October 2012 - Richard Ravencroft: Trees - back to basics
At our October meeting, Richard Ravencroft spoke on “Trees – back to basics”
Here is a summary of his extensive and practical advice. If you would like to contact him, his website is www.ravencrofttrees.co.uk and Ravencroft Arboricultural Services can be found at Wheatfields, 6 Reepham Rd, Foulsham, NR20 5SL.
Richard dislikes topping and lopping, he would rather remove an ash tree than lop it drastically, which causes massive regrowth, stress and often, breaks. Silver birches likewise. Using chainsaws on fairly small trees causes cuts which rot, seal but don’t heal. Cuts introduce larger wounds, decay and rot.
A tree closes off a cut or damaged branch at a “branch collar”, he showed us examples on screen. The old advice to cut as close to the trunk as possible means the cut is too close to form a branch collar. Cut where a tree naturally sheds a branch. A callous should form over the wound and eventually close over. The aim is not to leave a stub. Richard does not paint the cut with anything, he leaves it open to the air.
We were shown on the screen striking photo’s Richard has taken of trees drastically reduced in size, lopped down one side only, all eyesores. On your next drive into Norwich, try and spot some!
Trees under attack
Horse chestnut trees suffer from leaf miner moth, which does little damage to its vigour and seeds, also a pathogen introduced in soil which causes decay and decline, pseudomonas syringae. A rod shaped, gram-negative bacterium with polar flagella, it is a plant pathogen which can infect a wide range of plant species. Look for stains, stem bleeding; this is water born and taken into the stem. It blocks the vascular cambrium, preventing the pumping of nutrients up the tree. Delamination of the bark allows other fungi to enter.
Oak trees may suffer from acute oak decline, phytopthora, which kills them after some 5 years. Look for stem bleeding. It also affects limes, Norway maple, larch and silver birch. Lots of larch are being felled in southern England.
Honey fungus, armillaria, will not touch a healthy tree but goes for drought affected ones. Black fungal bootlace like structures form with white mycelium.
The processionary moth is causing big problems to people, it fires spines into the skin, rather than to the trees it now inhabits in England. Do not approach.
Research on all of the above is now in progress and information spreads fast with the internet, far easier than when Dutch Elm disease began, hope to combat the problems.
Richard advises us to dig a hole usually a metre across, not deep as most tree roots stay near the surface. A square hole helps roots develop, round pots cause roots to ball, cut or tease them out before planting. Bare root stock is best. Do not stake a tree for longer than 12 to 18 months or the tree will not blow about at the base and will lean once released. Stake low at an angle to avoid going through the roots.
Keep the area around the tree clear of grass, bulbs, bluebells and leaves, they all retard initial tree growth.
A mature tree takes about 1,000 litres of water out of the ground every day!! If you remove a tree from sandy soil there will be few problems but from clay soil, expect wet ground. Some surface roots spread a very long way, eg. cherry trees. Willows are unsuitable for most gardens.