If you've never ridden in the American Southwest, you might never have encountered "Tribulus terrestris" - the dreaded "goat-head thorn", but for those of us who have to ride where they live, Summer and Fall can sometimes seem like an endless parade of flat tires - all because of this plant which looks like a medieval torture device.
Any bike ridden off-road can be victimized, which includes your cyclocross or gravel bike.
Goat-heads look like a tiny ball with spikes coming out of it, about 1/4 to 1/2" in diameter. The spikes are pointy and strong enough to puncture even the thickest bicycle inner tubes.
They commonly fall on un-landscaped areas, like the side of the road, or in vacant lots. They are less likely to occur in high-traffic areas, so stay on the trail or roads. It's a good practice to take a look at your tire tread during breaks, if you pick up any goat-heads you can try to avoid that area on the future.
It might be impossible to avoid the goat-head punctures entirely, but you can slow them down: