This is in the Pacific Northwest? It was a mild winter here, without any additional information nobody can say what might have happened to your plants.

We live on South Whidbey. No other plants in proximity to these plants are are affected and these 2 plants are in totally separate areas of the quite large garden.

I seriously doubt it anything to do with winter cold......other established paperbarks in the area are doing fine. I've not known Acer griseum to fall prey to a sudden attack of Verticillium wilt as readily as say Acer palmatum but any maple species is susceptible.

As to the other marginals plants, cold damage is a possibility. We did dip down pretty far in November for several days. But I grow several pitts and a grevillea myself in containers that winter out on a south facing, beach front deck and they came through the winter completely unblemished. Including Pittosporum tenuifolium 'Silver Sheen', which is at best only marginally hardy for this area.

I did lose a large Digiplexis but I'm not all that surprised. I was very leery of its hardiness in this area to begin with.

Paperbark maple would never be tender here, unless we got an aberrant much, much colder winter than normal. So something else happened, probably in the soil environment. If this is or has recently been a wooded lot - particularly with stumps - you might want to check the carcasses for honey fungus. If there was a change in drainage patterns, that might do it also.

Otherwise all I can think of is an irate neighbor or other perpetrator dumping herbicide on the two specimens.

My daughter lost a Japanese maple because a neighbor sprayed herbicide on a windy day.

When that happens in my yard it is the result of gopher eating all the roots. Have lost many plants to gophers, some of them full grown, 7' tall rhododendrons.

Thank you all for your suggestions. Unfortunately none of the theories fit the picture. No change in drainage, no gophers, no sign of honey fungus and not near neighbors for herbicide spray. I guess it will remain one of those heartbreaking garden mysteries!