Trees in Towns II “Average loss rate of 23% for newly planted highway trees and 24% loss rate for newly planted trees in public open spaces” If this statistic is accurate large proportions of resources are being wasted
What is specified and what is omitted ? Co-dominance lack of stem taper
Central Leader Stem Good straight leader Perhaps!!! 1.8 meter clear
Root-balled Bare-root Production system 3 primary systems used in the UK
Bare Root Advantages Investment per plant is low Cost of plants to the consumer is low Plants are lightweight, making shipping economical Bare-root
Bare Root Disadvantages Planting time for digging and transplanting is short Only deciduous species easy to transport are suitable No root activity occurs until bud swell in the spring Larger plants have a higher mortality and the survivors are slow to recover Plants need to be stress tolerant and capable of rapid root regeneration following transplantation
Bare root species selection Trees with Fibrous root systems transplant better than those with coarse roots Fraxinus excelsior, Prunus avium, Sorbus aucuparia and Acer platanoides have fibrous root systems Quercus robur, Carpinus betulus and Fagus sylvatica have coarse root systems Fibrous roots are suggested to be more prone to desiccation in the period between lifting and planting (SPECIFIABLE) (Struve, 1990)
‘The Planting of Trees and Shrubs’ (Watson & Himelick, 1997) Suggests evidence of lateral root development is a good indicator of plant health in bare root trees (SPECIFIABLE) Stock with strong tap roots and little lateral development are unlikely to survive (SPECIFIABLE) Guideline indicator: Root spread should equal 4 x’s the stem circumference (SPECIFIABLE)
Rootballed Advantages Digging and transplanting season is extended compared to Bare root (BR) Plants with poor survival rate as BR can be transplanted with moderate success Soil ball placed in the landscape creates minimal textural and water movement barriers Plants can be dug ahead of time and stored above ground, extending transplanting time
Rootballed Disadvantages 98% or more of the root is lost at digging Digging is limited to the dormant season for all but a few very tolerant species Some species cannot be transplanted with satisfactory survival rates Labour is intense and needs to be skilled Soil type and moisture conditions can limit digging Root balls are heavy and awkward to transport They must be kept most, but not wet during handling and shipping Planting must be completed in the spring before natural bud break for the species
98% of root system can be lost when trees are dug from the nursery using standard methods Watson and Himelick (1997) What is actually inside the Rootball?
When planting rootballs the following is true. Can only absorb water from a soil that they have proliferated Water contained in soil outside the rootball is largely unavailable Root system must ‘grow into’ the soil outside the rootball before water there is useful to the plant (MAINTENANCE:)
Root generation and water uptake Can take up to 7 weeks for new roots to be initiated following digging Up to 13 weeks before the regenerated roots are capable of absorbing measurable amounts of water from outside the roortball Up to 20 weeks until the soil moisture is absorbed at similar rates from rootball and backfill soils Water available to newly transplanted trees is only enough for a few days at a time (MAINTENANCE:)
Rootball production The rootball system of production evolved around the principal of root pruning. This system is often referred to in nursery catalogues as 3 x transplanted. This is rarely specified……….. (SPECIFIABLE)
Rootball specification Hartman et al (2000) produced a table outlining the ideal rootball diameter and depth to enable successful establishment A tree of 14-16cm girth should be supplied with a rootball of 70cm diameter and depth of 60cm How many rootballs supplied into the market would meet this specification? Such a rootball would weigh 300lbs, an equivalent 85L 14-16cm container grown tree would weigh 198lbs (SPECIFIABLE)
Rootball dimensions in relation to tree size at purchase Caliper (inches)Rootball diameter (inches) Rootball Weight (lbs) 224392 2.528624 332867 3.5381216 4421877 Watson & Himelick (1997) Principles and Practice of Planting Trees and Shrubs
Rootballs in USA Note Root balls stored upright Individually irrigated Position and height of wire Stem taper
Container Grown Trees Advantages The root system is entire and undamaged The trees can be moved and planted at any time of year, although less maintenance is required if they are transplanted during the autumn and winter Trees are generally easier to handle and store Post transplanting stress and shock is reduced to a minimum Earlier aesthetic rewards are achieved in the landscape
Container grown Trees Disadvantages It has been claimed that container trees require additional irrigation during the establishment period There are potential problems at the soil-compost interface There is always the potential for root girdling within the container. The length of time a tree spends in a container is critical. All systems produce root girdling. At Barcham we have introduced a concept which we call ‘shelf life’ (SPECIFIABLE) It has been argued that container compost media contains none of the naturally occurring mycorrhizal and bacterial elements to the detriment to post transplanting establishment
What is never specified? Container Grown Bare-root Rootballed ? ?
Stem taper Much nursery management is comparable to woodland management with trees closely spaced, elongated with little of no stem taper.
Stem taper Barcham Birch showing defined stem taper
Where the tree as actually grown Many trees supplied into the UK market have spent no more than a few minutes on the supplying nursery as they are transferred from one lorry to another (SPECIFIABLE)
Plant Health All the above can be specified but none actually ask the question as to whether the tree is actually stress free at the time of supply. It is a bit like buying a fridge by size and colour without actually asking whether it works or not.
Plant Health Arboricultural Research and Information Note 126/94 Arb entitled ‘Assessing the Quality of Broadleaved Nursery Stock’ stated: “the early survival of trees in any planting is determined largely by the quality of the planting stock and post planting aftercare However assessment of tree quality relies on external morphological features”
Plant Health It continues.... ‘”many trees which meet the morphological criteria are dead or moribund before planting” Insley 1982 “Further work is aimed at developing a simple easily determined PLANT QUALITY INDEX for broadleaved planting stock that will reflect the ability of plants to survive outplanting”
Plant Health Up until now this has not happened. BUT Spadmeter Flourimeter
Plant Health In the Arboricultual Newsletter Issue 146 Autumn 2009 Dr Glynn Percival reviewed the following as plant vitality tests which might be useful. Shoot and root electrolyte leakage Root growth potential Chlorophyll fluoresence Chlorophyll content Twig starch concentration Infra-red thermometery
Plant health At Barcham we have tested over 15,000 trees on the nursery Chlorophyll fluorescence Chlorophyll content Electrolyte leakage (SPECIFIABLE) This will provide a benchmark as to plant health on the nursery and at the time of supply.
Specifications: The future From the above it is perhaps possible to visualise specifications which will include in addition to girth and clear stem. Production method and criteria to ensure that method is being practised correctly Stem taper Height/ stem diameter ratio Production site Chlorophyll fluorescence Chlorophyll content Electrolyte leakage Length of time actually on supplying the nursery
Ultimately …………… The Choice is yours But asking the right questions and preparing comprehensive specifications may avoid in the future the current ‘Trees in Towns II statistics
Any Questions? What other industry would accept a 25% failure rate as the norm and survive?