Acanthus 'Summer Beauty'

The aim of this page, and it is probably an over ambitious one, is to gather together a collection of terms used in gardening/horticulture and explain what they mean and try to justify there use. The reason of attempting this is two fold. On the one hand it will I hope save me from repeatedly explaining the same words over again in the remainder of the site and on the other provide a general source of reference when the terms are come across elsewhere.

I have deliberately avoided using the word “complete” because lists of the sort can never be complete and some of the explanations may well contradict what you hear elsewhere. If that is the case all I can say in my defence is I will of course endeavour to check my explanations and many will be based on my profession training and experience.

Then again I am no more infallible than the next person and look forward to your feedback.

Sequestered Iron

When plants are grown in a soil which is to alkaline for them they suffer from iron deficiency as a result of the effect the pH has on the nutrients which are available to plants growing in it. Sequestered iron is iron in a form which is not affected by the pH and so it remains available to the plants. It is really only a short term measure so it has to be regularly reapplied to the plants.


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.

Soft Landscaping

This loose term is more frequently seen used within professional horticulture but simply means the soft things that grow ( i.e. plants) and the soil or compost they grow in. So it includes trees, shrubs, hardy perennials, grass, etc.. It generally doesn’t include vegetables grown purely for consumption, there are a number of very ornamental vegetable that would then be soft landscaping, as commercially a landscaper would not normally be involved in vegetable growing, just providing space for their cultivation in a garden. Commercially vegetable growing would be something undertaken by a market gardener which has nothing to do with landscaping.


What soil is should at first sight be pretty self evident but to a soil scientist, yes there is such a person (they study soil), soil is a very complex thing. The problem is we all tend to overlook soil; it’s that muddy stuff in the garden. It is though a complex and delicate ecosystem in its own right. The main parts are:

  • Soil water
  • Organic mater
  • Soil flora
  • Soil fauna
  • Mineral components
  • Soil air

Soil water

This is simply the water in the soil, but it is a very important and complex mixture of chemicals dissolved in water.


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.


This stands for the Sports Turf Research institute, though it now goes by the name STRI, which are based at Bingley in West Yorkshire. It was established in 1929 by the golf clubs to provide them with a research and advice service. By 1950 it had established itself an enviable reputation and had extended it remit to all managed sports turf. Though its area of expertise is in the care and management of professional sports pitches there is an active exchange of views with people like the RHS.


This is a layer of crushed stone used under paving to form, in effect, a stable foundation for it and is found between the bedding course and the subgrade. It is made of stone which has been crushed and sieved stone to end up with a mixture of sizes from  normally about 40 mm down to dust. The proportions of the different sizes should be such that the smaller stones bind the larger ones together to stop them moving and these are bound together by the smaller onesl. The source of the stone varies widely according to what is the cheapest local supply and includes limestone, dolomite, and waste concrete and waste tarmac. It goes by various names; dolly, dolomite, crusher run, type 1, MOT type 1, road plannings, 40mm down  and many others. Ministry of transport type 1 is a type of subbase produced to stringent standards which while making it perfectly suitable for garden use it is a degree of over engineering. There is also type 2 and when I asked a technician at a quarry the difference compared to type 1 he just said “very little”!

 Dolomite has the disadvantage that it becomes saturated with water when you attempt to compact it there is a tendency for it to turn to something resembling plasticine in texture, although it hardens on drying out and road planning tend to become greasy when wet. Only hard stone should be used as even the hardest sandstone, for example, will rapidly breakdown to sand in use. Once spread subbase should be compacted with either a vibrating roller or plate BUT do not attempt to compact more than a 150mm deep layer at any one time.


(plural taxa) is the individual levels of taxonomic rank. E.g. genus is one taxon and  species is a second taxon.

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


























(The principal taxa or in bold)

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