to a suitable location.
Is leadwort poisonous?
There is no evidence that leadwort is poisonous to humans or animals. Its name is a reference to the flowers’ lead-blue colour and has nothing to do with any toxicity. But since leadwort is not edible, do not eat any parts of the plant.
Another herbaceous perennial for semi-shady spots and woodland edges is the extraordinary toad lily (Tricyrtis). Discover the exotic flower’s requirements and find out how you can successfully grow it in your garden.
