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Tree And Forest Links

Gardening With Attitude
By Mike Clark

Who Ate All the Trees?
Predators can do immense damage among young trees. So you may well ask, who would question the effectiveness of tree shelters?

If only life were that simple.

Who does the damage?
Perhaps the most obvious of damaging wildlife are rabbits and deer, but they are not alone.  A single hare can do as much damage as a whole warren of bunnies, snipping off the tops of young trees at the rate of 100 or more in a single night.  Then there’s the hidden menace of the vole. Trees which ended the growing season alive and healthy are dead at the Spring inspection.  Closer examination reveals a ring of bark completely stripped at the base.  This is the vole’s favourite winter hobby.

Let us not forget sheep and goats, although good management will ensure that fences are well maintained and kept intact. But I have known those who thought letting the sheep in among the trees to keep the grass down would be a good idea. I have met no-one who thought the experiment worthy of repetition.

Thanks to the attentions of deer, this tree is dead. Similar fatal damage can be done by sheep.

What’s on offer?
Probably the most familiar form of protection is the staked tree-shelter. These come in a variety of heights: 60cm will deter rabbits, 75cm is needed for hares, and 120cm or taller will be necessary where deer are a problem. These shelters will also protect against voles, as long as they are correctly erected with the base securely embedded in the ground.

A stout stake, well driven in and secured to the shelter with at least two ties, is essential, particularly in exposed situations.

Spiral guards are much less expensive than shelters. These are designed simply to be wrapped around the stem of the tree, but are best suited to larger planting stock than is normally used in young woodland planting. The stem of the tree needs to be of sufficient girth to support the guard. I have seen these used with smaller planting stock, with the addition of a bamboo cane to support the guard. This is a cost-cutting exercise with less than satisfactory results. With no real means of securing them, the first gale will result in these guards being distributed among your neighbours.

Mesh guards are also available, in plastic like the shelters, or made of wire mesh. Home made guards can be constructed from chicken wire – a great job to keep you snugly in the barn on a wild winter’s day. Like shelters, these need to be well staked and supported.

They have one distinct advantage over solid shelters for certain species, notably beech. Beech is prone to fungal infection in the enclosed environment of a solid shelter, and the chances of survival are greatly increased by the air circulation offered by a mesh guard. However, branches have a habit of growing through the mesh, and by the time you spot them, removal is nigh on impossible without damage to the tree.

If your only predator problem is the vole, there are vole guards available which are short, cylindrical lengths of plastic, slipped over the tree and firmly pushed into the ground.

A young alder tree in the cosseted environment of a tree shelter.

Apart from the risk of strangling the tree as it girths up, the main drawback with the vole guard is that is no deterrent to any other predator. And if you think voles will be your only problem, a penny to a pound you’ll be proved wrong at some stage. They may not be evident when the site is regularly worked, but once it’s quietly down to trees, all manner of creatures move in. However, vole guards are very effective against voles.

By now, you’d be forgiven for thinking I have reservations about all these forms of tree protection. And you’d be right. But let me make this clear – if you have a serious predator problem, shelters or guards are essential.

The flaw in the argument..
Shelters and guards, in my experience, can cause almost as many problems as they solve.

Believe it or not, tree shelters were originally developed and marketed, not as predator protection, but as growth accelerators. Indeed, they used to be commonly referred to as “growth tubes”. They would nurse the young tree in a protected environment, while the real world outside was cold, windy and generally hostile. The young tree would thrive in this environment, and shoot up rapidly.

Spotted the flaw in the argument yet?
What about the concept of hardening off?  Shelterbelts are by definition planted in the most exposed places. If you raise a plant in the cosseted conditions of your poly-tunnel, do you then put it straight out into the most exposed part of your garden you can find?

So pity the poor leading shoot which dares to pop its head out of the cosy shelter into a hostile north-easterly. Dieback in these circumstances is a regular occurrence. Leaders are lost, and trees eventually develop as shrubby bottle-brushes.

In the real world, a young tree will develop at a pace in keeping with its environment. The more exposed the site, the more slowly the tree will grow.  And the more sturdily.  The wind whipping the stem will promote girth rather than height, and encourage the development of deep anchoring roots.  The last thing we want to do is promote rapid, soft growth in an artificial environment.  You can’t cheat Nature.

How often have you seen substantial trees, still in their shelters, leaning at forty-five degrees, or even prostrate?

So this is a strong argument for using mesh guards rather than solid shelters. But that still leaves the problem of branches growing through the mesh.  And worse still.  There is the problem of the tree girthing up and filling the guard, which then embeds itself in the tree, gradually strangling it.  At least solid shelters are made to disintegrate after seven years or so, and in theory should split open under pressure.  This doesn’t always work, of course, as different species grow at different rates. Rapidly-growing species, like wild cherry, can fill a shelter in three or four years, long before it has become brittle enough to give way under pressure.

And of course, if shelters are left to deteriorate as they are designed to, the result is a plague of shredded plastic blowing across the countryside.

Dispelling the myth..
This is not a tirade against tree shelters, nor is it intended to be a negative article.  Tree shelters have a very important role to play, but I want the world at large to see both sides of the argument, and be aware of the disadvantages.  Knowing the drawbacks makes us better equipped to deal with them.

My point is to dispel the myth that tree shelters are an unqualified “good thing”.  They should be known, perhaps, as “tree protectors”.   That, perhaps, would be more descriptive of their role.

If predation in any of its forms is a threat, then some form of protection is essential.  But shelters should always be recognised as a necessary evil, because the accelerated growth they promote is a distinct disadvantage, not an advantage.  And shelters should never be used just for “shelter”.  If at all possible, grow your trees unprotected, lean and mean, hard and tough, and let them acclimatise to their situation in their own way and in their own time.

Cost Effective?
And finally . . . .

As a rule of thumb, a shelter and stake will cost six times the price of the tree within. Assess your predator risk as realistically as you can.  If you lose, and have to replace, a sixth of your trees every year for five years, you’ve broken even.

Your trees will be hardier and sturdier, and you will have a mixed-age woodland as a bonus!

Worth a thought, is it not?

© Mike Clark 2003.

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