Our soil here is on the acid side. There are many conflicting reports as to whether clematises prefer acid, alkaline or neutral soil, but from my first clematis planting in '92 I've used a chunk of cement in the hole (to hopefully get the soil more alkaline) and they grow fine. I do not get crazy with pH measurements and I do use the long needled pine (hurray for you collecting it) because it's just so easy to lift it up to add more manure/compost/food/Epsom salt drinks. I can't do that with other mulches.
Today I had to lift two Reiman clematises so the feet of the workers, who will be installing new deer fencing, wouldn't harm the clematis. It's just left of the garden gate that was installed in 2009, the same year I received the clem's, and the posts were set in cement. I was fascinated to see the roots of both clem's went to the cement - not to all the good rich soil (lots of compost there) around it.
