Olearia x macrodonta

Olearia macrodonta bush
Olearia macrodonta

The “New Zealand Holly” rightly earns is common name; its pointy edged leaves make look a lot like a grey holly leaf. They can be a little tender but are sufficiently tolerant of salt laden winds that that do well near the coast. This makes them a valuable plant in seaside gardens where their tolerance of salt and the relative absence of hard frosts makes them well suited. In all but the most exposed gardens they can be grown; coming through all but the worst winters with little or no damage. They are very wide spread in North West Scotland, to the point of almost being naturalised.

Olearia macrodonta bark
Olearia macrodonta bark

While evergreen like holly; the leaves are not as hard and vicious as holly (as anyone who has hand weeded around a holly bush will testify too). It also differs from Holly in that it grows quickly; forming a medium sized bush, and given time a small tree. Holly on the other hand is rather slow growing.

In summer the New Zealand Holly is covered by mounds of white flowers and older specimens develop a peeling, almost shaggy, bark which new growths breaks away freely.

Close up of Picture of an Olearia macrodonta shoot
Olearia macrodonta shoot

As the common name suggests it is a plant native to New Zealand and was first described by Joseph Dalton Hooker who in 1864 named it Eurybia dentata var. oblongifolia. This turned out to be incorrect and in 1884 John Gilbert Baker, working at Kew under Hooker, renamed it Olearia macrodonata. Though this is the name it is normally grown under in the UK; the New Zealand government’s own data base lists it as Olearia ×macrodonta Baker a hybrid between two species: O. ilicifolia and O. arborescens.

Though Olearia ×macrodonta is widely grow in the UK, the dwarf form Olearia macrodonta ‘Minor’ would be well worth seeking out for a court yard garden or rockery. This plant looks like a miniature version of the original, being smaller in all its parts, and it is listed in the RHS Plant Finder.

Olearia macrodonta 'Minor'
Olearia macrodonta ‘Minor’

 

Species

The species is the basic unit that we divide living things into and originally species were seen as clearly distinct from one another. What puzzled scientist was how species appeared in the first place? The answer was species evolved from other species as a result of a battle for survival; as carefully argued in Charles Darwin’s “On the Origin of Species by Means of natural Selection or, The Preservation of Favoured Races in the Struggle for Life”. As is often the case the answer to this question produced a second question; if species appear as the result of a gradual change from one species into a second, where does one species stop and the next start. This argument will keep taxonomist in work so long as there are species to classify!

Clearly this makes a precise definition of what a species is impossible and whether a plant belongs in a separate species to another is the result of a consensus being formed. This consensus though is not fixed and has to be open to debate.

Species is also the basic unit of plant and animal scientific names and the name of a species is the combination of both the genus and species names. The rules for how a species name is structured is defined by International Code of Nomenclature for algae, fungi, and plants (as it is now known) and this goes into great details; but some of the important rules are:

  • With in any genus no two species can have the same name or one that could cause confusion with others.
  • For plants; the species name cannot be the same as the genus it belongs in, unlike animal names. So Rattus rattus, the black rat, is a valid name for an animal but the style would be unacceptable for a plant.
  • Importantly the species is always begun with a lower case letter,
  • The genus should be written immediately before it (the genus can be abbreviated to its first letter if it does not risk causing confusion) and both the genus and species should be in italics or if not practical underlined.

Genus

This is a collection of very similar species and forms the first part of a plant’s scientific name. For example Alchemilla in Alchemilla Mollis and as such it is very important in the naming of plants. Ideally it would be best to have a clear definition as to what constitutes a genus and the International Code of Nomenclature for algae, fungi, and plants goes into great detail as to how a genus should be named. It does not though make any attempt to nail down what actually constitutes a genus and for a very good reason – you can’t. In practice it would be impossible, plants evolve into genera in what ever way evolution takes them and only much later to people come along and try to group them into genera, species, etc. In the end a genus is a collection one or more species which a consensus has been arrived at that they should be placed together because of there botanical similarities.

Crataegus monogyna

Crataegus monogyna
Crataegus monogyna – Hawthorn hedging

The common hedgerow plant Hawthorn is a familiar sight all over the UK and gets it name from it’s fruit which have the common name Haws and is sharp thorns. Also known as May or Mayflower due to its flowering time, it also goes by the common Quickthorn and Maythorn. Correctly known as Crataegus monogyna Jacq. It was placed in the genus Crataegus, created by Linneus, by Nikolaus Joseph von Jacquin (1727–1817) and first published in his 1775 flora of Austria.

Crataegus monogyna flowers
Crataegus monogyna flower

Its fragrant white flowers are one of the heralds of spring; their being borne with the leaves makes it easy to distinguish at a distance from Blackthorn, Prunus spinosus, as that flowers earlier and before its leaves have opened. Its reliable stocky growth and mass of intertwining braches covered in sharp thorns has made it the commonest hedging plant in the countryside. Historically it was laid to form hedges where its upright branches were cut nearly through, bent over and interwoven but these labour intensive skills are now little seen and it is cut with a variety of mechanical methods, all of which it happily tolerates. It is in fact very tolerant of being cut, and if can be cut flush with the ground it will still re-grow.

