Gather thistles, expect prickles.

The saying presents an ordinary chain of cause and effect: choosing or collecting something thorny makes an unpleasant result foreseeable rather than surprising.

It warns that harmful, troublesome, or ill-chosen actions and associations can bring corresponding difficulties. Pleasant outcomes should not be expected from conditions that naturally produce pain or trouble.

Use it to comment on an unwelcome result that follows predictably from what someone chose, encouraged, or put into motion, especially when that result should have been anticipated.