We have this well made rain barrel operational for a few years now and leave it out in the cold Virignia winters (drained).  We built an even platform for it so it doesn't sit on the ground and is high enough so I can place a watering can under the spigot.  Didn't have success using a planter in the top part of the rain barrel - just wasn't effective for us - mostly because the plant was water logged when the barrel was full.  We also use mosquito dunks in the water and corks in the top of the barrel, so if any bees land for a drink of water they can use the corks as flotation devices to get out.