I always wondered how long it would take for the willow whips to develop roots. As an experiment I popped a few 1ft sections into the pile of grass clippings in the garden on 23rd December 2017. Exactly 4 months later (23rd April 2018) I removed them and you can see clearly that several white roots have developed. There is also good leaf growth on the top of the stem. As they were only sitting in the grass clippings, it was easy to remove them without damage.
