River Birch


Hi there,
our 4 year old river birch seems to have trouble leafing out this year. Some of the internal branches are missing some leaves so it looks a little threadbare. Could it be from my dogs peeing on it? Is there anything I can do to encourage leaf growth? the leaves are also a bright green colour this spring- is this normal?
Last year we sprayed it for caterpillars with Safer’s btk insecticide as well, not sure if that may have affected growth this year



With regards to your River Birch (Betula nigra), I am going to answer your questions in the order you asked them, see below.

  1. Dog urine is usually in the range of 5.5 – 7 on the pH scale which lets us know whether it is acid or alkaline.  If your dogs are in this range then they would be neutral to slightly acidic.  If you think otherwise, a pH test will clarify this.  The impact of dog urine around your particular tree, in the soil, should be fine as River Birch like slightly acidic to acidic soils.  That being said, if they are male dogs and urinate on the actual tree trunk bark, they may be causing more damage than you can see.  I would suggest you keep the dogs away from your tree area and mulching can help with this.
  2. River Birch, as the name suggests, grows naturally along stream banks, floodplains and forested wetlands so they do like to have a moister soil environment.  Although April seemed quite rainy, this spring has been particularly dry with not much in the way of rainfall so your tree may be thirsty.  So, giving it frequent thorough watering’s over the course of the next few weeks should help.  This is also a great time to fertilize your tree.  You can find many appropriate fertilizers in any good nursery – get one formulated for deciduous trees and follow the application instructions precisely.
  3. Having just had a peek at the River Birch growing in my own garden, it’s leaves are a light green colour which, from past observation, will darken as the season progresses and they mature.
  4. Lastly, to the dreaded LDD moth and the caterpillars that munch their way through the tree canopy with what seems like careless abandon.  There is no doubt this non-native pest has had an impact on all trees in infested areas over the last couple of years.  Many trees, after being defoliated, struggle to find the reserves to put out a second flush of leaves which puts them at a disadvantage the following year.  The best thing you can do this year is to purchase more Btk and be prepared to spray early and more than once.

If you feed, water, spray and keep your dogs away, your tree will have the best chance to not only survive but to thrive.  Hope this helps.