Hypocreopsis rhododendri, or hazel gloves is a fungi which grows in temperate rainforest. It is nationally scarce and is a UK Biodiversity Action Plan priority fungi species. It is parasitic on Hymenochaete corrugata or glue crust fungi, which is a fascinating fungi in it’s own right. It glues dead twigs and branches to each other and to live twigs and branches. This allows it to pass from one tree to another through the canopy and allows it to colonise the dead wood without competition from all the other fungi which inhabit the forest floor. Glue crust fungi starts the process of glueing two pieces of wood together with yellow tufts which emerge from the infected wood. If these touch a twig or branch, they will start bonding the two together. The air needs to remain humid throughout the process, to prevent the tufts becoming dessicated.
As the name suggests, hazel gloves is mainly found on hazel, but it is also regularly found on blackthorn and has also been found on willow. In America it grows on rhododendron, but it has not been found growing on rhododendron in the UK.
The “gloves” part of the name “hazel gloves” refers to the form of the ascomata, the part of the fungi which is visible to the human eye, where the fruiting bodies grow. This ascomata looks like fingers comprised of a lichen-like substance. The fruiting bodies are small black dots on the ascomata. The very similar willow gloves has the Latin name Hypocreopsis lichenoides, due to its lichen-like appearance. Hypocreopsis lichenoides is thought to be extinct in England.
When we survey woodlands, we map hazel gloves fungi and glue crust fungi. Mapping the glue crust fungi allows us to look for hazel gloves if we’re surveying the woodland later. If we find hazel gloves, this effects our management recommendations for the woodland.
During a survey of a particularly wet woodland, even by temperate rainforest standards, we came across some growing on hawthorn and a conifer that we believe to be western red cedar. It is hard to be sure if it is western red cedar because it’s in such poor health. We sent a sample off to Kew and Dr Paul Cannon, who is a taxonomical mycologist he confirmed that the fungi is Hypocreopsis rhododendri and the stem it was on was consistent with western red cedar. He said it was the only example of hazel gloves on a conifer outside of China. This shows how much there is to learn about this species. It also makes it more important to preserve the examples of the species that exist. We’ve also sent a sample to Daisy Yiangou, who’s a research student at Cardiff University. We’re looking forward to seeing what she finds.
Conservation Requirements
High humidity is required for glue crust and hazel gloves. To maintain high humidity:
- Avoid draining land and consider rewetting.
- Avoid removing surrounding trees and shrubs where this will increase drying winds.
- Avoid removing too much tree cover over Hazel, Blackthorn or other host trees and shrubs, where this will put them in full sun.
Abundant deadwood on hazel is required. To maintain abundant deadwood:
- Consider fencing cattle away from hazel where they will damage stools.
- Avoid cutting hazel back, or reinstating coppice where hazel gloves or glue crust fungi are present.
A continuation of hazel or blackthorn canopy is required to allow glue crust fungi to colonise new deadwood.
- Avoid removing or coppicing hazel not showing signs of glue crust fungi or hazel gloves, where this might isolate areas of hazel in suitable habitat.
- Bear in mind that absence of visible signs of the fungi doesn’t mean that the fungi is absent. Where some glue crust or hazel gloves exists on a site, all hazel and blackthorn should be treated as a potential host.
- Remove high canopy trees where excessive shading is likely to endanger hazel or blackthorn scrub. Favour a canopy of lightly shading trees, such as oak and ash, rather than heavily shading trees such as beech and sycamore.
- Consider controlling deer, where they are affecting regeneration of hazel.
- Consider controlling grey squirrels.
Useful Links
A report on hazel gloves by Natural England (2003). This is a bit out of date, but is useful.
https://publications.naturalengland.org.uk/publication/128007
A survey of hazel gloves sites in 2016 in Mid Argyll. Interesting reading.
https://www.nature.scot/sites/default/files/Publication%202016%20-%20SNH%20Commissioned%20Report%20877%20-%20Hazel%20gloves%20fungus%20%28Hypocreopsis%20rhododendri%29%20survey%20of%20mid%20Argyll.pdf
Some basic information from the Woodland Trust.
https://www.woodlandtrust.org.uk/trees-woods-and-wildlife/fungi-and-lichens/hazel-gloves-fungus
A factsheet from The Sylva Foundation containing information about habitat requirements.
https://woodlandwildlifetoolkit.sylva.org.uk/factsheet/142/Hazel+Gloves