Beware the Helicopters: A Mast Year and the Risk of Sycamore Poisoning

If you’ve been out and about this autumn, you’ve probably noticed the trees showing off. 2025 has been what’s known as a mast year, basically, nature’s version of a bumper crop. Trees everywhere are laden with fruit, berries, and seeds.

Lovely for wildlife… not so lovely for horse owners.

Because with a mast year comes a whole lot of sycamore seeds, or as we like to call them, those mischievous little “helicopters” that seem to spin their way into every corner of the field.

And thanks to Storm Amy, those pesky helicopters haven’t just landed nearby, they’ve gone global. Well, at least as far as the next paddock.

The Risk: Atypical Myopathy (Sycamore Poisoning)

Here’s the serious bit. Atypical Myopathy, more commonly known as Sycamore Poisoning, can occur when horses ingest sycamore seeds or seedlings.

The tricky part? Not all seeds or seedlings are toxic, but we can’t tell which are which. It’s like a very high-stakes game of chance that no horse should have to play.

Normally, horses won’t go out of their way to munch on seeds or saplings. But if grazing is sparse, they might nibble out of curiosity or hunger, and that’s where the danger lies.

What You Can Do

A little prevention goes a long way when it comes to protecting your horses:

• Pick up seedlings whenever you spot them, a bit tedious, yes, but worth it.

• Section off any areas that look like a sycamore seed carpet (you’ll know it when you see it).

• Stay extra vigilant in October, March, and April, those are the key months when seeds and seedlings pose the highest risk.

• Manage grazing effectively, this will prevent hunger and curiosity getting the better of your horse and dissuade them from trying a nibble...they'd rather eat grass! Providing soaked hay, or slowly strip grazing can be enough to steer them away from those seeds.

  
  

Know the Signs: It’s a Veterinary Emergency

If you even suspect Sycamore Poisoning, call your vet immediately. Time is absolutely critical.

Watch for these symptoms:

• Weakness or lethargy

• “Tucked up” appearance

• Reluctance to move or shuffling gait

• Depression, muscle tremors, or sweating

• Rapid breathing

• Signs of choke

It’s scary stuff, but awareness makes all the difference.

Final Word

In short, those pretty spinning seeds aren’t just a nuisance for your mower. Keep an eye out, keep the fields clear, and you’ll be doing your horses (and your peace of mind) a big favour.