We often hear from applicants and members of the public interested in our tree procurement strategy and, more generally, how we run our tree-planting programmes.
Where do we source the trees in our bundles? Why do we supply particular types of trees and not others? What else do we consider in relation to tree supply?
In this blog we take a look behind the scenes at NHS Forest’s approach to tree procurement and our strategy to ensure the efficiency and sustainability of our tree-planting programmes.
Where do NHS Forest’s trees come from?
You might be surprised that NHS Forest doesn’t operate a tree nursery of its own, and instead sources stock from commercial growers around the UK. British tree nurseries collectively produce millions of trees each year and we are able to procure a diverse range of tree species and specifications that fit around the planting objectives for our planting sites, comply with the requirements of our funders, and have been professionally grown to a high standard in a biosecure setting.
How does NHS Forest work with tree nurseries?
NHS Forest undertakes competitive procurement processes to ensure that we obtain value for money and that the stock and sundries being supplied conform to our specifications. One-off orders for larger projects may be sourced on the basis of ad hoc quotes, but we generally appoint a nursery supplier to fulfil all of the orders for a project or scheme meaning we can be certain that all recipients receive the highest quality stock consistently.
For the most part NHS Forest’s tree orders are distributed straight from the nurseries to recipient healthcare sites that we are supplying. Direct delivery in this way helps to reduce the carbon emissions associated with transporting trees and keep time in transit to a minimum.
How are trees produced by the nurseries?
NHS Forest’s trees are grown from seed collected within the UK; some may be produced from cuttings or grafted to create cloned copies of a parent tree. Common production methodologies (which account for the vast majority of our trees) are cell and bare-root growing, as outlined below.
Nurseries are carefully controlled environments, and when the seed has germinated young trees will be irrigated and treated to promote healthy initial growth. Regular monitoring for pests and diseases and quality control measures ensure that healthy trees are supplied for planting.
What is a cell grown tree?
Cell grown trees are germinated from seed in small tube-like containers – the eponymous ‘cells’ after which the stock is named. When the seedlings are ready for planting, the nursery removes them from the cells leaving the trees’ individual root systems enclosed in plugs of compost.
The stock is then graded into single species batches of uniform size – the trees in our bundles are 20-60 cm tall – and the plugs are wrapped to protect the roots and retain moisture in transit.
Why does NHS Forest use cell grown trees?
Since the 2023-24 planting season NHS Forest has specified cell grown trees for all of our native tree bundles as we have found it works very well for novice and volunteer planters, and especially where our guidance and supervision are at arm’s length.
The trees are sufficiently compact for the nursery to send the bundles as couriered parcels rather than on pallets easing order receipt and onward handling. Cell grown stock has a significantly longer shelf-life post-delivery meaning the trees can be stored for up to 4 weeks prior to planting.
As well as being more resilient to damage in transit, the uniform shape of the root plugs makes handling and planting more straightforward with less digging required; and there is also evidence for reduced transplant shock aiding good survival and growth rates of cell grown trees, and ultimately a higher proportion of successful establishment.
Since many NHS Forest tree recipients plant on a small-scale we hope that supplying resilient stock means we are setting up healthcare sites for success and maximising the return on time and effort that staff, patients and volunteers have invested in our trees.
What is a bare-rooted tree?
Bare-root or field grown trees are a more traditional form of nursery production; seed is sown directly into the ground, then once the trees have germinated and achieved a desired size they are dug up during dormancy (i.e. the winter months) and supplied without soil or compost around the roots.
As with cells, nurseries will grade and batch the trees for distribution with roots normally wrapped or bagged. Bare-rooted stock must be handled carefully to avoid damage to the roots, and the planting window is much shorter as the trees need to be planted within one week of delivery to be viable.
Why does NHS Forest use bare-rooted trees?
NHS Forest supplies bare-rooted stock for some larger planting projects and all orchard schemes (more on this below) and there are some good reasons for this despite the associated time limitations.
Field grown trees tend to have a larger root mass meaning they can be quicker to establish, less vulnerable to pests and diseases, and the absence of soil on the roots also means that stock is generally lighter which can be advantageous when planting at scale.
Bare-rooted trees are also often cheaper than an equivalent specification cell grown tree due to lower associated production costs, and it is more common for nurseries to grow on trees over multiple growing seasons and offer a wider choice of graded sizes and stock formats.
We have found that sites undertaking woodland creation projects comprising upwards of 500 trees see excellent results from bare-root stock, and the combination of economical pricing and a broader inventory of specifications permits a high level of order customisation corresponding to the unique characteristics and planting objectives for a given site.
