During normal play of the game eventually a beggar will start coming around to your garden (he has crazy purple hair).
Note: From MathGuy42
, a possible requirement is having your garden worth 25K before he will appear. Contradicting this is redjarman
, as Ivor showed up for him at 16,886 at Level 13. Its possible this may just be random or time based.
Give him 1,000 coins and this will turn him into Ivor and he will open up a new shop, where you can buy the best watering cans, shovel upgrades, seeds, and fertilizer, as well as popping the achievement for you. Definitely worth the investment.