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Hillier Guide To Choosing Your Trees

To choose the right trees for your needs a number of factors need to be considered, including ultimate size and suitability, soil type and the climate and corresponding tree hardiness.  Here, we take you through the key considerations to help you choose the right trees for your project.

1. Select a Tree

When selecting tree species for your project, certain factors need to be considered:

Species Characteristics
Berry, flower, leaf, autumn colour, whether it is a native species etc. Our tree descriptions are factual, informative and honest to help you make the best choice.

Size of tree
Our descriptions specify whether the ultimate tree size is small (5-10m), medium (10-20m) or large(20m+).

Size after 25 years
Since the lifespan of various species can be anything between 30 and 300+ years, we indicate the approximate size likely to be reached in 25 years.

Suitability to site conditions
For all our trees, we indicate tolerance of dry or wet soils and lime and a hardiness rating. See below for full explanation.

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2. Suitability for Conditions

So you can establish if a tree species is right for your site, we indicate tolerance of various conditions on our A-Z tree descriptions. This relates to plants once they are well established on site. All plants require adequate irrigation, at least for the first season, to become established.

Dry Soil Tolerant
• Indicates trees that will tolerate levels of water stress as experienced in an average British summer on a light soil.

• Some trees are also categorised as ‘drought tolerant’ and will withstand the most extreme drought conditions likely to be encountered in the UK on any reasonable soil.

Wet Soil Tolerant
• Indicates trees that are perfectly happy in heavy clay soils and will withstand short-term (2-3 days) water-logging.

• Some trees will withstand even prolonged (1-2 weeks) water-logging, though few, if any, of our trees will withstand permanent bog conditions.

Lime Tolerant
• Indicates trees that will succeed on an alkaline soil, containing or overlying chalk or limestone, provided there is at least 40cm depth of soil.

• Few of the trees listed will do more than ‘survive’ on very thin chalk soils.

Hardiness Rating Guide
The factors affecting hardiness are not well understood, either individually or in combination and certainly involve a great deal more than low temperature. For this purpose, we have assigned a rating to each plant based on experience and observation over many years and indicating practical terms, the sort of climatic conditions in which the plant could normally be expected to succeed.

Hardiness 1: The ‘Fragile Few’
Suitable only for the mildest areas of the country (e.g. Southern Counties, sheltered coastal areas further north) and local favourable microclimates. Often spectacular in flower and useful for this in the right location. Unfortunately too tender for general planting and for this reason, we offer few varieties of this hardiness.

Hardiness 2: The ‘Townies’
Given a reasonable degree of shelter from the north and east, these plants are perfectly happy in all but the coolest inland areas. Much used in the urban landscape where the microclimate usually offers protection. Unsuitable for exposed sites.

Hardiness 3: The ‘Infantry’
The tougher ornamentals. This group comprises a broad palette of plants suitable for mass planting anywhere in the UK. The foot soldiers of urban landscape design, but usually inappropriate for the rural environment.

Hardiness 4: The ‘Gladiators’
The real ‘toughies’. Will withstand anything the British climate can throw at them except perhaps physical damage from gales.

3. Specification

Once you have selected your tree species you need to consider the following:

Size of tree when planted
All trees are specified as girth size being measured in centimeters one metre above ground level.

Semi-mature trees start at 20cm girth and progress  in increments of 5cm.

Conifers and multi-stemmed trees are generally measured by height in increments of 50cm. When conifers are specified by girth size, this indicates a clear stem is required.

4. Root Specification

We recommend how trees should be specified and this is reflected in the availability guide. Root specification options are either:

• Bare-root (BR)
• Root-balled (RB)
• Container grown (CG)

Bare-root trees (available November – March)
Bare-root plants are lifted from the ground, either by hand or by mechanical means. Trees will be undercut and lifted, keeping as much of the root system intact as possible. Even though some roots will be lost on lifting (approx 25%) a well grown and regularly transplanted tree will have more  than an adequate amount of roots to flourish.

Co-extruded polythene should be used: these are bags which are extra thick, black inside and white outside to reflect heat. At Hillier Nurseries all bare-root trees are placed in co-extruded bags at the time of lifting in the field. If this was not done the delicate fibrous roots would dry out very quickly. This may have an impact on the tree’s health. Always specify coextruded bags for bare-rooted trees and check that your trees are being handled correctly.

• Value for money
• Light to handle
• Quick to establish with correct after-care

Points to remember:
• Only trees under 18-20cm girth should be specified bare-root and not Fagus, Betula, Quercus, Liriodendron, Liquidamber, Ginkgo, Parrotia and all conifers. These must be specified root-balled or container grown.

• Trees must be sealed in double thickness, co-extruded polythene bags after lifting.

Root-balled trees (available November – April)
The tree is lifted from the ground with the soil intact around the root system. On removal from the ground, the root-ball is wrapped in biodegradable hessian and non-galvanised wire. The root-ball should be planted intact with both left on. If the hessian and wire are close to the stem of the tree, it would be beneficial to cut the wire and hessian and pull them back to the shoulder of the rootball. Once planted, the wire breaks  down and the hessian rots, allowing the root system to develop.

• The root system once lifted will not be disturbed
• The packaging will bio degrade
• Root-balled trees are protected from the rigours of commercial planting
• Suitable for underground guying

Points to remember:
• All field-grown trees 18-20cm and over must be root-balled
• Certain species that are field-grown must also be root-balled, e.g. Fagus, Betula, Quercus, Liriodendron, Liquidamber, Cercidiphyllum, Eucalyptus, Ginkgo, Parrotia and all conifers
• Root-balled trees should be planted with hessian and wire left on to maintain the integrity of the root system

Container Grown trees (available all-year-round)
Container grown trees have a complete root system and should therefore establish well once planted. Trees are lifted either bare-rooted or root-balled between November and March and placed in a container, then grown for at least one growing season. For example, a tree potted in January would be fully rooted and ready for planting by September.

• No root loss during lifting
• Planting can take place all year round
• Hillier-handles make handling on site easier
• Suitable for underground guying

Points to remember:
• Quercus ilex should always be specified as container grown
• Trees will be accustomed to irrigation on demand and after-care is crucial
• Hillier trees are peat-free

5. Check Availability

Not all species are commercially available in all sizes. Please contact us for current availability.

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