If mixed planting must trim back, it will take over alyssum and even fight wave petunias. In several containers I also planted with Marigolds centered in a giant container, surrounded by 4 each of alyssum and double red's. The double reds were the first show off's performing excellently. But after twice weekly cutting the double reds back from the alyssum and occasionally out of the marigolds, the blooms are great. However by the end of July it has barely breached the rim of the container. The Alyssum has finally fought it's way to a beautiful bloom and it's breach over the side has at last occurred, just as the double reds greenery appears to be looking lighter, thinner, unattractive, as we'll as the dead heads are starting to cling numerously even with heavy misting in a windy location. I would not use in a mixed pot again. And would only use as a border well back from other plantings or as a solo plant.