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The garden designer’s guide to specifying plants by Janine Pattison MSGD
The buyer of trees, shrubs and other plants has a wide range of options available when deciding what to select. There are literally thousands of varieties to choose from and the designer will spend a great deal of time deciding which plants are required for the new garden. Most designers are comfortable with using correct botanical plant names (as per the RHS Plant Finder) as this is a great assistance in avoiding misunderstandings when sourcing plants, but what is less understood is the need to be able to correctly specify the plants required.
The reason that correct plant specification is so important is that plants are available from nurseries and suppliers in a wide range of formats (various container sizes, heights and tree girths). All of these options will impact the immediate effect after planting and, of course, the cost. The more expensive plant will be substantially larger and this may be what the designer wants for instant effect.
For a designer to be confident they are ordering exactly what they want, they need to specify to the supplier their requirements in detail. This is also the only way that suppliers or nurseries can prepare accurate quotations for the supply of the plants required. An additional benefit is that these quotes can be compared on a ‘like-for-like’ basis, as all suppliers are quoting for the same material.
So, what requirements can be specified? The National Plant Specification details a range of characteristics that can be specified by the buyer. These vary for trees, shrubs, climbers, perennials, bulbs, hedging and fruit trees.
Trees
All trees are specified as girth size with their ‘girth’ being measured in centimeters one metre above ground level (ie 12-14cm) after planting. Reference is not usually made to the height of the tree, so if you need a certain height then confirm before placing the order. Not all species are commercially available in all sizes, as certain trees resent disturbance and need to be planted young. Check with your supplier for availability.The following sizes are described as:
Conifers and multi-stemmed trees are specified by height in increments of 50cm, e.g. 350-400cm
Trees can be specified as bare-root, rootballed or container-grown.
During the dormant season (November to March), many trees are available as bare-root or root-balled. Bare-root trees are lifted from open ground, soil shaken off and are supplied with the roots wrapped in thick polythene to protect them from drying out (occasionally, moss and sacking is used instead). The trees should be planted as soon as possible after lifting and usually establish well. This offers value for money and the trees are light to handle. Only certain trees up to certain sizes are suitable for this treatment.
Root-balled trees are lifted from open ground with the soil intact and the root ball immediately wrapped in biodegradable hessian and non-galvanised wire. The tree is planted with the wrapped root ball intact and the wrapping will rot, allowing the roots to develop. The tree suffers much less disturbance during handling, transportation and planting. A huge range of trees and sizes are available in this format and it represents good value for money if planting is to be carried out during the dormant season.
Container-grown trees are available all year round as they have a complete root system and can be planted at any time of year. Correct aftercare will be critical as they will have been accustomed to ideal conditions in the nursery and will suffer if not adequately watered in the period after planting.
Shrubs
Shrubs can be specified in various ways. The most common is pot size. This varies from 2 Litre right up to 50 Litre or more for specimen shrubs. The designer may also want to specify a height. This will usually be in centimeters above the ground after the shrub has been planted and would usually be somewhere between 60cm and 2 metres. However, there is a world of difference between a shrub with a single stem of 90cm and a bushy, well-grown one of the same height. In this case, it is possible to specify the number of ‘breaks’ or side branches a shrub must have.
Climbers
Climbers are usually specified by pot size, with 3 or 4 Litre containers popular with designers. They can also be specified by height (such as ‘minimum 2 metres’) or number of breaks (a clematis with three breaks will be a much bushier specimen than one with a single stem). Smaller plants may come with a single cane, but a three-cane tripod is better. Larger specimens may be trained onto a section of trellis and these will give an instant impact once planted.
Perennials
Perennials are usually specified based on pot size and would normally vary from a 9cm pot up to a 5 or 7.5 Litre pot. Some nurseries carry a limited range of 10 Litre perennials but these can prove quite expensive and better results are often achieved using smaller specimens. During the dormant season, perennials are available as bare-root and these can be good value. They do need to be stored carefully and planted promptly to get good results. Some perennials (hostas, for example) can be specified by the number of ‘eyes’ or growth points when supplied as bare-root.
Bulbs are usually categorized by their girth measurement in centimeters. This is the distance around the largest part of the bulb. Larger bulbs will perform better but will be slightly more expensive.
Fruit Trees
Fruit trees can be supplied in a wide variety of ways, including as a bush, a half-standard, a full standard, or trained as a fan, cordon, espalier or step-over. If the fruit trees are to be grown as trees then they can be specified by girth at one metre above the ground.
Hedging
Hedging can be supplied as ‘whips’ in the dormant season. These whips are bare-root and can be from 30cm to 150cm long and are great value for large quantities. Root balled and containerised stock will be available when the pot size, height or number of breaks can be specified. Mature hedging is also available when it is sold in one metre-long troughs in heights up to three metres. This will give an ‘instant’ solution but at a cost.
Summary
Plants are an infinitely variable product and are produced and presented in a huge variety of ways. By adding a detailed specification to the order you send to your supplier or nursery, you will be much more likely to actually get the plant you want; saving time, money and frustration.
Janine Pattison MSGD is an established garden designer and horticultural consultant working on a wide variety of domestic, commercial and public garden projects. Foe more information please see
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