Working with chainsaws

Working with chainsaws

Chainsaws are potentially dangerous machines which can cause fatal or major injuries if not used correctly. It is essential that anyone who uses a chainsaw at work should have received adequate training and be competent in using a chainsaw for the type of work that they are required to do.

In recent years (in forestry and arboriculture) direct contact with a chainsaw has caused 5 deaths and many serious injuries. These do not include the high numbers of other types of accident that occur during felling, pruning and other related work.

HSE’s investigations show that most fatal and major injuries involve chainsaw operators taking shortcuts and not following good practice guidance. Usually the reason is to save time.

How to remove a tree stump

How to remove a tree stump

Physical stump removal is the best solution. Ideally the stump should be removed entirely, but if this is not possible alternative methods usually give satisfactory results.

For smaller trees the stumps can be pulled out with a winch. These can be hired by gardeners with the knowledge to use them safely. For leverage it is necessary to leave a good sized stub on the stump (up to 1.2m (4ft) high) rather than cutting it off at ground level.

Grubbing out by hand or mechanical mini-excavator removes the majority of the root system. Removal is easiest if trees are cut down so that a significant length of trunk remains to give leverage to help in removal. Landscape contractors are often skilled at stump removal, but you can hire mini-excavators and operators separately.

Alternatively, machines known as stump grinders will mechanically grind out the main root plate, leaving fine sawdust. Although stump grinders can be hired, they are potentially hazardous and are only for gardeners confident that they can use machinery safely. Some roots will inevitably be left in the ground but the majority should eventually rot down.

It is worth specifying how deep you would like the stump ground to. Shallow grinding, 20-25cm (8-10in), is normally sufficient for laying turf, but you should allow for deeper, 30cm (1ft), or more if replanting or landscaping. Also think about what you want to do with the sawdust. It can be left to fill in the hole, used as mulch in other areas of the garden, or taken away by the contractors. Specify which of these you would prefer before the work is started and be sure to have any diseased wood removed completely.

Should you like to replant the area it is best to remove bulk of the sawdust and fill the hole created by stump grinding with topsoil. If larger amount of sawdust was accidentally mixed with the existing soil it is usually worth adding nitrogenous fertiliser prior to planting to counteract possible problems with nutrient lockup. For example, consider mixing in chicken manure pellets or sulphate of ammonia.

Methods to avoid

We do not recommend burning down stumps in situ. They are usually too wet for this. Applying nitrate fertilisers also does not improve their burning qualities, or speed up rotting, even though these fertilisers are oxidising agents.

How to apply stump killers

Stump and root killers currently on the market are those containing glyphosate (e.g. Scotts Roundup Tree Stump & Rootkiller, SBM Job done Tough Tree Stump Killer (soluble sachet only), Doff Tree Stump & Tough Weedkiller and Westland Deep Root Ultra Tree Stump & Weedkiller) or triclopyr (Vitax SBK Brushwood Killer).

  • Always follow the manufacturer’s preferred method. This may involve treating the entire cut surface of the stump, drilling holes around the living edge of the stump to pour the granules into, or using a chisel or axe to make wedge-shaped incursions around the edge of the bark (often used for standing trees). These notches can then be filled with granules or brushed with the liquid weedkiller
  • The best time to apply stump killers is from autumn to winter. Avoid treatment in spring and early summer when the sap is rising
  • Apply a weedkiller directly to the stump, concentrating it in the outer ring of live tissue just beneath the bark
  • Weedkiller is best applied to fresh stumps, as live tissue is needed for its uptake. If the stump is only a few weeks old, you may be able to expose live tissue by cutting the top off to expose a fresh-cut surface

Finally, cover the whole top of the stump with a plastic sheet to keep off the rain and secure in place.

Seasoning Wood for Fuel

Seasoning Wood for Fuel

Seasoning wood for fuel is an art rather than a science but much is common sense. If round timber is stacked across drains under the drip-line of standing trees in the middle of a humid forest the chances are that it will be as wet or wetter after two years than it was when it was put there. On the other hand, with a little planning and timely action, those logs could have been turned into excellent fuel in half that time. The following is a general guide to the seasoning of wood for fuel. For detailed advice on individual aspects of wood fuel preparation (cross cutting & stacking, use of firewood processors, chippers, etc) refer to the Guides produced by the Health and Safety Executive, all of which are available free online (www.hse.gov.uk/pubns/forindex.htm).

The prime objective of seasoning is to reduce the moisture content (MC) of wood to make it suitable for use as fuel. Confusingly there are two very different ways of expressing MC, dry basis and wet basis. For clarification the two different methods are described in a note at the end of this guide but the guide will stick to wet basis. At 50% MC wet basis half of the unit under consideration is wood and the other half is water.

One of the most important ways of reducing the MC of firewood is to fell trees at a time of year when they contain least moisture, during the winter, when the sap is down. If felling has to be carried out during the growing season there is some evidence that leaving the branches, complete with leaves or needles, attached to the tree until they wither can draw moisture out of the wood. This approach is called sour felling.

Conventionally firewood is felled in the winter with a MC of around 50% and must be seasoned down to between 20% and 30% to make it suitable for use as fuel in smaller combustion systems like wood burning stoves. Larger combustion systems can burn wetter wood but they sacrifice considerable amounts of energy for the convenience of using such fuel. A tonne of wood at 50% MC has a calorific value (CV) of only around 2,300 kWh but a tonne of wood at 20% MC has a CV of over 4,100 kWh. In money terms, if a kWh of heat is worth 5p then a tonne of wood at 50% MC is worth £ 116.38 but a tonne of wood at 20% MC is worth £ 206.55. The higher value takes a bit of time and effort to achieve but the rewards are clear.

Writing about firewood in the early eighties Geoff Keighley identified three states of seasoning: Fresh felled; air dry; and house dry. Wood holds water in two different ways, inside the cells and within the cell walls. Air dry is a pragmatic description of the point at which all (or most) of the water has been lost from inside the cells, around 25% MC. House dry describes air dry wood that has been stacked indoors for a short period, perhaps 20% MC. After felling timber should ideally be extracted to an exposed site outside the woods where it can be stacked off the ground on bearers, facing the prevailing wind. Dense hardwoods with smaller cells like oak, beech, sycamore and hornbeam need to be seasoned for two summers and a winter. Conifers and fast growing broadleaves like ash, birch and poplar, with larger cells, can often be seasoned in one spring and a summer depending on the weather.

Stacked logs would benefit from covering during the winter to prevent reabsorption of moisture. Anecdotal evidence suggests that it is particularly important to prevent snow from settling on seasoning timber.