The ginkgo is a remarkable tree, dating back to before the time of the dinosaurs so sometimes referred to as a "living fossil". It is one of the gymnosperms, meaning their seeds are unprotected by an ovary or fruit. Conifers and cycads are also gymnosperms and while their seeds are usually borne in cones, ginkgo produces its seed at the end of short, knobbly stalks that give the tree a distinctive silhouette in the winter.
Ginkgo is a monotypic genus — only one species. This is G. biloba, a relatively tall tree at around 25m with fan-shaped and often bilobed leaves. The leaf shape looks similar to the tiny leaves of the maidenhair fern, explaining ginko’s common name, the maidenhair tree. The foliage is mid-green but turns a buttery yellow in autumn. It has a conical habit when young but becomes more irregular with time.
Male forms are preferred because the females produce smelly and messy fruits that splatter in autumn. However, it takes 20-35 years for a tree to reach maturity and reveal its gender. Male clones such as ‘Tremonia’ or ‘Mayfield’ are available but they can be in short supply and command a higher price.
Many dwarf or compact varieties have been bred that are suited to small gardens or container planting. These include ‘Troll’ Award of Garden Merit (AGM) and ‘Mariken’ AGM, which form dense balls of foliage atop a trunk. They can live in pots for many years, with minimal attention and occasional feeding.
Having survived for more than 200 million years, it is no surprise that ginkgos are not difficult to grow. They are completely hardy and suit most positions in sun or shade. They can be slow to establish so prepare the planting hole well with humus and top dress with a fertiliser. Choose a warm, sheltered spot that is never waterlogged and do not plant too deep — some of their roots like to be close to the surface.
The species and taller varieties can be seen in parks and gardens and some adventurous tree officers select them as street trees. They are known to cope well with the urban climate and air pollution. There are few problems associated with ginkgo. Trees grown in humid, sheltered gardens might see mild attacks by mealy bug or soft scale, but diseases rarely affect this plant.
What the specialists say
Mike Glover, managing director, Barcham Trees, Cambridgeshire
"Very common about 200 million years ago, this marvellous gymnosperm is making a comeback as an urban tree due to its no-nonsense toughness. It can cope with traffic exhaust as well as reflected heat and light in our urban environments. Reintroduced into the UK in 1754.
"This large, conical tree remains relatively narrow if the central dominant leader is retained. It is a good choice for parks and avenues, tolerating paved areas well. It has
a deep root system and curious fan-shaped leaves. Female plants fruit after 35 years or so.
Male clones such as ‘Mayfield’, ‘Saratoga’ and ‘Tremonia’ are disappointing in their lack of vigour. ‘Lakeview’ and ‘Princeton Sentry’ are the pick of the male types but remain difficult to grow, rarely come to market and command a tidy premium."
Bruce Jordan, managing director, Big Plant Nursery, West Sussex
"G. biloba and its cultivars are appealing in many ways. They have an interesting leaf form, beautiful golden autumn colour, prehistoric ancestry and the ability to withstand adverse conditions. They are particularly useful in urban planting, being tolerant of both soil and air pollution, as well as enjoying the slightly warmer microclimate. Being a deciduous conifer, the leaves lock up airborne pollution, helping clean the environment. Soft non-invasive root systems also make them safe to plant near buildings and pathways.
"There are many interesting cultivars but for landscape planting the best choice is probably one of the upright forms. ‘Princeton Sentry’ has a narrow but open, not too dense, framework and ‘Tremonia’ has a silhouette like the Italian cypress. We have been trying top-grafted varieties ‘Troll’ and ‘Mariken’, which form dense foliage balls when grafted on G. biloba trunks — good for garden designers.
"Ginkgo can be slow to establish so are best treated to good planting conditions (compost and top dressing with fertiliser), avoiding waterlogging and competition from grass or weeds. Always make sure not to plant them too deep. They will do better in the warmest part of the garden. We find pruning, formative only, is best done in late winter. We like to feed them organically using seaweed and poultry-based top dressing. They are not fussy but respond well to regular feeding."
