How to distinguish Elderberry from Mountain Ash?

Question

Pictures of both plants look quite similar, it seems leaves and berries can look quite similar too when it is about the red Elderberry.
Pretty sure however that you know a lot of details about how to disnguish the plants from each other.
The reason I want to is that I have both plants in the area and want to pick the Elderberries but not mix that up with other berries, especially not mountain ash, of which the seeds are not healthy.

Thank you!

Answer 1

The Two shrublike trees can be easily distinguished in the summer by examining their leaves. The leaves of both trees are pinnately compound. Each leaf comes of the stem (twig) and is split into separate leaflets. The american mountain ash has 11 to 17 long, narrow, toothed long-pointed leaflets. There is one terminal leaflet and pairs of leaflet per leaf. The northern mointain ash is similar but the leaflets are less than three times as long as wide, and the leaf is somewhat whitened underneath.
The red elderberry also has pinnately compound leaves, but the leaflets number 5 to 7 . They are elliptic in shape and wider than then the mountain ash leaflet. The red elder has much coarser teeth along each leaflet. The ash teeth are very small. The elderberry is very similar to the red elderberry but has brownish pith. The red elderberry has large, purplish buds. The common elderberry has small brown or green buds. The mountain ash has red, gummy buds.
The fruits and flowers are substantially different from each other too.
Hope that helps.
Doc. Dan.

Answer 2

It would help if you were a little more specific about your location, or the scientific names of the plants. Here in California, red elderberry has 5-7 leaflets and mountain ash 9-13; but red elderberry is poisonous (at least the seeds are).
I find that aside from the number of leaflets, the elderberry leaflets are larger and lighter green, and have a distinctive smell. Plus the mountain ash berries are larger than elderberries.