"See, they're not too bright ...The moment they know the de-gnoming's going on they storm up to have a look. You'd think they'd have learned by now just to stay put."
-- George Weasley (CS3)
Wizarding gardens have to be routinely “de-gnomed” or the gnarly little potato-head creatures will take over. Fantastic beast expert Newt Scamander wrote that gnomes should be caught and swung around in the air, then tossed over a fence or wall (FB).
Before de-gnoming the garden at the Burrow, Ron explained to Harry that making the gnomes dizzy keeps them from finding their way back to their old holes in the ground. But Harry noticed the gnomes returned almost immediately: "In the field far below he could see a gang of gnomes sneaking one by one back through the Weasleys' hedge" (CS3).
When Harry was bitten by a gnome and couldn't shake the creature off his finger, he managed to toss it 50 feet (CS3).
Fred Weasley was bitten on the ankle as he pulled carrots, so he grabbed the gnome and used it as a Christmas angel on top of the tree: "Stupefied, painted gold, stuffed into a miniature tutu and with small wings glued to its back, it glowered down at them all, the ugliest angel Harry had ever seen, with a large bald head like a potato and rather hairy feet" (HBP16).
Luna Lovegood and her father Xenophilius thought the Weasleys had a "glorius infestation" of Gnomes, or as they called them, Gernumblies (DH8).
Molly Weasley consulted Gilderoy Lockhart's book Guide to Household Pests when it was time to de-gnome the garden, but she never got a chance to tell the boys what his method was (CS3)