I will take Rhododendron nuttallii any time

I was looking at a newly released NZ gardening book and happened upon praise for a fruit described as a Chilean guava. For decades, the term Chilean guava, sometimes strawberry guava, has been widely known in this country to refer to a South American fruit called Psidium littorale. It is a biggish, evergreen shrub which produces fruit about the size of a large marble or a gobstopper in red or yellow with rather large pips. It is at least the same genus as the tropical guava – the pink fruit that most of us know in tins from South Africa.

Enter Myrtus ugni (or Ugni molinae to be more correct), usually called the New Zealand cranberry (to which it is entirely unrelated). In Australia, it is known as the Tazzieberry but internationally it is often referred to as the Chilean guava. In recent times there has been a growing tendency in the nursery and retail trade (and now in publishing) to adopt the international common name and to refer to the New Zealand cranberry (aka Myrtus ugni) as the Chilean guava. No matter that there is a pre-exisiting fruiting bush widely known as that. In the aforementioned book, the only reason I knew the author was writing about Myrtus ugni and not Psidium littorale was by the picture. That is because the header was: “Chilean guava” with no botanical name given at all. Sometimes writers and publishers can dumb stuff down so far that they almost guarantee failure.

Two entirely different plants, both commonly called the Chilean guava

Common names can be helpful in gardening where proper names are often in Latin and hard to remember, but they are only helpful when there is shared understanding about the plant being so labelled. There is no excuse for not putting the proper name in smaller type beneath the common name in books, or indeed for failing to give alternative common names that are in wide usage.

What novice gardeners need is not the complete dumbing down of information to a jazzy but relatively useless level. They need skilled interpretation so that the wealth of information is sorted for them and they are gently encouraged to lift both their knowledge and skills level. Part of that is learning about plant names and plant families.
Why does it matter whether you understand these things? Think of cooking. You can make a perfectly acceptable cheese sauce using any old cheddar but to lift your cooking to a higher level, it is usually necessary to understand the different types of cheeses and just when Parmesan is going to give a better result than Mozzarella or even Pecorino.

You can enjoy your garden and fill it with seeds and cuttings without knowing the names of any of them, let alone where they come from or to which plant family they belong. You may even be perfectly happy growing one Chilean guava while thinking it is the other Chilean guava you have. But it becomes a great deal more interesting when you know more. And the more you know, the more likely your outcomes will be successful and the better your garden will be.

It was an eighteenth century Swedish botanist, Carl Linnaeus, who reorganized the structure of living things, including plants, into the order or sequence (called taxonomy) that we still adhere to today. You can get by quite satisfactorily just understanding the end points of species and genus.

The species is specific to one plant, though there can be some variation within a species – think of brothers and sisters. So if you take the gorgeous Rhododendron nuttallii (and it is so gorgeous, I will take it any time), the nuttallii is the species. There are differences between various forms of nuttalliis but botanically they all very close. The rhododendron part of the name is the genera and there are many different species within that genera – in fact all the different rhododendron, vireya and azalea species. They are like the cousins, second cousins and third cousins plus assorted relatives.

Plant names are in two parts: first the genus and then the species. Hence Rhododendron nuttallii. Even the humble common garden bean has a two part name – Phaesolus vulgaris for most green beans and Phaesolus coccineus for runner beans. Runner beans are a different species to green beans but take it a step up and they are the same genus. The naming of plants in this form is one of Linnaeus’ most enduring legacies. Prior to that, the naming of plants was entirely random and told you nothing at all about the botany of the plant (which is a bit of a problem when it involves medicinal herbs). It was also a source of considerable confusion and duplication.

Linnaeus’s system of classifying plant species through names (called binomial – two names) has stood the test of time over nearly 300 years. But apparently in this country, it is too difficult for us to grasp. If the trends of the past decade are anything to go by, we must return to the pre-Linnaeus era because we are only capable of managing common names, no matter that it can cause confusion. It is apparently asking too much that the botanical name be run alongside the common name.

First published in the Waikato Times and reproduced here with their permission.