John Robinson, consultancy director, Greencut Horticulture, Kent
"We often recommend the ginkgo species as an interesting alternative when assisting clients with tree replanting. They are very tolerant of pollution and reflect heat and light in an urban environment, making a very good choice for parks, avenues or larger gardens, also working well in paved areas due to deep rooting.
"I remember working high in the canopy of a very large G. biloba in a council-owned park in Maidstone, Kent, that despite offering exceptional amenity value had unfortunately developed several tight compression unions at several branch forks, to which this species is prone. In extreme cases these poor unions can result in major failures, damaging the natural form of the tree and increasing the health and safety risk for users of the area below the tree.
"This particular tree required the installation of five non-invasive flexible restraint systems to support these unsatisfactory unions. While minimising the risk of branch failure, such work should be followed by an annual inspection from ground level using binoculars and a five-yearly re-inspection for a detailed aerial inspection.
"The positive benefits and interest of the Ginkgo far outweigh the negative factors. This remarkable tree is known as a ‘living fossil’, the sole survivor of an ancient group of trees that date back to beyond the time of the dinosaurs."
Species and varieties
G. biloba, or the maidenhair tree, is a deciduous tree with fan-shaped and often bilobed leaves that turn clear yellow in autumn. Conical when young but becomes more irregular in habit with age. Female produces unpleasantly scented dull-yellow fruits. Height: 25m.
G. biloba ‘Autumn Gold’ AGM is a striking male selection from America with mid-green leaves turning a beautiful golden yellow in autumn. It becomes a small tree with a broad pyramidal shape. Can be grown in a container. Height: 4m.
G. biloba ‘Chi Chi’ (syn. G. biloba ‘Tit’) becomes a large, branching shrub. It grows slowly and once established develops ornamental, rounded growths on the trunk. The leaves are green through summer, turning gold and bronze in autumn before falling. Likes a nice sunny position and does well in urban areas. Height and spread: 2.5-3m.
G. biloba ‘Jade Butterflies’ AGM is a wonderful introduction from China. It has large rounded leaves that are produced in pairs, often in perfect symmetry, so that they actually resemble a butterfly. Can be planted into a container or grown as a specimen tree. Height 4.5m. Spread: 2.5m.
G. biloba ‘King of Dongting Mountain’ is a very slow-growing female selection that can produce seed if successfully pollinated by a male ginkgo. It has large leaves that are green in the summertime, then turning shades of gold and bronze in the autumn. Suits container growing and areas with limited space. Height and spread: eventually 8-10m by 6m, but only 2-2.5m by 1-1.5m within 10 years.
G. biloba ‘Mariken’ AGM is a very recent introduction, discovered in the Netherlands in the mid 1990s. A dwarf form that grows very slowly and is highly compact, eventually forming a spherical mass of leaves. One of the best of the dwarf ginkgos for container cultivation. Height and spread: 1.5m.
G. biloba ‘Princeton Sentry’ AGM is a male, fastigiate variety with a remarkably straight stem and uniformly spaced upward-growing branches. Slow-growing, particularly when young. Suits small gardens and as a street tree. Requires a site with plenty of light. Height: 15-20m. Spread: 6m.
G. biloba ‘Saratoga’ AGM is an excellent selection from the famous Saratoga Research Institute in America. It has a compact, upright habit and distinctive drooping, narrow foliage that looks like half-open fans. Recommended for hedges and for container cultivation. Height: 12m. Spread: 10m.
G. biloba ‘Tremonia’ is a German selection that features a narrow fastigiate form and heavily textured blue/green foliage. Recommended for small gardens, where it will take up very little room or could be planted in groups. Height: 10-12m. Spread: 5m.
G. biloba ‘Troll’ AGM is a rarely found but sought-after, extremely slow-growing dwarf tree with
dark-green ruffled leaves turning butter yellow in autumn. Its compact, bushy growth means it
can be grown as a container plant on the patio. Height and spread: 1m.
Thank you to Floramedia, which supplied the images for this article from its photo library