I have uploaded my sitemap to the server root folder. Do I need to submit it to Google Search Console (formerly Webmaster Tools)?
If you want Google to report on your XML sitemap and inform you of any errors and index status of the pages within the sitemap then yes, you need to submit it to Google Search Console (formerly Google Webmaster Tools). One of the points stated in the Search Console Help document under "Why my sitemap isn't listed" clarifies this:
Only sitemaps submitted using this report are listed; sitemaps submitted using google.com/ping or robots.txt are not on the report, even if Google can find and use them.
However, you don't necessarily need to submit your sitemap to GSC for Google to simply pick it up and use it. You could include a
Sitemap directive in your
robots.txt file. For example:
This will also inform other search engines, not just Google. However, this alone might not be quite as immediate as submitting your sitemap in GSC as it is dependent on your
robots.txt file being crawled. And, as mentioned, unless you do actually submit to GSC then it won't be acknowledged in GSC and you won't benefit from Google's sitemap reports.
Search engines probably won't pick up the sitemap if it's simply upload it to your document root. XML sitemap file(s) can be called anything, so without being told, search engines don't necessarily know what to look for. If you called it
sitemap.xml then you might expect search engines to be able to pick it up, however, I see no requests for
sitemap.xml in my access logs (for sites that don't contain an XML sitemap), so this strongly suggests they don't.
When your sitemap changes, you will need to resubmit (or inform Google) that your sitemap has changed. This can be done automatically by pinging Google (a GET request), without having to manually resubmit the sitemap. For more information, see Google's help page on submitting sitemaps.