Yew has a reputation for being indestructible, and given fair treatment, there are yew trees planted today that will still be alive when mankind is sailing around the solar systems* in fusion powered, garden filled hyper-barges
At the same time, Taxus baccata is like any living organism and can die prematurely. Because it is so tough, you may be able to save your tree or hedge with swift action. Here are a few reasons why yew dies when it should not.
Dogs and Cats kill Yew Trees and Hedging
Well, what comes out of their furry back ends harms younger plants. Cats like to excavate holes in the same place area and bury their "raw lion dung topdressing", which from the tree's perspective is slow poisoning.
Dogs are potentially worse, in that where one marks a spot, others seek to follow. Then, according to tradition, the first one comes back to mark their marks with his mark, and yews do not like uric acid on them.
A cheap and easy solution to this is to pile dead bramble or other thorny plant cuttings along the hedgerow for its first few years.
Yew dies by drowning
English Yew grows just about anywhere - there is a lovely yew hedge by the river Wylye that is flooded whenever it rains. But then the ground drains. The moral of the story is that you can plant a yew hedge in any kind of soil as long as the roots do not sit in water for extended periods of time. Dig a trench in solid clay and fill it with lovely compost and topsoil, and you have created a death trap for your hedge. The clay does not drain and the trench will fill with water and stay that way. So if you are planting on poorly drained soil either ensure there is drainage or DO NOT PLANT IN A TRENCH. Clear the ground, and plant bare-rooted stock in slits which you close up firmly when you have finished. There is an excellent planting video on our site which shows the technique.
The salt that is spread on roads whenever there is a hysterical reaction to the possibility of freezing conditions is bad for all plants. Full stop. If your hedge is in a place where thawing ice, snow or just rain will run off, then think about a wall or fence. Most plants hate salt in the quantities that can collect in some places at this time of year. If your hedge will not suffer from direct run-off and only gets splashed by traffic, go out the day after the thaw and wash it with a hose until it has established for at least 12 months. Given our climate, you probably will not have to do this at all.
Root rot is caused by a number of organisms most notably Phytophthora. Some form of phytophthora exists in all soils (a bit like cold germs in tube trains...). Just because it is there does not mean your yew plants will die, like most diseases it needs the right conditions to cause damage. It is always best, therefore, to improve the soil with organic matter to help drainage and to encourage new root growth. Expensive plants like yew are also helped if you use a mycorrhizal additive when you plant - it is not cheap, but the benefits are considerable.
As with Phytophthora, there are a number of forms of Honey Fungus, not all of which are dangerous to plants. However, the ones that are, kill any tree or woody plant whose defences they penetrate, yew included, although the number of reported deaths of yew caused by honey fungus is very few as it is extremely resistant. Honey fungus travels underground and attacks trees and hedge plants through their root systems. If you cleanly trim off any broken bits of root with secateurs before planting, and if you improve the soil with organic matter, you reduce the chance of a honey fungus attack.
Watch your hedging grow, and enjoy
*Assuming that space is in fact real (can't trust anyone these days).