Can I bring evergreen lawn feed in my hand luggage from Uk to Europe?

Not sure check DEFRA website.

Probably not as its flammable and 'toxic' if incorectly used and therefore quite likely banned in flight!

That would be a NO! you are likely to get arrested as carrying something through that could be used to create a bomb! Why would you want to do so in any case?

You could always ring Customs and ask but I think you already have your answer.