Cornus controversa

Cornus controversa 'Variegata'
Cornus controversa ‘Variegata’

Best known in gardens in the form of Cornus controversa ‘Variegata’ this plant has had a convoluted history. The species C. controversa Heml. was first “discovered” in cultivation. In January of 1909 an article was published in Curtis’s Botanical Magazine which discussed the naming of Cornus macrophylla and the authors noted that there appeared to be confusion regarding the name. Though introduced back in 1827 it was not widely grown but it was known to be a tall and bushy plant when observed in the wild and this varied little over it wide natural range.  William Botting Hemley who had retired as Keeper of the Herbarium and Library at Kew the year before had studied this and noted that the examples in cultivation were a mixture of two species: one with opposite leaves and the other alternate.

Cornus controversa 'Variegata' foliage
Cornus controversa ‘Variegata’ foliage

The simple fact was that the naming had got into a mess but when the original specimen that Wallich had named C. macrophylla was checked it had opposite leaves and the original description in Flora indica of 1820 described the leaves as “sub-opposite”. Next Meyer in 1845 had also described the plant in a Saint Petersburg publication but naming it C. brachypoda. All this resulted in America and continental Europe using Meyer’s name of C. brachypoda for the form of the plant with opposite leaves and C. macrophylla for the alternate leafed form while in Britain both forms were known as C. macrophylla. In an attempt to clear things up the German botanist Bernhard Koehne tried to split the species in the belief that the Himalayan form was a distinct species which he called C. corynostylis but got confused between the opposite and alternate leaf arrangements. To clear up this confusion William Hemley proposed that if the plant had its leaves arranged opposite one another on the branches it should be called C. macrophylla Wall. as has been Nathaniel Wallich’s intention and the alternate leafed form should be a separate species Cornus controversa Hemsl. meaning cornus controversial, a most appropriate name. And that is as it has remained; apart from an attempt to place several of the cornus species, this one included, in the genus Swida in the 1960’s.

Cornus controversa 'Variegata' foliage close up
Cornus controversa ‘Variegata’ foliage close up

That would be the end of it with C. controversa Hemsl. providing us with a very garden worthy small tree with tiered branches and masses of cream flowers in May, but towards the end of the 19th century a variegated from was found and shortly before 1890 Veitch Nurseries introduced it as Cornus brachypoda ‘Variegata’. Now known as Cornus controversa ‘Variegata’ this is a plant which stands out to gardeners and non-gardeners alike. Smaller growing than the original but retaining the tier arrangement of branches, the leaves are longer and narrower and tend to be asymmetrical in shape with an irregular creamy-white margin. Known by the common name The Wedding Cake Tree its hardy in the UK and was awarded an AMG by the RHS in 1993.

Its size and shape means it is best suited to a larger garden where it has room to grow and show off its tiered habit and would look particularly effective in a large border with an under planting of spring bulbs. The flowers are followed by berries and on some soils attractive autumn foliage. The plant is often produced by grafting and so care should be taken to watch out for suckers from the more vigorous rootstock which need to be removed as soon as seen.

Viscum album

Viscum album
Viscum album subsp. platyspermum on limes trees at Hampton Court Palace, London

Mistletoe has fascinated humans for millennium, many plants have superstitions attached to them but mistletoe seems to have attracted more than most. It’s not hard to understand that a clump of evergreen leaves growing out of dormant tree in midwinter would grab the imagination. The druids are said to particularly venerate mistletoe growing on an oak tree, something it rarely does, harvesting it with a golden scythe on the 6th day after a new moon. Consisting that the plant is woody and gold is an extremely soft metal I not sure how true that is and as they left no written records of themselves this could just be dramatic invention. It still plays an important part in culture with the tradition of kissing under the mistletoe at Christmas but the plant is poisonous with a few berries bring on stomach ache though serious poisoning is rare.

Viscum album is wide spread across Europe and it has over the centuries been seen as a cure of a vast range of ailments right up to the present time. Diokorides (the 1st century AD Greek physician) reported that Hippocrates (in the 4th to 5th century BC) believed mistletoe could be used in the treatment of complaints the spleen and menstruation. Over the following centuries it has been recommended as a treatment for swellings, tumours, epilepsy, infertility and ulcers. In more recent times people have tried to use is to treat hypertension and cancer.

Viscum album
Viscum album (Mistletoe)

The genus Viscum L. contains about 100 spices but only V. album L. is native the UK and then mainly in the south and midlands. In naming Viscum album L.. Linnaeus took the Latin for mistletoe as the genus and album, no doubt referring to the distinct white berries, for the species name and listed it in volume 2 of his Species Plantarum. The genus Viscum L. is presently in the family Santalaceae along with 6 other genera. The common name Mistletoe comes from the old English mistel and many semi-parasitic plants around the world have the same common name. It is also known as including All-heal and Masslin in England and has many other names across Europe, Germany having a particularly large collection of names for it.

Mistletoe is notoriously difficult to establish and the species is now divided into 3 sub-species depending on the host plant it lives on.

