This has been growing in my yard for years and I have no idea what species it is.

This is only a guess:
Air Plant (Tillandsia abdita)

I found something similar but can't find anything on the pages .. Sitio design is mentioned, it's in Austin.

https://www.google.co.uk/searc...

I wondered if it's a hardy Dyckia?

A photo named Aechmea 'Burgundy' looks like yours ..

https://www.google.co.uk/searc...

Maybe?

https://www.google.co.uk/searc...

It doesn't look to have the spiny margins like most Dyckia I've seen but maybe there are some that are spineless? It reminds me of Aechmea recurvata var. benrathii.

This shows A. recurvata var. benrathii with green leaves: http://www.worldwideexoticsnur... but many Aechmea leaves turn darker in color with high light conditions. These two links show darker forms:

http://fcbs.org/cgi-bin/dbman/...

http://fcbs.org/cgi-bin/dbman/...

Horntoad said:This has been growing in my yard for years and I have no idea what species it is.

I was researching a different bromeliad and stumbled on this thread. Hope you don't mind it being revived.

I believe what you have is one of the Cryptbergias. They take on a reddish hue and clump freely.

Cryptbergia (XBiltanthus 'Red Burst')