Ginkgo biloba
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Ginkgo (Ginkgo biloba) also spelled gingko, also known as the Maidenhair Tree after Adiantum, is a unique species of tree with no close living relatives. It is one of the best-known examples of a living fossil, because Ginkgoales other than G. biloba are not known from the fossil record after the Pliocene.[1][2]
Ginkgos are very large trees, normally reaching a height of 20–35 m (66–115 feet), with some specimens over 50 m (164 feet). The tree has an angular crown and long, somewhat erratic branches, and is usually deep rooted and resistant to wind and snow damage. Young trees are often tall and slender, and sparsely branched; the crown becomes broader as the tree ages. During autumn, the leaves turn a bright yellow, then fall, sometimes within a short space of time (1–15 days). A combination of resistance to disease, insect-resistant wood and the ability to form aerial roots and sprouts makes ginkgos long-lived, with some specimens claimed to be more than 2,500 years old.
Ginkgo is a relatively shade-intolerant species that (at least in cultivation) grows best in environments that are well-watered and well-drained. The species shows a preference for disturbed sites; in the "semi-wild" stands at Tian Mu Shan, many specimens are found along stream banks, rocky slopes, and cliff edges. Accordingly, Ginkgo retains a prodigious capacity for vegetative growth. It is capable of sprouting from embedded buds near the base of the trunk (lignotubers, or basal chi chi) in response to disturbances, such as soil erosion. Old individuals are also capable of producing aerial roots (chi chi) on the undersides of large branches in response to disturbances such as crown damage; these roots can lead to successful clonal reproduction upon contacting the soil.
Ginkgo branches grow in length by growth of shoots with regularly spaced leaves, as seen on most trees. From the axils of these leaves, "spur shoots" (also known as short shoots) develop on second-year growth. Short shoots have very short internodes (so they may grow only one or two centimeters in several years) and their leaves are usually unlobed. They are short and knobby, and are arranged regularly on the branches except on first-year growth. Because of the short internodes, leaves appear to be clustered at the tips of short shoots, and reproductive structures are formed only on them (see pictures below - seeds and leaves are visible on short shoots). In Ginkgos, as in other plants that possess them, short shoots allow the formation of new leaves in the older parts of the crown. After a number of years, a short shoot may change into a long (ordinary) shoot, or vice versa.
The leaves are unique among seed plants, being fan-shaped with veins radiating out into the leaf blade, sometimes bifurcating (splitting) but never anastomosing to form a network.[3] Two veins enter the leaf blade at the base and fork repeatedly in two; this is known as dichotomous venation. The leaves are usually 5–10 cm (2-4 inches), but sometimes up to 15 cm (6 inches) long. The old popular name "Maidenhair tree" is because the leaves resemble some of the pinnae of the Maidenhair fern Adiantum capillus-veneris.
Leaves of long shoots are usually notched or lobed, but only from the outer surface, between the veins. They are borne both on the more rapidly-growing branch tips, where they are alternate and spaced out, and also on the short, stubby spur shoots, where they are clustered at the tips.
In some areas, most intentionally planted Ginkgos are male cultivars grafted onto plants propagated from seed, because the male trees will not produce the malodorous seeds. The popular cultivar 'Autumn Gold' is a clone of a male plant.
Ginkgos adapt well to the urban environment, tolerating pollution and confined soil spaces.[4] They rarely suffer disease problems, even in urban conditions, and are attacked by few insects.[5][6] For this reason, and for their general beauty, ginkgos are excellent urban and shade trees, and are widely planted along many streets.
