I've seen a weed on a roadside in Malta that did that. It was squirting cucumber - http://en.wikipedia.org/wiki/Ecballium_elaterium but I'd have thought that it wouldn't be warm enough in the Netherlands for it to grow.

It sounds like a plant I was given many years ago but I can't remember what it was called. It grew very tall (about 5-6') and when you walked past it, it threw all these seeds at you. It gave me the willies so I dug it out, but not before it had started to take over the whole garden, it was even growing in the lawn! I reckon it's an invasive weed with a mind of it's own and someone had a good laugh giving it to me as a flowering plant.

The very tall one sounds a bit like Himalayan Balsam and that is an invasive weed, and very troublesome. Its seed capsules burst and hurl missiles.
The squirting cucumber I saw in Malta was just a couple of inches high, but it was growing on rubble.

Can you give us any more info about the plant in your garden Stacemonst? Ab photo and an indication of the size would be good.