These crawls are part of an effort to archive pages as they are created and archive the pages that they refer to. That way, as the pages that are referenced are changed or taken from the web, a link to the version that was live when the page was written will be preserved.
Then the Internet Archive hopes that references to these archived pages will be put in place of a link that would be otherwise be broken, or a companion link to allow people to see what was originally intended by a page's authors.
The Ask Alys series ceased at the end of June 2017. Visit the RHS Advice website, which is a good resource for gardening queries: https://www.rhs.org.uk/advice/advice-search.
Ask Alys: can I grow blueberries without peat?