Garden Tool Set

Trunk of the Month: March 2015: Betula ermanii

Well, I can't believe it's March already! In this post, we'll investigate the trunk of Erman's birch, named after Georg Adolf Erman (1806-1877), a German physicist, who collected it from one of the species native homes, Kamchatka in North East Asia.

This species is sometimes also called the gold birch, which must be due to the vivid colouring of the bark. The genus Betula is well known for its peeling bark, often used in bushcraft as a tinder material when starting camp fires, due to the thin papery properties of the peel. In the photo above, it can be seen that the bark peels in shreds quite naturally, there is also a blistered layer of bark that has peeled but not broken from the rest of the bark in the middle.

This tree can reach a height up to 20 metres and spread to around 8 metres, but it will take up to 50 years to reach full size. It seems to be a popular horticultural tree and has been bred into a few cultivars, with 'Grayswood Hill' having the RHS Award of Garden Merit.

What I find most fascinating with this birch are the elongated lenticels that provide such a striking effect.

Every plant that generated secondary growth (wood) has lenticels, some herbaceous plants have them too. They are a product of the periderm that is the protective covering, replacing the epidermis, in parts of the plant that has secondary growth.

Lenticels are more important than they appear to be. This is because the inner tissues of stems and roots are metabolically active. Because of this, they need to exchange gases with the environment. Lenticels are the structures that allow the stems and roots to perform the essential gas exchange.

If a plant is left in water logged soil, it will drown because the lenticels cannot exchange gases with the soil. Apart from plants such as mangrove tree that send up structures known as pneumatophores. These aerial roots are covers with lenticels and allow the plant to breathe in the constantly changing environment in which it lives.

Interestingly, some fruits and vegetable also have lenticels. They can be seen as small dots on the surface, as in the apple and potato, below. These allow the apple and potato to continue respiring after harvesting - however they can also be an area of disease.

Lenticel rot can be a real problem, especially in potatoes where dry, sunken, discoloured lesions surround the lenticels. This is caused by a bacteria know as Pectobacterium carotovorum subsp. carotovorum and, depending on storage conditions, can lead to the whole tuber decaying.

Until next time - happy trunk hunting.

References:

Farrar, J., Nunez, J., & Davis, R. (2009). Losses due to lenticel rot are an increasing concern for Kern County potato growers California Agriculture, 63 (3), 127-130 DOI: 10.3733/ca.v063n03p127