What's snow on the mountain? Never heard of it!

Euphoria or snow on the mountains.

Sorry never heard is this Bishop's Weed if so look at the link below

http://www.gardeningknowhow.com/ornamental/groundcover/snow-on-the-mountain/snow-on-the-mountain-plant.htm

Seed should be allowed to dry on any plant before harvesting and sowing. The trick is to catch the seed between it being dry and it falling off.

Euphorbia marginata--quite different from Bishop's Weed! Hidden among those topmost leaves, there should be little pea-sized, three-lobed capsules. When they start to turn yellow-brown, don rubber gloves--the sap can be irritating--pick the capsules, and put them in a paper bag. After a few days to a week, the capsules should split as they dry, and release the seeds. That way, you can choose where they come up next year.