Selective Weed killer

Also called a selective herbicide.

A weed killer that is more poisonous to some types of plants than others. Note that it selective weed killers are first weed killer, i.e. they kill all plants, and then the selective part is just how susceptible different plants are that particular chemical. Or to put it other way if you are not careful to make sure you follow the instructions accurately you will either kill off nothing or everything including the plants you what to keep.


The proper name for a weed killer. It’s formed from ‘herb’ meaning a plant (from the latin herba meaning a green plant) and ‘icide’ meaning it kills things. So you get insecticide, fungicide, biocide, pesticide, etc.


A plant, larger than a shrub, with a one or occasionally 2 or more clear stems which form a trunk(s). Above the trunk is a system of branches which gradually increase over the years.


A plant in the wrong place. That’s it really, any one plant can be or not be a weed depending where it’s growing, when it’s growing there and most of all who’s looking at it!

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.
Greek critic, philosopher, physicist, & zoologist (384 BC – 322 BC)

Alchemilla Mollis

Alchemills Mollis in flower
Alchemills Mollis

This is a very common garden plant, known as Lady’s Mantle, grown in many gardens for its attractive foliage and ability to provide a weed covering mat. It is easily grown in sun or light shade, only limited by heavy shade, in any normal garden soil; seeding itself freely about he garden give any opportunity. The lime green flowers could easily be over looked buts its charming habit of catching drops of dew or rain water in the folds of its leaves.

Alchemilla Mollis with water droplets on the leaves
Alchemilla Mollis with water droplets on the leaves

The plants grow to about 450 mm high and should be planted about 600 mm apart. As a hardy perennial the foliage dies down in autumn and cutting back the dead leaves in winter is all the care this plant requires. If it has not spread itself about the garden by self seeding, a tendency which can be controlled by removing the flowers once they start to die back, it can be propagated by division. The time of this division is not important with this easy plant.

Close up of Alchemilla mollis flowers
Close up of Alchemilla mollis flowers

The plant is quite distinctive in appearance and closes to it are probably the closely related Alchemilla erythropoda and A. alpina both of which are notably smaller. Alchemilla mollis is found naturalized in the wild in this country along with several other members of members of the genus some native, some naturalized. The genus Alchemilla is in the rose family and the pollen of many European member of the genus fails to fertilize the plants with the seed forming asexually.

Tackling the weeds

Yes you could dig them out with a garden fork, and you set out into the garden, fork in hand, and a heart full of spirit. About 10 minutes later some of the shine is going to start coming off the idea! Digging a garden is slow hard work, you only have 24 hours in your day and a lot of things you need to do. If this, and the VERY painful back injury you will soon be suffering from is not sufficient the following may well be. If the weeds are established you will have things like dandelions and docks with long tap roots which break off when you try and dig them out leaving the end of the root to re-grow. In addition, you will have couch and nettles with spreading roots which snap off when you dig them out leaving little pieces which re-grow. A 1 cm piece of couch root will still survive and flourish if buried 40 cm deep. I could go on listing weeds which will fight back when you start to dig them out but I’m sure you will have got the idea now.

So if we are going to get the garden tided up the most practical solution is to use a weed killer which will kill the perennial weeds.

When you go into the garden centre you will be faced with a bewildering array of garden chemicals but this is down more to the manufactures trying to sell their products more than the range of chemicals available. In fact there is a lot of concern within the horticultural industry that as the rules surrounding garden chemicals becomes stricter and stricter the range is rapidly shrinking to the point where there will be insufficient for the amateur gardener. That aside there is really only a choice of one product as you need something which will kill all the weeds effectively and then disappear so that it won’t poison what you are going to grow next. That is called glyphosate, so write the word down on a piece of paper and go out and pace out the size of your garden and write that down on the same piece of paper and ¦we’re off to the shops!


A plant with a system of woody stems which branch out and last from one year to the next gradually increasing in size. Ranges from prostate to several metres in height.

Hardy Perennial

These are plants with no woody stems lasting from one year to the next. Some have leaves which persist from one year to the next but by enlarge they die down to the ground at the end of each summer. Hardy perennial grow by spreading horizontally and tend to establish and flower quicker than trees and shrubs.

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.