February 27, 2015

In memory of trees


This last week I have been fortunate enough to pay a visit to an established UK tree nursery: Hilliers in Hampshire.  Hilliers are about much more than trees with a portfolio of garden centres, cash and carry and shrub and perennials supply. Here, I am focusing upon tree supply as this was the purpose of my visit. Despite high hopes for sun and blue skies, I was disappointed to realize that it rains in Hampshire as well as Manchester! In fact, it pretty much rained the whole time I was there, so the tagging and inspections were a wet and muddy job!

Space for trees-the growing bit

Hilliers are one of the largest UK tree growers and grow all their trees (around three quarters of a million!) across several sites in Hampshire, covering a total of 600 acres. I spent most of the time with Jim Hillier on their largest (250 acres) and distribution centre site: Home Farm. As a designer, I am keen to source from good UK suppliers wherever possible.   These sites were chosen for their sandy loam soil type and Hilliers identified those sites where the soil matched and is similar to the key European tree nurseries to ensure the quality of stock that they sought for the UK market. This soil makes for the best production of trees with fibrous root systems required for healthy trees that can be successfully transplanted to a garden or other landscape situation.  The trees are grown in rows in the open ground and at increased spacings depending upon the age and size of the tree. Over their development they are transplanted and undercut (pruning back the roots whilst in situ) a number of times and it is this process that influences the tree’s ability to survive when planted in a landscape scheme. It is interesting to know that no tree is available for sale until at least 6 years after the start of its life! Therefore most trees sold are considerably older than this (e.g. a 20-25 cm girth pleached hornbeam with 5 tiers has been on the nursery for 11 years ! With a range of stock sizes from 8 cm girth to 80 cm you can imagine the span of ages!


So much kit!

With the size and quantity of trees at hand, it is not surprising that they have some pretty impressive lifting gear including this contraption and associated tractor!


And with the need to grow the stems straight and to develop trained forms, they need a surprising number of canes. Apparently when a new canes consignment arrives, it takes 4 men 2 days to unload! All frames are made by hand on site and the horticultural-qualified staff are trained in-house to achieve the standards required. Closed sided delivery vehicles are another order of the day when delivery of trees across the country is part and parcel of the business


Variety is the spice of life

As you would expect from such an established tree nursery, there were some exquisite specimens to see as well as some of my favourite forms. Genera include Betula species eg. B. Utilis Jaqcuemontii Grayswood Ghost, as multistemmed trees; Ulmus ‘New Horizon’ a Dutch-elm-disease-resistant elm; various Prunus species including multistemmed serrula; multi-stemmed Acer griseum, Single stemmed Planus x acerifolia (London Plane) grown for London streets and therefore with a clear stem such that London buses can pass underneath!, pleached forms of a number of varieties including London Planes, Tilia species, Carpinus betulus (also as columns and arches), multistemmed Pinus sylvestris and the wonderful parasole forms of prunus and platanus. To name a few!  As you can see, the grey and wet day did nothing to inspire wonderful pictures but they at least serve as a reference!



Supply of trees

It is at this time of year that the bare root season ends as trees start to come into leaf . There were examples of every type of tree supply on the nursery so no matter what time of year you are planting and whatever the particular detail of your project, you should be able to source appropriately. Here are the options:

Bare Root

These are suitable for woodland planting, young hedging etc. Field grown younger trees are cut out of the ground and the soil shaken off to economise on weight. They are the cheapest type of supply but with a significant failure rate; good for easy-to-root varieties and broad-scale planting, only planted in winter.

Root balled

These are field grown trees cut out of the ground and wrapped in hessian sacking and non-galvanised wire, the soil is left intact and the whole root ball is planted. Quality growers such as Hilliers have regularly transplanted and undercut the stock before final lifting but these trees have lost a lot of their fibrous roots in the lifting process. They can only be planted in winter; this method does require careful aftercare.


Similar to the container method, Hilliers uses bags for ease of handling (and maneuverability). This method is perhaps better than bareroot, rootball or conventional pot, but inferior to air-pot grown trees. They can be planted at any time of year.

 Air Pots

These are the crème-de-la-crème of tree growing with a sieve of recycled and recyclable plastic that is textured with cones like an egg carton used as the pot material. There are small perforations in each cone so that the roots are funneled; a dense fibrous root system is stimulated by the constant ‘root pruning’ that happens when the roots pass through the holes and then dye back on exposure to the air. Hilliers and other good quality tree suppliers use this method, especially for the larger trees.




Tagging trees

As a designer, I prefer to go and select the trees for my client and I did this on the nursery at Hilliers in order to reserve some pleached trees for subsequent digging up and root balling.  These are trees that are grown as a hedge on stilts and have tiers of branches that form an espalier.  My selection was based on those pleached trees that had shoots and branches all the way to the edge of the frame, had a balanced head that would not have gaps when in leaf and had a clear stem as close to 2 m as possible (and all equal) given that they are going in front of a 2 m high wall and my client wants screening above the wall.



If you get a chance and haven’t already done so, it is well worth visiting specialist  nurseries to find out more about how they grow trees and their working practices. As a designer I find it an invaluable way of understanding best practice, specifying and sourcing quality trees and plants.

I am a Chartered Landscape architect and garden designer with a keen interest in contemporary spaces, roof terraces, courtyards and kitchen gardens as well as all manner of garden and landscape projects.  I  blog regularly about aspects of garden and landscape design and growing food on our boutique allotment.  You can also follow me, Liz Ackerley on Twitter @poppyheadC,  or like our facebook page  www.facebook.com/poppyheadconsultancy  where you will find lots of tips and ideas related to gardens.  Also check out my projects and approaches to design here on my website:  www.poppyheadconsultancy.com

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