Goodness! What a coincidence! ;-)
I think the clue is that the advice given was by the GARDENER'S Question Time team. The 'problem' I was alluding to is that people often manage their woodland with a gardening mentality - as this is the only experience of land management most people in the UK have. A misperception of woodland (which unfortunately is also one of woodland's appeals to many people) is that it is timeless - an unchanging rock in a fast changing world. Natural woodland is actual very dynamic. If one native species is invading an area currently held by another native species, then this reflects either some aspect of the current environment that is changing, or a past event that shaped some aspect of the ecology of a place that is now being replaced by a set of more natural circumstances.
One could titivate any piece of land to put on a glorious show of bluebells. A sand dune in full sunlight with no trees - you could keep it moist with a hose pipe year round, you could 'weed' out the unwanted marram grass that kept 'invading' and the Gardeners Question Time Team could suggest a suitable program of fertilizing to keep the bluebells looking good. Realistically though after a few years a rational person would come to the conclusion that to keep gardening their sand dune, to put on the show of bluebells that they wanted to be there, was unsustainable, in terms of time, energy and effort. A person watching anyone attempt such a sisyphean task would think them mad.
The same is true of woodland that provides an ecological niche more suitable for one native species than another - as evidenced by the changing relative proportions of the two species within the community of the woodland's ground flora. You can unsustainably keep putting huge amounts of human energy (not to much other unsustainable resources) into 'forcing' woodland to be how you think it 'should', or just want it to be, but ultimately areas within such woodlands are going to become dominated by wild garlic. Drier areas will remain bluebell dominated, but the wetter areas are going to become wild garlic. If the owners want bluebell woods then perhaps they need to sell up and buy a woodland that better fits their dream woodland, rather than keep trying to force a square peg into a round hole.
I mean this by way of constructive critiscm rather than an attempt to initiate argument. You can't get away from the fact that woodland is dynamic - much more dynamic than people tend to believe, or expect, as the timescales over which much change occurs are typically longer than those people experience most commonly in everyday life. Patterns of drainage change - surface and subsurface water flows, seeps and issues can be changed by a single tree falling. When this happens one native species will gain an advantage over another, and the proportions of each species within an area of the woodland community will change. Wild garlic taking over from bluebells in a woodland is not disastrous - it's a natural part of woodland community dynamics. There is no way a person can justify taking unsustainable, and ultimately futile, action in an attempt to prevent this natural process and claim their action to be motivated by conservation aspirations - it only reflects that they want their bit of woodland to look like a picture postcard bluebell wood even if their woodland isn't naturally reflective of that ecological niche.
Now if their woodland was being invaded by gaultheria, rhodedendron, himalayan balsalm etc. then that can be disastrous, with negative impications that reach right through the natural ecology of woodland on many many levels and action to prevent, and protect against, such an invasion can be more easily justified...
