Water runoff from your roof is most likely the culprit. If you have a gutter system installed, make sure that it has been cleaned thoroughly to allow the water to be routed away from your landscaping. D not forget to check the downspouts too. If you do not have gutters, this would be an invaluable asset to your home. Correctly installed gutters and downspouts can not only add beauty to your home, but will protect your home, the foundation, and will help save the landscaping.