I want to add trees into my environment using speed tree and wanted to know when i will be able to do it?
I have asked the same question while ago:
https://rocket.unrealengine.com/questions/4409/speedtree-integration.html
Short answer, it will be in Rocket, when integration will be good enough.
Maybe you mean this: http://www.speedtree.com/ue4.php , perhaps this comes pre-integrated on Roket later in newer builds with simplygon (or a public version)