Crataegus monogyna leaves
Crataegus monogyna leaves

Its widespread occurrence can lead to related plants being misnamed C. monogyna and in fact globally Crataegus L. is a very large genus containing its being estimated something like 200 species. In practice the most likely plant to be confused with C. monogyna is Crataegus laevigata (Poiret) DC., known as the Midland Hawthorn or Two-styled Hawthorn, and the red flowered form Crataegus laevigata ‘Paul’s Scarlet’ is widely planted. Its main difference is that the leaves are not as deeply lobed as C. Monogyna but if you careful examine the flowers you will also see that C. monogyna generally has only one female style where as C. laevigata generally has two; hence the repective names monogyna and two-styled. In most garden settings it’s probably safe to assume if it’s a white flowered hawthorn its C. monogyna and if red then Crataegus laevigata‘Paul’s Scarlet’

Crataegus laevigata 'Paul's-Scarlet' flowers
Crataegus laevigata ‘Paul’s-Scarlet’ flowers

 

 

Variety

This is classification of plants below the level of species which share common characteristics but would freely interbreed with other varieties of the same species if the opportunity arose. For this reason different varieties are often separated geographically. When writing the name of a plant the variety name is written in italics or underlined, is immediately preceded by var. in normal type and this follows the species name. There tends to be a lot of confusion between variety and cultivar but the former only relates to plants which originate in the wild and the latter to plants which originate in cultivation.

Cultivar

This is a plant which has been selected in cultivation because of specific characteristics it shows which separate it from its wild origins and other cultivars. The rules regarding what is a cultivar, how it is named and how the word is used are laid down in the International Code of Nomenclature for Cultivated Plants. Only plants which are not found in the wild can be called cultivars and to show that they are the cultivar name is written in normal upright letters and enclosed in single quotation marks.

Botanical Latin

Botanist quickly found Latin lacked words they needed to describe the parts of a plant, the Romans having never seen any need to do such things, so they modified the language for their own needs. The school Latin you may have learnt  has evolved considerably since the Romans; to the point a Roman would hardly recognise it. This has lead to Botanical Latin, which has branched off from ‘School Latin’, and has developed its own means for words and grammar. Anyone wanting to learn more would do well to look at Botanical Latin by William T. Stearns which is the standard text on the subject. Its very heavy going though!

So how is a plant name constructed?

A diagram of a simple plant name
A Simple Plant Name

A basic plant name consist of a genus which starts with a capital letter and a species which does not both of which should be written in italic or underlined. This is to make it clear you are looking at a proper plant name. Good as this simple system is, and if that was it live would be a lot easier, often this is not enough and other bits get added. The most common for gardeners is a cultivar name (abbreviated to cv.) and this particularly good form of a plant which has been selected e.g. Photinia ‘Red Robin’ is a particularly good form of Photinia x fraseri and the cultivar name is written in normal type but enclosed in single quote marks.

So what is a genus? This is where things get messy. There is no nice neat definition of what actually constitutes a genus or a species. There are to lengthy codes lying down what is or is not a valid name, the International Code of Botanical Nomenclature and the International Code of Nomenclature for Cultivated Plants, both at which carefully avoid any definition of what constitutes a genus or species. In practice its all down to what people can agree on is a genus or a species. Guess what botanists often don’t agree and this leads to plant names being changed as people argue is this a genus or a species in a genus and so on. This is turn leads to the frequent complain that ‘they keep changing the *@*!* name’. The real problem plant names assume that all plants are related by evolution and the names should demonstrate this. So a group of genera will be placed in a family all of which have a common ancestor they evolved from. But this common ancestor is now extinct and lost to us. It’s rather like trying to work out if your neighbour is related to you with out any historical documents to refer to relying on appearance alone!

 

What you need of course is some sort of definition to tie down a genus and in practical terms a genus is a group of closely related species. This can on occasions be a group of one, but then is generally believed that there were other members but they have died out and become extinct. Similarly what a species is not that well defined. Traditionally a species was said to a group of plants which could breed with one another but then two different species could not be successfully crossed. This has a problem as gardens, and to a lesser extent the wild, are littered with plants which are the result of two species being crosses. Not to mention the number of plants which are the result of different genera being crossed! Really a species is a group of very similar plants, more similar that those included in the same genus, which look the same but are not genetically identical.

How many a dispute could have been deflated into a single paragraph if the disputants had dared to define their terms.
Aristotle
Greek critic, philosopher, physicist, & zoologist (384 BC – 322 BC)

Introducing plant names

I should really start off by saying something about plant names, as this is a real bugbear amongst gardeners. I thing just about everyone who has worked professionally in horticulture has been asked, generally in a tone of exasperation, why do we insist on using these weird names in a language of a people how died out centuries ago. This usually is answered by some mumblings about it avoiding different countries arguing about which language to use. This is actually more the reason the system is retained, along with the impracticality of changing it now! The real answer is far more complex, goes back at least to the conversion of Rome to Christianity and wends its way via the middle ages roman catholic church, Charlemagne and the use of Latin to control access to knowledge. That story is too long to delve into but by the time Carl Linnaeus set about creating his system of naming if he was to be taken seriously as a man of learning, and he certainly did, then he had no choice but to use Latin.

Carl Linnaeus is the man credited, some might even use the word blamed, with the naming system we use. In fact what may seem the two most obvious aspects, the use of Latin and using two words to name the plant, weren’t unique to his system having both been used in other attempts to place nature in a sense of order. His big idea was that the name didn’t physically describe the plant, it was just a label. The name John Smith only tells you that person is called John Smith and he has close relatives who last have the surname Smith. It does not tell you if he has dark or fair hair, or if he is tall or short. Try to give some one a name which describes them would be unworkable and so it proved with plant names. Therefore Garrya elliptica in itself tells you that the plant is related to other plants called Garrya and that is about it.