Ah, that's an easy one-- they're from the demolition set from guatla at MTS: http://www.modthesims.info/download.php?t=350615

Their house was doubly unlucky in the transfer. Not only did the stay things shrub not work, but when I demolished the other house to shrink the lot, there was some invisible something or other that I couldn't find so I couldn't use LotAdjuster at all and had to rebuild from scratch. It didn't take long, but still. Annoying!