Lawns - Do I need to worry?

My neighbor has a tree that drops "whirlly birds" all over my lawn and I usually rake them up. When I took all the wood chips out of my kids' play area I put them under my deck. There must have been some of those in the chips cuz I have these little plants growing under there now. So my question is do I have to crawl under there and rip them all out or will they just die on their own?

Sorry if this is the wrong forum, wasn't sure where to put it.

Yes they may root in and grow. You should be able to use a steel rake and break 'em out that way. Or you could just spray 'em with Roundup or a brush killer product.

They are maple tree seeds.

Brush killer is the better choice as it covers the specific class that trees are in and roundup doesn't though as a seeding it would probably still kill them.

If the kids are still young, I'd be carefull spraying bark as it absorbs and holds the poison. Could you pull them as saplings, instead? Or you might try this, though it's for weeds:
Weed Killers (http://www.backyardgardeningtips.com/garden/weed-killers/) Be safe, G

Sounds as if it is Poplar. If so, they will pull up easily. They grow so fast, their trunk and leaves overpower their root system to hold them while young.