Viscum album subsp. abietis (Wiesb.) Abrom. which grows on Abies species.

Viscum album subsp. austriacum (Wiesb.) Vollm. which grows on pine trees and very rarely on spruce.

Viscum album subsp. platyspermum Kell. (subsp. album) which grows on hard wood trees.

This goes in part towards explaining why it is so difficult to establish mistletoe as the sub-species are very specific to their chosen host but there also appears to be genetic factors as not all potential host can be infected with equal ease. For example, oak is rarely infected but even then there is a wide range of how readily a plant will be infected with a particular oak species. Therefore, where a plant has only a few mistletoe plants on it not become host to a lot and only specimens with a lot of mistletoes will host a lot.

Mistletoe is evergreen with tiny flowers that are insect pollinated and would never be noticed; the insects are attracted by the sweet smell . The male and female flowers are on separate plants with about 4 times as many female plants as male ones. The plants flower between the end of February and April  and the fruits (or berries) appear from October to May with Mid-March to mid-May being the best time to sow the seed, making sure to brake the outer coating and allowing the sticky contents to help the seed adhere to the bark of the host tree.

Mistletoe is a parasite, all be it a partial one, taking water and minerals from the host tree and this weakens the tree. Infected apples trees will yield between 7% and 56% less depending on how vigorous the rootstock is, with the plants growing on the more vigorous rootstocks affected the least. Once established the Mistletoe shoot doesn’t divide for the first 3 or 4 years then each year the shoot divides in two, ultimately reaching about 1 metre across, so giving a very rough and ready guide to its age.

 

Taxonomic rank

This relates to the level within the hierarchy of plant names. The series of taxa for botany are set out in the International Code of Nomenclature for algae, fungi, and plants. Not all plants have an entry for every taxa and above the level of genus there is often a great degree of disagreement as to what belongs where. The important thing is that any plant can be identified by its genus and below.

 

Taxonomic rank

Kingdom

Subkingdom

Division

Subdivision

Class

Subclass

Superorder

Order

Suborder

Family

Subfamily

Tribe

Subtribe

Genus

Subgenus

Section

Subsection

Series

Subseries

Species

Subspecies

Variety

Subvariety

Form

Subform

(The principal taxa or in bold)

Botany for Gardeners by Brian Capon

The danger with this book is that is title may well put off many potential readers. The vast majority of gardeners do not see themselves as botanist: but spending hours studying the plants they grow, can’t grow and aspire to grow. As a gardener you consider the plants shape, colour, needs development and reproduction; yet little thought is given to the science under pinning these characteristics. All too often the science bit it shied away from as being too difficult or not relevant; more likely than not because we were put of the subject at school. The thing is gardening is to a large part applied botany and to deny it is not only short sighted but also making life harder. The problem is at first botany can be off putting in its apparent complexity and little is available in the way of bridging this gap. Brian Capon has set out to do just that with this book.

A professional botanist by training and a gardener by inclination, he has set out to provide a means of introducing gardeners to the how and why of plants. In doing so he has created a book that fills a real gap in gardening literature.

His years teaching botany, often to non-botanists, has given him a natural ability to do mystify his subject. Like all good teachers he has a natural gift for bring his subject to life and sharing his enthusiasm. The different aspects of the subject are approached in a logical order and the book is kept sufficiently concise so that it dose not intimidate those new to the field. It is well illustrated with photographs, line drawings and examples to add understanding. Though no part of the book can go into great depth, doing so would be counter productive, it ends with a list of further reading to encourage the reader to delve further into the subject.

Hopefully the present upsurge in interest in science will encourage gardeners to set aside there feat of it and temp them into learning a little bit more about the plants they grow. The book will not necessarily make them botanist; but it will make them better gardeners.

The Cambridge Illustrated Glossary of Botanical Terms by Michael Hickey and Clive King

This may not seem an obvious choice to include in this list and retailing at about £38 for a paperback it is not exactly cheap; but it does plug a very important gap. This book provides an accessible explanation of the often confusing technical terms used to describe plants. These are words used in botanical and horticultural books and other literature to describe plants and their characteristics. Their use causes considerable confusion and, sadly, puts off many; but are vital to help describe plants in an unambiguous way. The result is that many plant descriptions rely on words which make no sense to most people or very specific uses of words with much broader colloquial means. Frustrating as this is the accurate naming and description of plants would be impossible without them; as they allow the necessary degree of precision when trying to describe the difference between plants.

To achieve this, the book is divided into two sections; the first provides a list of words with a brief explanation of the meaning and cross references to the appropriate illustration in the second section. This second section justifies the large size of the book: being A4 in size. This is a selection of clear black and white line drawings illustrating the many terms. Most books attempting to describe this with illustrations rely on photographs, but such a technique could never achieve the clarity that these accomplish.

While of limited use to many people, and hence the publishers high price, anyone serious about understanding plants and there descriptions would do well to get hold of a copy. This is not the sort of book you are going to sit and read it is one you are going to find you are repeatedly pulling down of your shelves to refer to.