Five big 'uns
A burglar need not trouble himself to look for a build-up of post, curtains not being drawn, lights switched off of an evening, etc etc - he could simply take a stroll down the garden and if there are marrows where there ought to be courgettes, he'll know he's struck lucky and the householders are away.
Either that or the gardener has become obsessed with weaving and can't be bothered to harvest the veg (or cook it either).
Actually both these hypotheses are true in my case. I've just come back from my holiday.