Tough and fascinating plants

Taxodium
Taxodium
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I imagine the Christmas tree has been put to bed for another year, but many of the conifers in our gardens continue to remain a feature.

We have been doing some conifer identification tests at Manea School of Gardening – tests which require very close attention to detail.

Once you can tell a Picea (often called a spruce) from a Pinus, or pine, you really notice these unique plants and learn to appreciate them as more than just ‘the conifer over there.’ However, there are a couple of things I want to set straight: firstly, not all conifers are evergreen. The redwoods, such as Metasequoia glyptostroboides, are deciduous and drop their leaves over winter.

However, they are in the conifer category as they’re classed as a gymnosperm – a plant which produces naked seed, with no true fruit or seed pod. All our conifers are gymnosperms and they are adapted to harsh cold or windy conditions, the redwood being no exception.

Conifers are far from the only reliable evergreen trees and must not be seen as the ‘go to’ for any spot in need of an evergreen tree or shrub. Not least because some can shoot up a couple of extra metres before you realise!

Recently, the RHS students at MSoG visited the Cambridge University Botanic Gardens where there was a huge array of conifers on display. One particularly interesting tree was the Taxodium distichum, sometimes known as the swamp cypress, which is capable of growing very close to, or in, water.

It has developed a handy strategy to cope with having its roots submerged in water: it has pneumatophores. These have the appearance of knobbly knees clustered around the trunk and it is thought that they contribute a supply of oxygen to the roots and help stabilise the plant in potentially poor soil.

In complete contrast to the typical image we have of a conifer such as Leylandii, are two of my favourites, the Ginkgo biloba (commonly known as maidenhair, it has a fanned leaf) and the monkey puzzle tree – Araucaria araucana. Monkey puzzles are incredibly prickly and have distinctive branches which appear slightly fuzzy from a distance. However, what will often appear an innocent potted plant can belt up to 6m in a lot less time than many people imagine and controlling them is difficult; we have to remember that pruning is not natural!

Apart from wind damage and herbivores eating lower branches, plants do not expect pruning and monkey puzzles, like many conifers, do not respond well to a harsh prune.

Evergreen conifers, particularly, do not store nutrients and goodness as the leaves photosynthesise continually – so, aside from some of the Thuja conifers, they may not thank you for a harsh prune and will not tend to regrow from old wood. By contrast, now is generally a good time to prune a deciduous tree as the goodness has been taken down into the trunk and main branches, ready to erupt in spring and form a neat shape from where you have pruned. You can also get round to it before the birds start nesting!

Love them or hate them, conifers are a tough and fascinating bunch of plants.

- Manea School of Gardening (RHS Approved Centre)

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