Would someone be able to help me identify this weed? I first noticed it in my garden and lawn about two years ago, when some "foreign" soil was introduced into the back yard. It is spreading and I have found it infesting more soil. When I go to pull it, it launches seeds as soon as the plant is touched. It is the perfect organism that sows its seed when its life is endangered. The roots are relatively shallow so it is easy to pull, especially if I catch it early. Small white flowers are found on young plants; leggy branches with the seed launchers on mature plants.

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