Clissold Park Redux #5: Hedera Hideaway
The cache, a small flip-topped plastic tube, is hidden on the northern edge of the park, at the location of a previous cache of mine GC5BMWK Clissold Park Revisited #2: Off-stump which was hidden on 25/8/14 and archived a year later (following repeated replacement and subsequent muggling) on 29/8 15 after some 62 finds.
I decided to try again with another cache at the location as the area still has no cache and the stump in question has since become festooned with the infamous cache protector and cachers' nightmare . . . ivy!
Fortunately, the hint should greatly reduce the challenge of finding the cache adjacent to a muggle-frequented path whilst the ivy can continue to provide good concealment and protection against those fiendish muggles!
Common or English ivy (Hedera helix helix) is one of 3 sub-species of 12-15 species of rampant, evergreen, clinging, ground-creeping, trailing or climbing vines in the ginseng family native to central, northern and western Europe.
It is a familiar sight in gardens, waste spaces, on house walls, tree trunks and in wild areas across its native habitat. On level ground it remains creeping, not exceeding 5–20 cm height, but on suitable surfaces for climbing, including trees, natural rock outcrops or man-made structures such as quarry rock faces or built masonry and wooden structures, it can climb to at least 30m above the ground. It climbs by means of aerial rootlets with matted pads which cling strongly to the substrate.
Despite the fact that it adheres to tree trunks, English ivy isn't a parasite. Only the roots attached to the ground penetrate to absorb nutrients. The function of the aerial roots is attachment to a support, not absorption.
Ivies have two leaf types, with palmately-lobed juvenile leaves on creeping and climbing stems and unlobed cordate adult leaves on fertile flowering stems exposed to full sun, usually high in the crowns of trees or the tops of rock faces, from 2 m or more above ground.
The juvenile and adult shoots also differ, the former being slender, flexible and scrambling or climbing with small aerial roots to affix the shoot to the substrate (rock or tree bark), the latter thicker, self-supporting and without roots.
The flowers are greenish-yellow with five small petals; they are produced in umbels in autumn to early winter and are very rich in nectar.
The fruit is a greenish-black, dark purple or (rarely) yellow berry 5–10 mm diameter with 1-5 seeds, 
ripening in late winter to mid-spring. The seeds are dispersed by birds which eat the berries.
The species differ in detail of the leaf shape and size (particularly of the juvenile leaves) and in the structure of the leaf trichomes, and also in the size and, to a lesser extent, the colour of the flowers and fruit.
Ivies are of major ecological importance for their nectar and fruit production, both produced at times of the year when few other nectar or fruit sources are available. The ivy bee Colletes hederae is completely dependent on ivy flowers, timing its entire life cycle around ivy flowering.
It is widely cultivated as an ornamental plant. Within its native range, the species is greatly valued for attracting wildlife. The flowers are visited by over 70 species of nectar-feeding insects, and the berries eaten by at least 16 bird species including thrushes, blackcaps, and woodpigeons. The foliage, which provides dense evergreen shelter, is eaten by the larvae of various species of butterflies and moths and is also browsed by deer.
In Europe, it is frequently planted to cover walls and the government recommends growing it on buildings for its ability to cool the interior in summer, while providing insulation in winter, as well as protecting the covered building from soil moisture, temperature fluctuations and direct exposure to heavy weather. Further uses include weed suppression in plantings, beautifying unsightly facades and providing additional green by growing on tree trunks. Numerous cultivars with variegated foliage and/or unusual leaf shapes have been selected for horticultural use.
However, it can be problematic. It is a fast-growing, self-clinging climber that is capable of causing damage to brickwork, guttering, etc. and hiding potentially serious structural faults, as well as harbouring unwelcome pests. Careful planning and placement are therefore essential
See here for more information on this fascinating plant.
Problems and dangers
On trees: There is much debate on whether or not ivy climbing trees will harm them. In Europe, the harm is generally minor although there can be competition for soil nutrients, light, and water, and senescent trees supporting heavy ivy growth are liable to windthrow damage.
Exotic Invasive: ivy only tends to be a nuisance where it is an introduced plant. In its native habitat, it's more likely to form a peaceful but assertive part of its environment.
Toxicity: The berries are moderately toxic. Ivy foliage contains triterpenoid saponins and falcarinol. Falcarinol may cause contact dermatitis - but also kills breast cancer cells.
Geocaching: Ivy is regarded as evil by many geocachers as its dense foliage and roots structure provide a very challenging environment in which to locate a cache - especially if the cache itself is small and/or also camouflaged. So it is hoped that - utilising the hint and provided it is replaced correctly in the required position - this cache will not be a source of much frustration and anguish but rather a pleasant encounter with this remarkable plant!
Symbolism, Traditions and Mythology
Although it is often admired for its beautiful appearance on the walls of buildings, in the past, it was valued for more than its appearance. It had important symbolic meanings and was part of a rich mythology. Even today, some people appreciate this symbolism.
See here for more information, including ivy's connections with Dionyus (or Bacchus) the Greek god of wine agriculture, festivity & theatre, Tristan & Isolde, Druids, weddings, Christmas carols & decorations, femininity, and US universities!
Ethnomedical uses
Ivy extracts are used in cough medicines. In the past, the leaves and berries were taken orally as an expectorant to treat cough and bronchitis. In 1597, the British herbalist John Gerard recommended water infused with ivy leaves as a wash for sore or watering eyes. The leaves can cause severe contact dermatitis in some people.
See here for a video of the Krautrock band One Sentence.Supervisor performing Hedera Helix.