Landscape Attributes. Allyson Mexican Heather is a evergreen shrub often grown as an annual, with an upright spreading habit of growth. Its average texture blends into the landscape, but can be balanced by one or two finer or coarser trees or shrubs for an effective composition. Allyson Mexican Heather | Calloway's Nursery Please note: You are currently browsing img garden design 62429 garden inspiration ideas that is 600x450px in size. This image is listed in mexican heather landscape ideas category. Allyson Mexican Heather Calloways Nursery, 600x450 in 122.74 KB.