Monday 29 October 2018

Trees as weeds

No woody weeds in Cathi's field
Self seeding trees are a real nuisance. They are nature’s first salvo in an ecological succession that might make your garden a wood.
They are a real nuisance when in a good year (for nature) they appear in their thousands in lawns, paths, nooks and crannies. They are quite tricky to control.

Unwanted rhus sucker
Even worse are certain trees such ailanthus and rhus which when chopped down produce copious suckers from the inevitable root cuttings made when the top is taken away. Reader Carol is having a problem with aspens which she writes about in my post about tree stumps.

Pull out this sycamore before it takes over
It is tempting to retain a few seedlings or suckers that transform into pretty saplings and eventually a small tree. Woe betide a new garden owner who wrongly thinks his tree was deliberately planted. Most gardens are too small to accommodate forest trees. 
For me my main problems have been sycamore and birch which have appeared in their thousands. 

Holly and yew saplings suppressed for years under such as rhododendron suddenly become a problem
More insidious has been holly and yew in my cemetery gardens.Their seedlings often sneakily shelter under a plant canopy - even for years - and you suddenly find you have husky young saplings

As to yew, Peter Williams now has a very fine hedge from a hundred yew seedlings and tiny plants I once garnered for him from a cemetery garden.
I have a less pleasant memory of spraying off abundant yew seedlings with MCPA and glyphosate to eventually find my employer had a vision of growing a yew wood!

Self sown birch might become too big
I do admit to enjoying nature's providence by letting a few birches make saplings in my cemetery gardens. It takes a decade or so for them to reach their full glory. If they have become too big I just chop them down. 
I used to find that these chopped down trees suckered to make lovely multi-stemmed trees. Some birch trees in Bolton Percy cemetery are now on their third cycle!

None of the trees in Worsbrough cemetery were actually planted

Not all woody invaders are unwanted
Chemical control of woody weeds
I omit today the treatment of tree stumps. Where herbicides are concerned the principles however are very similar.
Their are many ways to actually kill woody weeds. Its just that you need to remember to do it.
So often I see tree seedlings left to become a real problem.

Myriads of seedlings
Under an old sycamore thousands of seedlings might suddenly appear in Spring. If it has been a cold Winter their necessary cold requirement has been satisfied and should it be a wet season they thrive. 
In a small garden you can just hoe them away. In a very small garden you can just hand weed. 
My own problem is where I manage large tracts of cemetery garden. My routine maintenance spray of 360g/litre glyphosate at 1 in 50 just does not work! (It might if the seedlings are still very small)
One solution might be to use glyphosate a little bit stronger, perhaps 1 in 40. In practice against woody weeds - and this includes such as brambles I use a mixture of glyphosate and MCPA each at 1 in 50. I would not do this anywhere near delicate plants, only in larger ‘open spaces’ or areas I deem ‘rough’. 

Ivy is a very difficult woody weed. Either live with it or (best) physically remove it, or use repeated herbicide applications to kill it
Unlike glyphosate, MCPA  remains active in the soil for a few weeks so don’t replant for a while after its use
I buy MCPA as commercial product Agritox and have written about it for example to control nettles in grassland. It can be used alone against woody weeds but beyond young seedlings is not very effective. 
In a lawn woody seedlings just mow out thank goodness!

If tree seedlings are allowed to remain into their second year you need a real brushwood killer to kill them. I have used the commercial product Grazon for this purpose. (I also use it for ‘difficult’ lawn weeds). It is quite brilliant but a bit pricy. 
I have appended these notes on chemical control for those of you with large scale problems. For most of us for woody weeds physical methods are better

Mechanical control
Your problems start when you allow woody weeds to pass the seedling stage and develop into saplings.
Saws, loppers  and spades will have a place in your armoury. My recent post, ‘a curious incident’, indicates my distain for actually digging saplings out - huge effort, sore back, broken spades and damaged plants.
Frequently if pruned tight to the ground woody saplings will be killed. Some will regenerate, especially those that are older and larger. Do it again later, they soon will be gone for a fraction of the effort of digging them out.
If you are timely smaller saplings can merely be pulled out. Don’t use you back. Strain with your arms and if their is no sign of movement give up and go for the secateurs!

Peter’s field - a story

Brenda’s son in France inherited a supposedly grass field full of thousands of four foot high four year old ash saplings. Well beyond my puny efforts with secateur and saw. Eventually he asked his local farmer who in less than an hour flailed them all down. I think Peter’s two grazing horses did the rest and as far as I know the ash has never returned (although on the neighbours property it is now a small wood).

Cathi's soay sheep ate all the tree seedlings but not the nettles 


  1. My sister has a tiny garden overhung by an ash tree. Not only is it a nuisance dropping ash keys everywhere many of which germinate in flower tubs etc but it also clogs up her gutters.

    Our best self seeded woody plant is a daphne brought in by a bird, Unfortunately though I think this year’s drought has seen it off.

    1. I too have seen daphne brought in by birds. I have often grown Daphne mezeureum from seed myself but am afraid this wonderful shrub just fades away in my soil
      Its hard to believe that the arboricultural world is very worried about ash dieback!

  2. We have problems with ash too enormous tree just next door I keep hoplng it wil get ash die back and be felled! Also had problems with Birch sprouting in hosta pot an conifers too all from a previous property we resided very suprised by confer seedlings. Nicest thing we had was a mountain ash but managed to kill it! Would not mind some Daphne seeding ( D.laureola I presume) they're native to woodland around here.
    We also have had Walnut seedlings and plethora of cotineaster and worst of all hazel they are a massive pest

    1. Don't tell anyone Matt but I am not over fond of ash either
      Thank you for your comprehensive comments - I could echo them all myself and failed to mention any. Thank you for enriching this post with your observations
      (note my comment about daphne to Sue)

  3. Don't forget Buckthorn and Mullberries!

    1. Thanks Jason, thats why my rhamnus keeps taking over the farm field
      I am puzzled about mulberries I have not experienced this do you have a personal story - or has anyone else?


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