Tulip bulbs are not coming up
In the fall of 2012 we planted 750 tulip bulbs in beds around our foundation and around a tree in the front yard. Last spring (2013) it seemed as though every bulb came up and bloomed - the display was beautiful.
After the tulip blooms were spent we cut them off, leaving the foliage to deteriorate on it's own. After the leaves had died off we planted bedding plants in two of the beds and Zinnia seeds in the third. The Zinnias came up quickly and bloomed prolifically all summer long. After the first frost we removed the Zinnias and bedding plants for the winter.
Fast forward to this spring - In two of the beds only about half of the tulip bulbs have come up and in the bed that had the Zinnias last summer, not one single bulb has come back. We are perplexed as to what we did wrong. The Zinnia bed receives full sun almost all day while the other two receive varying degrees of sunlight for parts of the day.
We certainly don't want to make the same mistake again. Any ideas on what went wrong or what we can do better in the future are greatly appreciated.