Department: Glass
Dave was away so I helped sweep and water his area in Tropical. I gave all climbing vines a good spray - Clerodendron speciosum, an Epipremnum aureum etc. (it use to be a small house pot plant but was now as tall as the glass house - 12.5m). Temperate is closed today for work on the shading, so we had to move the Colour for Seed display into the corridor. Paul came and rearranged it and adapted if for that space - it was a mix of Cineraria x hybrida, Primula obconica, and Schizanthus pinnatus. We threw out what had passed over and it was refreshed with Calceolaria and Sweet Peas.
TREE ISSUES
Then I went to a professional development day on tree issues. A range of professionals including staff from Wisley gave talks. Brief overview - Jeremy Barrell from Barrell Tree Consultancy, talked about the law around working with trees, who's responsibility it was and what actions to take. The main thing was that if you are a responsible duty holders of managing land or an area with trees, one should assess things first like if tree(s) are in a high or low risk area - e.g. is there much people walking by or under it. Then one can call an arborist in to first do a visual assessment and make an appointment if necessary to do an more indepth inspection. But after this it is still up to the duty holder what course of action to take. Dependent on use and area - the frequency of inspection is a default of every 5 year, but more if circumstances require it.
Google map is good for finding before photos of tree pre damage.
Trees in a domestic setting - duty for homeowner is to do an informal check. They do not need to be able to clear ivy from a tree to see if there is damage to a tree that the ivy is hiding. They must respond to signs of poor health.
Things to bear in mind and to look out for in a tree - severe imbalance, big wounds especially if a tree is old. Drive by inspections are appropriate but staff should have the most up to date training to do adequately. Danger can happen in a split second.
Summer branch drop should be considered even if actions are not taken - this helps covers backs of large gardens like Wisley (Kew incident). Little is known why this happens yet - natural phenomena - generalities are that it happens in summer, there are 10 - 12 secondary characteristics that trees prone to this share - they are usually of a certain species - although this can vary continent to continent of course. Usually happens to old trees in decline, ones with over extended branches, a period of drought - 5+ weeks and then sudden storm one should be wary, there is a chance that SBD can occur in these conditions in a 24hr period after. Seems to happen in the day time.
There is no need to over react. Try to prune, fence and warn as preventative measures. Keep accurate records.
Chris Cadd from the Arb team gave an overview of how trees are managed at Wisley - different priority areas - inspection rotations of 1-3 years depending on foot traffic, condition of a particular tree. Extra checks after severe weather.
Dave Cashman talked about dealing with trees in landscaping, building development scenarios. Engineers generally don't realised that the roof plate of a tree is double that of a tree in width underneath ground and not as deep as people think - wide shallow root plates. He talked about creating sufficient barriers around trees, if this is not possible using things like putting a thick layer of woodchip down and skirting board over the top to spread out weights and prevent compaction on tree roots / aluminium road plates (though these have value and tend to get nicked), using advanced things like cell webs, arbor rafts and permavoid and filling these with clean stones. Also case studies of how businesses have worked with trees (almost building a house on stilts or building tree houses).
Diseases - honey fungus - deep cultivation might help break down rhizomorphs.
Phytophphora - if there is blackening of roots, there is a good chance it has this.
Acute Oak Decline is bacterial - dark oozing, rapid decline.
Massaria on london plane trees - shows as a soft rot, risk of branch drop hazard.
Ash dieback - wilting of leaves, dead dying tops - Spring and Summer. Stem canker, lesions.
Future risk diseases (not yet in UK) - Xylella fastidiosa - bacterium related, possibly spread by insects. Affecting Olive trees in Italy - may become an economic problem. Affecting rosemary in France - wide host range. Looks like leaf scorch, poor fruit production and chlorosis, similar to frost damage and drought. EU Commission has a 'host list' (approx. 250 plants) - result - new plant passporting obligations... DEFRA has more info.
Pests - Horse Chestnut Scale found on other deciduous trees too is found only on stems and only affects it aesthetically. Hydrangea Scale (affects Hydrangea, Acer & Prunus) on the other hand is on leaves and can affect vigour of plants. Sweet Chestnut Gall is damaging and needs to be reported.
Bartlett Tree Experts deal with OPM - there is possibility of using BT and chemical Diflubenzuron - that is not toxic to honey bees, lady birds etc. More potent sprays - but they kill everything. They are using 30m sprayers.