I have two 15 foot maples (2-inch diameter trunk) in our front yard. They shot up with quick growth last year, which was very impressive.
Now, with the recent rains on their thick foliage, they are sagging to an extreme degree. One tree, to the west of the driveway, has its lead trunk bending over at a 90 degree angle — it is now parallel to the ground, no longer pointing vertically.
Why can’t my trees support themselves? Where is their strength? Are they in danger of breaking? Vertical growth is the goal here, not stooping, drooping, sagging maples.
Should I prune them, or tie them up, or let them droop?
From your description it sounds like your trees could benefit from some pruning and/or staking. In general the former option is better than the latter. If you find that, after pruning, your trees still droop, you will most likely want to stake them. The goal with pruning is to slowly train the tree so that its shape fits your needs and the tree’s structure is sound. Below are some websites that will help you prune and/or stake your trees. The last two sites address in detail the issue of young trees.
The City of Seattle offers general tree care information that may be useful, as well as a page on young tree care.
The International Society of Arboriculture (ISA) has a succinct page about how to prune a young tree.
The ISA also has a section on how to plant a tree. Scroll down to find a diagram that shows how to stake a tree.
The National Arbor Day Foundation’s Nine Things to Know About Trees contains some pruning information as well.
A Grounds Maintenance Magazine column (now archived) by Michael W. Dougherty of Tree Management Co. addresses the specific needs of young trees.
Lastly, the Urban Tree Foundation’s Pruning page shows how to shape a young tree in order to strengthen its structure.