What about fruit trees?
Unlike most of the UK’s native trees, productive fruit cultivars cannot be grown true to type from seed and must be grafted together using component parts from closely related species.
Grafts comprise two parts: a rootstock at the base, and scion wood that will become the upper fruiting section. Both elements are selected with particular characteristics in mind – the scion producing clones of the fruit from its parent tree, and the rootstock chosen to limit the ultimate size of the tree and to impart resistance to adverse conditions. Grafting is normally undertaken in early spring and the trees grown on over at least one subsequent growing season to allow the union to form between rootstock and scion wood and for the grafted tree to reach a given size.
NHS Forest’s fruit trees are bare-rooted maidens (single stemmed one-year old trees) graded at 1 – 1.5 m and with the same advantages and disadvantages outlined above for bare-root native trees. While potted fruit trees are commonly seen in garden centres marketed as a ‘year-round’ alternative, they are prone to transplant shock and significantly more expensive to send out from the nursery.
What is tree provenance?
Tree provenance refers to the geographical origin of a parent tree, whether as a source of seed or the progenitor of a genetic clone. Local adaptations enable tree species to establish in very different climatic and environmental conditions, and many UK natives are found over a wide geographical area extending far beyond the British Isles; for example the range of silver birch (Betula pendula) extends across Eurasia from the west coast of Ireland as far as Japan and Kamchatka.
Favouring local provenances helps to retain the legacy of genetic selections and adaptations by a tree species to the climatic and soil conditions in a given area. Choosing appropriate species and provenances for the site characteristics and local topography is a key management decision, and it is preferable to favour stock of local origin and from similar elevations when planting native trees.
What is the provenance of NHS Forest’s trees?
We specify that all stock used in our native tree bundles and for larger scale woodland creation schemes must be UK grown from indigenous seed. Given the geographic focus of our current funding we have favoured English provenances – principally seed collected in GB Region of Provenance 40.
NHS Forest supplies trees to healthcare sites throughout the UK, so it would not be possible to commit to supply entirely local provenance stock (i.e. from within the same region of provenance / seed zone / altitude band) in every instance at our scale of operation. We continue to explore the potential for more localised tree supply arrangements that would be compliant with the terms of our funders.
Provenances of grafted fruit trees (and most other non-forestry species) is less explicitly defined due to having a much shorter history of adaptation and localisation; in this context the NHS Forest tree procurement strategy requires that non-native trees originate and have been grown in the UK.
Why doesn’t NHS Forest supply larger trees?
It is natural to assume that bigger would be better when it comes to tree planting. Many tree recipients are seeking an instant visual impact from the new trees, and it’s not uncommon for us to receive feedback to the effect that planters were surprised at the size of the seedlings in our tree bundles.
NHS Forest isn’t anti-bigger trees and we do supply some larger saplings and potted specimen trees (principally as part of larger woodland creation schemes and as single commemorative trees). However there are a number of salient reasons that we don’t provide such trees more routinely as part of our tree procurement strategy.
Smaller trees are significantly easier to plant and maintain. There is no need to dig a large hole or stake the trees. Both cell grown and bare-rooted trees can be planted quickly and with minimal tools and equipment and don’t require routine watering in most cases. Larger transplants require lots of care and attention to ensure they are properly planted and can be more susceptible to pests and diseases.
Seedlings also have much better establishment rates and are more resilient to transplant stress. Lifting established trees inevitably causes loss or damage to root systems which can stunt their growth when replanted; large potted trees may struggle to adjust to the new soil conditions and are prone to pot binding (where roots form a dense, tangled mass when grown in a container for a significant period of time). Conversely the resilient root systems of younger trees are able to establish quickly post-planting and given sufficient time may even outgrow larger trees.
It is also worth considering the financial and environmental costs. Large trees require more time and resources in the nursery and are therefore much more costly to purchase, are more expensive to transport, and their carbon footprint (both to produce and distribute the trees) is significantly greater than for the equivalent number of saplings.
Why does NHS Forest focus on native trees in its tree procurement strategy?
Native trees are indigenous species endemic to a given area or region; in the UK this means species that recolonised the British Isles 10,000 years ago at the end of the last Ice Age, undergoing genetic adaptation and co-evolution with local ecological systems. Native trees are therefore best suited to the UK environment and able to support a huge amount of biodiversity; for example, oak trees may host 2,300 other species including 326 species solely dependent on oak for their survival.
