That's one of the higher levels, so once your power grows you'll be able to eventually. The most you can do now is help plants grow faster. It helps to do that around the city.

[like in the park, or here in the garden.] Constant practice helps too. Soon enough.. [he holds his hand over the plant Lucas had grew, concentrating and snot a second after it begins to grow double its' size.] Well, you'll be able to do a lot more.