Gardening with Gerry: the tree of life

The tree of life is remarkable for many reasons — it is a “living fossil”, an excellent ornamental tree, and it has medicinal properties. Ginkgo is derived from the Chinese name for the tree which translates as ‘silver fruit’.

The fruits start light green, turn yellow and when the skin is shed, the seeds are white. The ‘tree of life’ name comes from its incredible longevity, both as a fossil and as a living tree.

Ginkgo is so unique that it has to be classified by botanists not only in its own species, genus and family, but also in its own order, class and division. It is related only to plants that are fossils, species also ranked in the same lineage but are long gone.

There are other fossil trees, such as monkey puzzle, Wollemi pine and dawn redwood that date back to the days of the dinosaurs but they are not the unique survivors or they have modern relatives, but ginkgo stands alone.

Jurassic

Not only is it a fossil that dates back 270 million years to the Permian era, older than the Jurassic, but it is not thought to survive in the wild. It is considered that human intervention possibly hundreds of thousands of years ago has ensured its survival.

Cultivated at monasteries in China at least 1,000 years ago, some individual trees are claimed to be 2,500 years old. It has remarkable resistance to pests and diseases, seemingly having out-lasted all its troublemakers.

It also has the ability to produce new shoots and roots on old wood, a good quality for longevity, either for individual trees or a species. Mature trees can have several trunks as side growths shoot up and become established.

Ginkgo has been used in many countries around the world as a street tree, because it is hardy, endures wind well, tolerates pollution and resists insects and disease. It carries fine leaves, in a unique fan-shape, often split or partly split into two parts, or lobes, hence the Latin name ginkgo biloba. As a young tree, ginkgo grows fast and very upright, and this narrow shape is a benefit for a street tree, but it broadens as it ages.

Gingko makes a tree of generally about 10m but it is capable of much more and can reach 30m. In fact, some trees reputed to be of 50m exist in China. Thriving in areas of warm continental climate, it is very beautiful all year round, gaunt skeletal in winter, softly green in summer and pure butter yellow in autumn.

The trees are either male or female, but male trees are generally sought out and the females don’t seem to flower in our cooler climate. But in warm countries, the female trees drop soft fruit which smell strongly, not unlike rotten silage.

Health benefits

The nut-like seeds are eaten in China and Japan where they are regarded as having considerable health benefits. The extract of the leaves is used to enhance memory and a debate is continuing about its value in warding off dementia. It does seem to improve circulation and this can affect memory (as well as other aspects affected by circulation). However, it can have side-effects for those using blood-thinning drugs, and must be used only with a doctor’s advice.

Ginkgo is a fine tree for a rural garden. It can be grown in town gardens too but needs some space to look its best. It stands well near a house, making a fine contrast of foliage with the hardness of concrete or stone.

If you are looking for a truly remarkable specimen tree, this could be it. It thrives in any soil, acidic or limy, as long as it is reasonably good and does not get waterlogged or dried out in summer. It thrives by streams but it likes good drainage too. It grows faster in a warm spot, making it a sight to see in 15 or 20 years, and would only get better in the following thousand years… or so!

I keep finding vine weevil in my pots. Any advice? - Robert Burke, Athenry, Co Galway.

The black vine weevil (Otiorhynchus sulcatus) is an insect native to Europe but common in North America as well. It is a pest of many garden plants, primarily of pot plants, although plants growing in the ground can also be attacked. The adult weevil is matte black with fused wing covers, and is unable to fly.

A range of biological controls and chemicals have been used over many years. But the best control is to mix ordinary garden soil, riddled, half and half, with garden compost. The vine weevil larvae are prone to a wide range of natural enemies: eelworm, fungi, centipedes, ground beetles, among others. These are present in unsterilised garden soil, and not in peat compost.

Trees, shrubs and roses: Continue tree planting in good soil conditions. Roses can be tidied up in cold districts.

Flowers: Plant spring bulbs that were purchased, but not planted. Lift and divide perennial flowers.

Fruit, vegetables and herbs: Fruit trees and bushes can be planted if the ground is not heavy. Control weeds too.

Lawns: Try not to walk over lawn areas if the ground is wet after rain as it causes soil compaction.

Greenhouse and house plants: Check that the greenhouse frost protection heater is working. Water only plants that need it.