Native trees also offer myriad unique benefits for human health – and you can find more details about some of those benefits in our blog about why humans need trees.
What is plant biosecurity?
The UK has witnessed a dramatic increase in accidental introductions of non-native tree pests and diseases since the early 2000s with significant implications for both new planting and established trees and woodland. Pests can easily be transmitted accidentally by individuals, vehicles and equipment, in soil or on plant material; microscopic organisms may also spread in water or can be borne by the wind.
Biosecurity refers to measures undertaken to prevent the spread or introduction of pests and diseases; any tree is potentially susceptible to plant pathogens and infestations of invasive or endemic pests, effective biosecurity practices help to minimise the risk of contamination.
What is NHS Forest doing to promote biosecurity?
Biosecurity is at the heart of NHS Forest’s tree procurement strategy. We source all our stock from growers that are compliant with the Plant Health Management Standard, have proactive biosecurity policies in place, and operate from pest and disease-free areas of the UK. All stock is subject to routine inspections before leaving the nursery. In addition we specify UK grown plants and have excluded imported stock as a potential pathway for the transmission of non-native pests and diseases.
Are NHS Forest’s trees certified organic?
Although a few growers do operate on a no-chemical basis and there are ongoing trials focused on developing a scalable field system for organic forestry trees, at the time of writing organic principles are not defined in a meaningful way for non-productive trees. The NHS Forest tree procurement strategy does not currently specify that productive fruit trees be certified organic, although we will keep this position under review.
Which agrochemicals are commonly applied by tree nurseries?
Most nurseries use some agricultural chemicals in the course of growing trees; exact products and usage will vary in line with production, but common applications for tree production would include:
- Pesticides including but not limited to herbicides, insecticides, and fungicides which are used to regulate pests and limit associated damage to the trees.
- Soil amendments, most commonly fertilisers (synthetic compounds that supply nutrients to the soil / growing media) and soil conditioners (added to improve soil’s physical qualities).
- Soil sterilants, a specific type of herbicides used to mitigate weeds in seed beds; some growers have begun to switch to non-chemical alternatives such as steam and flame weeding.
- Other substances that are used to control the development of stock such as phytohormones used as regulate growth and defoliants applied to push deciduous species into dormancy.
Are agrochemicals products really necessary for tree production?
Agrochemicals are something of a necessary evil for most nurseries. Clearly there is an economic justification for products that enhance the yield of saleable trees, but plant health is generally the main rationale for most growers with pesticides being used to alleviate the risk of pests and diseases being transmitted into the wider environment and other products to enhance the quality and consistency of stock being produced, and by extension help increase the rate of successful tree establishment.
Responsible producers employ strategies to keep their use of such products to a minimum, both for environmental and financial reasons. Furthermore spraying is largely confined to the growing season when the trees are in leaf, meaning that stock supplied dormant (i.e. with no leaves) will retain only trace quantities of any agrochemicals that may have been applied.
What is NHS Forest’s policy on the use of agrochemicals?
Specifying stock produced with atypical chemical usage would likely restrict the quantity and quality of stock available for purchase and has the potential to act as a conduit for pests and diseases. Until such time as a standard for chemical free tree production has been formalised and demonstrated effective in mitigating plant health issues NHS Forest will continue to supply treated stock, although we will keep this position under review.
What is NHS Forest’s policy on peat use?
NHS Forest’s tree procurement strategy specifies that all stock be produced using 100% peat-free growing media. Peat-based compost has traditionally been widely used by tree nurseries, but extraction is detrimental to wetlands and the wider environment; damaged wetlands are a major source of anthropogenic CO2 emissions and Defra has confirmed a phased ban on horticultural peat on the basis that its continued use for plant production is unsustainable.
What is NHS Forest’s tree procurement strategy regarding plastics?
We have another blog dedicated to tree shelters, but NHS Forest has also given some consideration to the plastics associated with tree order fulfilment.
While there is no single format for tree deliveries (this varies depending on the number of trees and between suppliers) as a rule of thumb NHS Forest’s smaller orders are packed in cardboard boxes, and larger orders will be sent out on pallets. Most nurseries also use some plastic materials to secure the consignments – for example, strapping around boxes or shrink wrap on pallets – and the trees will be supplied in either stretch wrap or forestry bags to protect their delicate root systems and facilitate moisture retention in transit. This remains necessary to ensure viability of the stock and integrity of packaging throughout the journey to site. We are working with suppliers that have proactive plastic reduction strategies in place, and we will continue to explore all opportunities to minimise the environmental impact of transporting trees from the nursery to healthcare sites.