What's a strobilus?

It's this!

Strobilus of Equisetum arvense - field horsetail

The reproductive structures of horsetails are called strobili (strobilus in the singular). They appear in spring before the branching stems and look interesting popping up in the garden. They aren't flowers, but perform essentially the same function - reproduction. They produce spores that are carried away by the wind to develop into new horsetail plants elsewhere.

If you ever get the chance to look at horsetail spores under a microscope, do it. They have little appendages called elatiors on them that react to moisture - if you breathe on them, they dance about. It's brilliant.

A profusion of Lunaria annua - honesty - flowers

The bright young leaves of Ulmus (elm - probably U. glabra - wych elm) expanding

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