Don't do it
VALID's first ever publication was a Summer Branch Drop (SBD) Guide, way back in 2018.
The reason we got this guide out first was, in the UK we had a stinking hot dry spell in July 2018. It triggered many enquiries from Arborists and Duty Holders concerned the risk from SBD was something they needed to manage urgently. Otherwise they could end up in court. That unless they hastily erected signs, fenced trees off, or pruned them, they'd be liable if a death or injury happened.
Keen to bring some common sense to managing the risk from SBD. We rolled up our sleeves, did the research, and got the guide out within a couple of weeks.
5 years on, and we've updated our Summer Branch Drop Guide to v9. Mainly to include a section about why it's unwise to put up warning signs about Summer Branch Drop. We've had enough people ask whether we can make this point clearer and explain it. So we did.
Don't put up signs like this
As ever with our publications, we've waived copyright on the SBD Guide and released it under a creative commons licence. Anyone is free to use it.
If your trees have no history of SBD, warning signs are unnecessary because the risk is Acceptable.
If you have a tree that has a history of SBD, and the risk is not Acceptable or Tolerable, warning signs are not an effective way to manage the risk.