Why is the astrantia or masterwort (Astrantia major and other species) so little known? It has everything it takes to please the home gardener: beautiful star-shaped flowers in an interesting range of colors, a long blooming period, attractive foliage, excellent cold hardiness, ease of cultivation, reasonable availability in nurseries, etc. But it remains little known to the average gardener. Only the most informed gardeners seem to appreciate it and use it.
Maybe it simply lacks publicity? If so, this article might help!
Common Names: astrantia, masterwort
Origin: Europe and Caucasus
Dimensions: 18 to 36 inches x 15 to 24 inches (45-90 cm x 40-60 cm), depending on the variety
Exposure: sun, partial shade, shade
Soil: rich and humid
Flowering period: July-September
Propagation: division, seeds
Uses: mixed flower bed, mass planting, naturalization, groundcover, shade garden, wildflower meadow, pond edge, cut flower, butterfly garden
Associations: astilbes, hostas, ferns, Siberian irises, lungworts
Hardiness zone: 3
The genus Astrantia is a rather small one, with only 7 to 10 species. Of these, only three are commonly cultivated (four if you count the interspecific hybrid varieties as a species): great masterwort (A. major), by far the most common, carnic masterwort (A. carniolica), a smaller species and, yet again, great masterwort (A. maxima)—it’s not my fault if the two plants have the same common name! —, like A. major, but with larger leaves. I’m finding most gardeners these days have abandoned the original English name, masterwort, and are simply using astrantia is the common name.
Astrantia is a somewhat abnormal member of the Apiaceae, formerly called Umbelliferae: the carrot family. It’s renowned for its large umbels of tiny flowers, but astrantia flowers don’t appear at first glance form an umbel (dome), but rather have star-shaped flowers. In fact, the name Astrantia comes from astrum, Latin for star. If you look carefully, however, you’ll see that what appears to be a single flower is actually a small umbel surrounded by colorful bracts. It’s the small “buds” in the center of the little umbel that are the real flowers, grouped together much like a pincushion (for those of you who still remember what a pincushion is!). The individual florets would be totally insignificant on their own, but the whole inflorescence, with its pincushion center surrounded by pointed bracts, is very attractive. The “flowers” (actually inflorescences) can be green, white, pink or red, often veined in green.
The inflorescences are carried on thin but solid stems. They branch repeatedly ensuring there is repeat bloom throughout the summer, often well into September.
The leaves are also attractive. Palmate, toothed and with several lobes, they look vaguely like a maple leaf, or maybe a star. Again, the signification of the botanical name Astrantia is apparent.
In nature, astrantias grow in open forests and wet meadows. They are fairly common plants from western Europe to the Caucasus, though mostly at high altitudes and in the North, because they don’t appreciate the hot summers of the South. They’ll do bestwhen you grow them under similar conditions: partial shade or, if cultivated in full sun, in soil that is always a bit moist. They’ll grow and bloom in shade too, but their blooms don’t last as long. In hot, sunny spots, a thick mulch (3 to 4 inches/7 to 10 cm) over the root zone will help keep the soil moist and cool. Astrantias tolerate drought when well established, but it will likely shorten their flowering period.
My experience is that astrantias are at their best in partial shade. They bloom perfectly well in early summer in sun and shade, but the flowers tend to peter out by mid-August. In partial shade, though, they just bloom on and on until well into September. On the other hand, if you can keep full-sun plants cool and moist … wow! That will give you extra flower power. Remember that morning sun is cooler than the afternoon sun: that might help you find the best spot.
And yes, astrantias can cope with dry shade (spots where the root competition of overhanging trees makes gardening difficult). In fact, they will self-sow in spots completely dominated by tree roots, saving you the effort of planting them.
Over time, a typical astrantia will grow and expand due to underground rhizomes. However, the rhizomes are short, so the plant just forms a larger and larger clump without becoming invasive. After 7 to 10 years, it may be necessary to divide it to keep it under control. And division is the main means of propagation. You can divide it in any season, as long as the soil is not frozen, but normally it’s something you’d carry out in spring or fall.
I mentioned that astrantias are not invasive … by rhizomes. But they do self-sow, usually modestly, especially in cool or somewhat shaded places. If you are not interested in specific cultivars, you can just let them spread around. Astrantia cultivars are not true to type, however, and seedlings won’t be exactly identical to their mother. In fact, the colors tend to slowly change over time, each new generation varying a bit more from the original. Red ones give seedlings that become more and more pink over the years, while the pinks tend to return to shades closer to white. Eventually, when you have space to let them resow that is, they can create a beautiful multicolored carpet.
If you are a purist and want to keep the cultivars as is, just don’t let them resow. Remember that although spontaneous plants may look a lot like their parent, they are in fact always a bit different. So you can’t label seedlings of ‘Hadspen Blood’ as ‘Hadspen Blood’, for example, but perhaps Hadspen Blood seedling.
A good mulch will be enough to prevent too much self-sowing: astrantias simply can’t resow when the mulch is thick!
You can also sow astrantias from seed and indeed, there are a few seed-sown strains available that come fairly true: ‘Rosensinfonie’ (Rose Symphony), ‘Primadonna’ (Ruby Stars) and ‘Ruby Cloud’, for example. A 2- to 4-week period of cold treatment is necessary to stimulate good germination.
So Much Choice!
There are over 40 cultivars of astrantia, although I doubt you will find all 40 in the same nursery. Many are fairly similar and all are good plants, so just pick your favorite colors from whatever is offered and you’ll probably be delighted. Here, though, are a few that I particularly like:
A. major ‘Abbey Road’: deep purple-red flowers with a white base. Dark purple stems. Flowering period: July-September. 24 inches x 18-20 inches (60 cm x 45-50 cm). Zone 3.
A. x ‘Buckland’: pink florets and silvery-white bracts with green veins. Flowering period: July-September. 24 inches x 24 inches (60 cm x 60 cm). Zone 3.
A. major involucrata ‘Shaggy’ (A. major involucrata ‘Majorie Fish’): Large white flowers with green veins. Long blooming. Flowering period: July-September. 32 inches x 18 to 20 inches (80 cm x 45-50 cm). Zone 3.
A. x ‘Hadspen Blood’: Very dark red. New leaves tinged red. 28 to 30 inches x 18 to 20 inches (70-75 cm x 45-50 cm). Zone 3.
A. major ‘Magnum Blush’: extra-large bicolored pink and white flowers. Very chic! Flowering period: July-September. 24 to 26 inches x 18 to 20 inches (60-65 cm x 45-50 cm). Zone 3.
A. x ‘Roma’: large bright pink flowers. The bracts are white at the base, pink at the tip. Flowering period: July-September. 28 inches x 18 to 20 inches (70 cm x 45-50 cm). Zone 3.
A. major ‘Vanilla Gorilla’: flowers silver pink, foliage abundantly variegated in creamy white. Foliage color more durable than the classic variegated astrantia, ‘Sunningdale Variegated’, whose foliage tends to return to pure green during the heat of the summer. Flowering period: July-September. 16 to 24 inches x 18 to 20 inches (40-60 cm x 45-50 cm). Zone 3.