Ginkgos are also popular subjects for growing as penjing and bonsai; they can be kept artificially small and tended over centuries. Furthermore, the trees are easy to propagate from seed.
| Standard Cyclopedia of Horticulture |
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Ginkgo (Chinese name). Syn., Salisburia. Often misspelled as "Gingko", and also known as the Maidenhair Tree. Ginkgoaceae, one of the segregates from the Coniferae. One species in northern China and Japan, the sole remainder of a more numerous tribe in geologic time; now widespread as a street and park tree and also prized for the edible seeds. Tall tree, with wedge-shaped deciduous lvs.: fls. small and mostly dioecious; pistillate fl. solitary, the single naked ovule ripening into a drupe; staminate fls. in slender, loose catkins: fr. a drupe about 1 in. diam., containing a very large lenticular seed or kernel. Ginkgo biloba, Linn. (Salisburia adiantifolia, Smith). Ginkgo. Maidenhair Tree. Kew Tree. A straight, sparsely branched, usually slender tree, attaining a height of 60-80 ft.: lvs. 3-5,1-clustered, fan-shaped, divided at summit, with thickened margin, striated on both sides with numerous parallel veins: fls. dioecious; male catkins slender, stalked; females on long footstalks, in pairs, of which one usually aborts: fr. a drupe, consisting of an acrid, foul-smelling pulp surrounding a smooth, angular oval, cream-colored, thin-shelled, sweet-kerneled nut.—The ginkgo was intro. to Amer. early in the last century; it is generally successful on good soil in the eastern states as far north as E. Mass, and Cent. Mich., and along the St. Lawrence River in parts of Canada. It is of special value for solitary planting to secure picturesque effects. It is considerably planted in Washington, D. C., where it is growing in esteem as a street tree because of its upright habit and freedom from insect injury. Easily prop, from seed, stratified in autumn; varieties by budding and grafting. Several horticultural forms are recognized, including laciniata, pendula and variegata. The foul odor of the ripe frs., which continue to mature and drop during a period of some weeks, constitutes the chief objection to the species as a street tree, or near dwellings, and suggests the advisability of prop, from staminate trees by grafting or budding, for planting in such locations. The kernels, which have a sweetish, slightly resinous flavor, are highly esteemed for food in China and Japan, and are gathered from fruiting trees in Washington for such use by Chinese laundry- men. The word Ginkgo seems to be pronounced with a hard initial G in the orient, but in English a soft G should be used. The name is often spelled Gingko, but the other spelling is that used by Linnaeus. CH
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Cultivation
It is hardy to zone 4. It is in flower from April to May, and the seeds ripen from October to November. The flowers are dioecious (individual flowers are either male or female, but only one sex is to be found on any one plant so both male and female plants must be grown if seed is required) and are pollinated by Wind. The plant is not self-fertile.
The plant prefers light (sandy), medium (loamy) and heavy (clay) soils and requires well-drained soil. The plant prefers acid, neutral and basic (alkaline) soils. It cannot grow in the shade. It requires dry or moist soil and can tolerate drought. It can tolerate atmospheric pollution.
Succeeds in most soil types so long as they are well-drained[117, 200, 202], though it prefers a rather dry loam in a position sheltered from strong winds[11]. Some of the best specimens in Britain are found growing on soils over chalk or limestone[185]. Plants flower and fruit more reliably after hot summers or when grown in a warm sunny position[202]. Established plants are drought resistant[117], they also tolerate atmospheric pollution[117, 200]. Plants can grow in poor hard-packed soil, making the male forms good candidates for street planting[229]. Trees are often used for street planting in towns, only the males are used because the fruit from female plants has a nauseous smell. The fruit contains butanoic acid, it has the aroma of rancid butter[200]. Ginkgo is a very ornamental plant[1, 117] and there are several named forms[11, 200]. This species is the only surviving member of a family that was believed to be extinct until fairly recent times. It has probably remained virtually unchanged for at least 150 million years and might have been growing when the dinosaurs were roaming the earth[237]. It is exceptional in having