Plant profile: umbellifers
As loved by pollinators as they are by gardeners and designers, this vast group of plants creates a froth of delicate flowers and foliage to suit many garden styles
Nurserywoman Marina Christopher admires the flat-headed inflorescence and ferny foliage of the pollinatorfriendly Apiaceae family
The Apiaceae family is so vast no single feature could do it justice, so here I’m going to concentrate on one subfamily: Apioideae, familiar to many in the forms of vegetables such as carrots, herbs including dill and coriander, and the frothy mass of small white flowers that wave aloft over ferny green foliage along hedgerows. This diaphanous haze is the flowering peak of the humble cow parsley (Anthriscus sylvestris), sometimes referred to as Queen Anne’s lace.
All are known as umbellifers, characterised by the formation of their flowers in umbels (meaning umbrella-like), a flat-topped inflorescence supported by a pedicel (a stem supporting a flower or seed), which all originate from the same point on the main stem. Other characteristics include hollow internodes (the space between two leaf joints), aromatic volatile oils emitting a herby odour and, in many genera, finely dissected foliage. Individual flowers are usually cream, white or yellow and small but so numerous they make substantial flowerheads. Many umbellifers are monocarpic, meaning they die after flowering but set prodigious quantities of seed. They may be annual, biennial or short-lived perennials.
My interest in umbellifers stems from an ecologist’s vantage point. They are an important food source for the non-specific pollinators, such as flies, beetles, moths and hoverflies, which are vital for encouraging insect biodiversity and unlike bees aren’t attracted by a flower’s colour but by its foetid smell. The hollow stems also provide valuable overwintering accommodation for many beneficial insects, which burrow into the plant above the solid node and are well protected from the elements. From an ornamental viewpoint, their attractive dissected foliage is a good foil for border perennials, and architectural umbellifers, such as Molopospermum peloponnesiacum and Peucedanum verticillare, give structure and height. Purple-suffused foliage and flowers have occurred several times in the wild and eagle-eyed collectors have propagated and distributed them. Notable are Anthriscus sylvestris ‘Ravenswing’ and more recently the darker Anthriscus sylvestris ‘Dial Park’, discovered in Olive Mason’s Worcestershire garden of the same name, with purple-black foliage and white- or pink-tinged flowers. Angelica sylvestris ‘Vicar’s Mead’ and Angelica sylvestris ‘Ebony’ have pink umbels. Pink-flowered umbellifers also include Pimpinella major ‘Rosea’, Pimpinella rhodantha and Chaerophyllum hirsutum ‘Roseum’. Purple-flowered Angelica gigas is grown for herbal medicine in Korea but makes a handsome garden specimen.
Annual umbellifers are increasingly popular with white-flowered Orlaya grandif lora and Ammi majus the most familiar and used to great effect in the borders of Great Dixter. Dill, Anethum graveolens, and the easier to grow false fennel, Ridolfia segetum, are yellow-flowered annuals and Daucus carota ‘Dara’ and Daucus carota ‘Purple Kisses’ are two purple-flowered ornamental carrots.
Monocarpic umbellifers, such as angelicas, can create bold statements in a border but disappear after flowering. Cutting off the flowerheads before seeds set may cause offsets to develop at the base of the plant extending their life but is unreliable. An architectural perennial, such as Molopospermum peloponnesiacum, could be a better option; it is hardy and a dramatic subject, hailing from Spanish mountainsides where the deep taproot uses moisture from underground. Cenolophium denudatum, a perennial, white-flowered umbellifer, naturalises well in dappled shade and has been much vaunted in recent display gardens at the RHS Chelsea Flower Show. Zizia aurea or golden alexanders hails from North America and is valuable for dappled shade in moisture-retentive soil, as is a favourite of mine, the delicate Taenidia integerrima, a greenish-yellow-flowering perennial that can tolerate dry soils.
Umbellifers have interesting and attractive foliage, and contrast well with different flower shapes. They provide nectar and pollen to thousands of insects, food for seed-eating birds and their hollow stems offer valuable overwintering accommodation for many beneficial insects. What’s not to like? n
• Author Marina Christopher is a nurserywoman who runs Phoenix Perennial Plants.
Her recommendations for the best umbellifers can be found over the next five pages.
Zizia aurea
Known as golden alexanders, this yellowflowered, native American perennial prefers moistureretentive soil in shade or sun. Flowers for several weeks and grows almost as broad as it is tall. 60cm. RHS H7, USDA 3a-8b.
Cultivation
Most cultivated umbellifers are grown from fresh seed but some are difficult to germinate taking more than one season to emerge. The seeds contain oils that inhibit germination and which naturally break down by freeze then thaw in winter, resulting in a plethora of cotyledons emerging at what may seem an inopportune time of year. Gardeners are often recommended to place seed in the fridge, but germination is far more successful if seeds are sown in pots in the autumn and left in a cold frame or unheated glasshouse to receive the see-sawing temperature changes of winter weather. Annuals such as Ammi majus and Daucus carota germinate readily from spring sowing but Orlaya grandiflora germinates most successfully in autumn and is more erratic if sown early in the year.
Although many umbellifers may be unpredictable in their germination habits, some are almost too eager to reproduce given favourable conditions. Carpets of Angelica archangelica, Foeniculum vulgare and Smyrnium perfoliatum can be plagues in some gardens whereas other growers find them difficult to establish. The carroty smell of the seeds is very attractive to voles and mice so it is important to keep them away from seed pots.
Long taproots are characteristic of this family allowing them to survive in dry, harsh conditions once the root has developed sourcing moisture and minerals from deeper levels. The root grows quickly so it is best to move seedlings into deep plug trays or pots as soon as possible. Most umbellifers have slim, linear cotyledons that are large enough to handle easily and I prefer to prick out germinated seedlings before or just as the first true leaves have emerged when the root is still reasonably short and is not damaged by the move.
Orlaya grandiflora, Visnaga daucoides, Daucus carota and Seseli gummiferum grow in poor, often infertile waste ground. Growing them in rich garden soils makes them larger and lusher but with changing climatic conditions, notably more wind events, there is more bruising of the foliage and root rock releasing the characteristic carroty aroma. Knowledge of their natural habitat and growing them in poorer conditions will improve their longevity. Seseli gummiferum is reasonably perennial in lean conditions but acts as a biennial when grown in richer soils.
Taprooted plants are often good for root cutting propagation. Umbellifers are no exception and more are found to develop from root cuttings, such as Peucedanum verticillare, Meum athamanticum and Mathiasella bupleuroides, an excellent recent introduction from Mexico that has proved relatively hardy in many southern gardens.