I have had some plants that looked very much like that specimen . Although mine were green I also had some with pink leaves as well . I cant tell you for certain but I think it is cardinialis Im not sure of the diffrent types of this plant or the spelling being correct sory .But I can tell you if it is cardinialis it will not do well in gravel , and is usually in small clusters . Also this is a medium growin plant it will not get tall but will ''thickin'' or bush up kinda like a shrub or grass tends to do .
Sory I cant be more help , I will however keep looking I love plants especially wild types and diffrent specs.
Hope this helped some .