Why is my new wordpress site so slow?

My new wordpress site's been optimized by limiting image sizes and other files and on gtmetrix is shows 97% yet after I had someone optimize the site, it doesn't seem a bit faster. Yet the speed score skyrocketed from 52% to 97%. Is it fast enough or is it me thinking it's slow? http://www.buylandscapingplants.com

PageSpeed Score
(97%)
YSlow Score
(87%)
Page Details
Page Load Time
4.6s
Total Page Size
737KB
Requests
29