The Winter Garden is a nice place for your plants to bloom even when it's cold outside. It was first released on March 25th, 2012 as a reward for raising St. Patty's Treasure. Anyone joining after St. Patrick's Day event 2012 need only raise 15 plants to adulthood in order to receive the Winter Garden. Just owning 15 adult plants doesn't count. The player must raise all 15 in their own game account. Everything else applies.
As soon as at least one Leprechaun in a player's garden grows up, the Post Pixie delivers a thank-you letter from the Leprechaun (who can now return to Ireland) and a parcel containing the key to the Winter Garden and four decorations (flowerpots): . After placing the flowerpots in your Winter Garden, you will get four spots for planting adult flowers. There is also a possibility to place the flowerpots in the The Atrium. The Winter Garden seems to offer room for future Decorations as well (at the moment there are as many as 10 decoration spots, but only 4 flowerpots).
You can always access your Winter Garden from My Garden page by clicking its little image . When you are in your Winter Garden, the garden image at the top or the link "to the center" beside the image takes you back to My Garden page.
Any adult plant from your collection below the Winter Garden can be placed in a flower container. Flowers can be removed back to your The Greenhouse by clicking the spade image . Flowerpots can be removed by clicking the tool shed image , but they must be empty in order to be removable. Placing and removing items has been described in detail in the article about the The Atrium.
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