Q.Parasitic Plants on Lilac and Forsythia
Both my lilac bush and the forsythia next to it last year developed what looked to be a parasitic plant bloom. The branches of both bushes lost their natural leaves and bloomed out with small clusters of odd looking leaves, almost like a small clump of grass where each natural leaf should have been. Approx. 1/4 of the lilac and 1/3 of the forsythia were affected and the small clumps stayed green all summer along with the natural leaves that were on the rest of the bush. No one that looked at it could tell me what was happening. The bushes are located on the northeast corner of my home but get sun at least 6 hours a day. We are on sand but have amended the soil over the years. Both were doing well and were 10+ years old when this happened. Any ideas? Thanks!

Certified GKH Gardening Expert
It sounds like they have a condition called witch's broom. There are a few things that can cause it. This article has more information on it: https://www.gardeningknowhow.com/ornamental/trees/tgen/witches-broom-disease.htm