Standard advice is to ignore bad behaviour so as not to reward them with attention, or say 'No, you must not do XYZ'. Problem is I don't want to ignore my son picking all the flowers in my garden - I work hard to get them - and saying no doesn't work.
I did a stupid thing today when said DS picked another flower. We'd just been to playgroup where he'd done a picture and he was quite attached to it on the way home. So when I saw he'd done that I picked up his picture from the floor (he'd dropped to attack the flowers) and ripped it up. I then told him that's how I feel when he picks my flowers. I have been (rightly) eaten up with guilt since it happened; it was such a stupid thing to do. Now when DS is cross, he's going to get all destructive like I did. I glued the picture back together on another piece of paper but it didn't really make up for it.
Please send me advice, remonstrations and anything else you care to...