Definitely add your site to Google Webmaster Tools because it will show the exact terms your site is ranking for and the click through rate (the % of people who see you in search results and click through to your site).

You need to do keyword research and target every page and post to a specific keyword. When you write blog posts, use tags liberally and include keywords that people would use to search for that cannot be use in writing (like 'how grow tree' instead of 'how to grow a tree'). Link keywords in your site text to other pages on your site (especially on the home page). And blog consistently for at least 6-12 months, after which you can reduce your blogging schedule without negatively affecting your organic traffic (but don't stop blogging!).