Absolutely gutted

Does anyone know how rare it is to get the Lemon Tree? I'd also given up on mystery boxes after repeatedly getting white fences or other nearly useless items (did get the 30 donuts once, threw a massive block party in celebration). I'd love a Lemon Tree and if the chances are decent, I may throw some more donuts on the boxes (since that's the only way to get them now...and I'm a fool). But if I get one, I've decided I'm going throw the next Mardi Gras. Then I'll continue my habit of over-celebrating mediocre victories by chartering a trip to space (thanks Richard Branson) the next time I get a woman's number.