motile sperm[185] and fertilization may not take place until after the seed has fallen from the tree[81]. This genus belongs to a very ancient order and has affinities with tree ferns and cycads[185]. The ginkgo is usually slow growing, averaging less than 30cm per year with growth taking place from late May to the end of August[185]. Growth is also unpredictable, in some years trees may not put on any new growth whilst in others there may be 1 metre of growth[185]. This variability does not seem to be connected to water or nutrient availability. Trees are probably long-lived in Britain, one of the original plantings (in 1758) is still growing and healthy at Kew (1993). Plants are not troubled by insects or diseases[132, 200], have they evolved a resistance?[132]. Ginkgo is a popular food and medicinal crop in China, the plants are often cultivated for this purpose and are commonly grown in and around temples. Plants are either male or female, one male plant can pollinate up to 5 females. It takes up to 35 years from seed for plants to come into bearing[117]. Prior to maturity the sexes can often be distinguished because female plants tend to have almost horizontal branches and deeply incised leaves whilst males have branches at a sharper angle to the trunk and their leaves are not so deeply lobed[132]. Branches of male trees can be grafted onto female frees in order to fertilize them. When a branch from a female plant was grafted onto a male plant at Kew it fruited prolifically[11]. Female trees have often been seen in various gardens with good crops of fruit[K]. Seeds are marked by two or three longitudinal ridges, it is said that those with two ridges produce female plants whilst those with three ridges produce male plants[178]. Trees can be coppiced[200]. They can also be pruned into a fan-shape for growing on walls[202]. Another report says that the trees dislike pruning and will often die back as a result[238].
Propagation
Seed - best sown as soon as it is ripe in a cold frame or in a sheltered outdoor bed[78, 80]. The seed requires stratification according to one report[78] whilst another says that stratification is not required[80] and that the seed can be sown in spring but that it must not have been allowed to dry out[80]. Germination is usually good to fair. Prick out the seedlings into individual pots when they are large enough to handle and grow them on in light shade in the greenhouse for their first year. Plant them out into their permanent positions in the following spring[78, 80] and consider giving them some protection from winter cold for their first winter outdoors[K]. Softwood cuttings in a frame in spring[238]. Cuttings of half-ripe wood, July/August in a frame. The cutting may not grow away in its first year but usually grows all right after that[113]. Cuttings of mature wood, December in a frame[200].
Pests and diseases
Varieties
- 'Fastigiata' - A very upright female form, it produces good crops of seeds when in the company of a male, though the seed is a bit smaller than the species[K].
- 'King of Dongting' - A female form, despite its name. This form is widely grown in China for its seed.
Gallery
Ginkgo seeds and leaves
Ginkgo mature seeds and autumn leaf colour
A closeup of a Ginkgo leaf
autumn leaves and seeds
Female gametophyte, dissected from a seed freshly shed from the tree, containing a well-developed embryo
Fossil Ginkgo leaves from the Jurassic of England
Ginkgo adiantoides Eocene fossil leaf from the Tranquille Shale of British Columbia, Canada.
Ginkgos along Harlem Avenue in Riverside, Illinois
Ginkgo leaves painted on an asphalt walkway to guide tourists to a ginkgo forest in Dongducheon, South Korea.
In South Korea, Sungkyunkwan University's logo is a ginkgo leaf. Its main campus features several gingko trees that were planted in 1519 and still stand today.
Ginkgo tree in autumn
Ginkgo as penjing in the Montreal Botanical Garden]]
Ginkgo pollen cones
References
- ↑ Palaeobiology: The missing link in Ginkgo evolution, journal: Nature, volume 423, page 821
- ↑ http://www.ucmp.berkeley.edu/seedplants/ginkgoales/ginkgofr.html
- ↑ Ginkgoales: More on Morphology
- ↑ http://hort.ufl.edu/trees/GINBILB.pdf
- ↑ Michigan Gardener's Guide, ISBN 1930604203
- ↑ http://www.sustland.umn.edu/design/insect.htm
- Plants for a Future - source of some creative commons text
- Standard Cyclopedia of Horticulture, by L. H. Bailey, MacMillan Co., 1963
External links
- w:Ginkgo biloba. Some of the material on this page may be from Wikipedia, under the Creative Commons license.
- Ginkgo biloba QR Code (Size 50, 100, 200, 500)
