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I have a lilac bush which this year did not seem to come in as full as the past couple of years. In addition, I see some of the branches have these spiny growths on them. Does anyone know what that is?enter image description here

JoeMcG
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Well, that's extraordinary - the growths are typical of galls, usually caused by gall wasps. These are the culprits that cause the gall known as Robin's Pincushion on roses (https://www.wildlifetrusts.org/wildlife-explorer/galls/robins-pincushion), oak apples on oak trees, but I've never seen nor heard of any particular gall wasp that does this on Lilac, nor seen anything like these growths on Lilac either. I might be completely wrong - see what other answers you get, but some information on galls and their causes here https://www.kqed.org/science/23927/what-gall-the-crazy-cribs-of-parasitic-wasps.

If you don't get another more definite answer, if you have a local agricultural extension service (I think that's what they're called, I'm in the UK so these services are only something I've heard mentioned on here), ask them. I'd be fascinated to hear what they say...

Bamboo
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Joe, this is not a Lilac, grins. I am pretty sure this is a Witch Hazel: Hamamelis virginiana. Wonderful large shrub small tree!!

Witch Hazel

It is common to have different shrubs/trees grow in the same spot. I think this is a wimpy witch hazel integrated with the lilac shrub.

Very interesting, dying to see how this turns out! Thanks, Joe!

Do the leaves look familiar?

stormy
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  • it's definitely lilac, it has already bloomed out! And that's why I'm confused by it. It's like half of the branches have this going on, and the rest are what I'd expect from a lilac bush. – JoeMcG Jul 18 '19 at 21:59
  • Please send a picture of the leaves of the entire plant. Bamboo could be right as she most certainly seems to be...that there are galls producing these weird flowers that look just like Hamamelis. I hate it when she is always right!! arghhh! grins!! – stormy Jul 19 '19 at 01:17
  • This could easily be TWO plants, not just a lilac. Follow the branches of those witch hazel looking flowers DOWN to the ground. Do they have their very own trunks coming out of the ground separate from the Lilac? Send a picture of the entire plant (s), a picture of the trunks coming out of the soil and a picture of the LEAVES, even buds. – stormy Jul 25 '19 at 19:37
  • Possibly Crown gall? Agrobacterium tumefaciens (updated scientific name Rhizobium radiobacter) https://en.wikipedia.org/wiki/Agrobacterium_tumefaciens -Bit of a scientific tiff there. It does hit Lilac: https://www.fluvannamg.org/crown-gall/ – Wayfaring Stranger Aug 04 '19 at 00:13