First of all, my bid should be considered directional only, based on your budget. You don't say if you need blog articles, magazine or other print articles, brochures, social media posts or even emails. It would be good to know what the final product is and how many articles (or whatever) you need.
My billing rate is $50/hour, and I estimate that -- even with considerable research -- I can provide you with articles of 500-750 words for $250 per article. I'm an excellent researcher, and I understand when you say the candidate you choose has to be able to analyze sources, organize his or her thoughts and write compelling pieces. During my 40-year career in marketing communications, I wrote a wide variety of materials -- print pieces as well as online content -- on a broad range of topics. No, I'm not a landscape/garden expert ... but I think you'd be better served by someone who, like me, would need to research the topic, learn something new and then explain it to your readers. Let me write one piece for you as a test and you decide!
Since I've been working with Freelancer.com, I've won 14 contests and earned additional work -- primarily blog articles and website content -- from four of those employers. All of them found me easy to work with, able to understand and meet their needs, and capable of meeting deadlines. I write clearly, succinctly and in a persuasive manner, and I'm a native English speaker. Thank you for your consideration. I look forward to hearing from you.