One of the limitations of blogging on Blogger is that as of now we don't have specific custom pages for things like an "About" page on your blog. Even if the option is now yet available there are a couple of things you can do to make your own custom pages.
Post Pages option
If you take a look at the navigation bar at the top of this blog you'll see that I've managed to create some custom pages for various information I want to highlight. This option is simple and can be achieved using the settings of your blog. Go to Settings and select yes where it asks you if you should enable post pages. What this does it make each post on your garden blog a specific page that you can use to create a custom page on your garden blog. This is the method I employed to create the pages you see in the navigation bar above. When you're composing your specific page click the Post Options link at the bottom of the window you're typing your post in. There you'll be able to remove the comments option from these specific posts. If you have an established blog date your specific pages to a date in the past and they won't show up as current entries on your blog.
If you've set up your blog with a custom domain your domain registrar may have given you a package that includes a small website option. For example you can create static pages such as about.yourgardenblog.com or contact.yourgardenblog.com page. If you don't want to pay for bandwidth or deal with setting up a small website you can try one of the many free options that are as simple as Blogger to set up and maintain. Google has a new product called Google Sites that you can use to set up a website or wiki to accompany your garden blog or create custom pages. I've also used this option to create the announcements page you see in the header.