No worries, those 50 shades of gray lichen may look like they are dominating and devouring your garden but they are harmless to plants. Lichen is a combo of algae and fungus often growing in moist or dark areas. You can use a gloved hand or brush to remove it from tree trunks or branches and a pressure washer of mild bleach solution on your roof and sidewalk. Products that kill algae on roofs also get rid of lichen. When summer arrives the problem should fade away. Keep growing, Marianne Binetti