"Is it difficult to tell the poisonous ones from the safe? " No since they are all poisonous. The roots are very bad. But the leaves and stems are fairly poisonous too, they won't kill you, but you could be hospitalized. The berries also have poison, but in low doses. Easily removed if cooked. This goes for all elderberries. The red ones are said to be worse, but they are not. From Wiki: The ripe, cooked berries (pulp and skin) of most species of Sambucus are edible.[13][14] However, most uncooked berries and other parts of plants from this genus are poisonous. Sambucus nigra is the only variety considered to be non-toxic, but it is still recommended that its berries be cooked slightly for culinary purposes.[13] The leaves, twigs, branches, seeds and roots of Sambucus plants can contain a cyanide-inducing glycoside (a glycoside which gives rise to cyanide as the metabolism processes it). Ingesting a sufficient quantity of cyanide-inducing glycosides can cause a toxic build up of cyanide in the body. In 1984, a group of twenty-five people were sickened, apparently by elderberry juice pressed from fresh, uncooked Sambucus mexicana berries, leaves and stems. However, all twenty-five recovered quickly, including one individual who was hospitalized after drinking five glasses.[15] Such reported incidents are rare This post was edited by Drew51 on Sun, Mar 30, 14 at 23:13

Cut & paste from a previous post I made... Chances are you have a Common elderberry (Sambucus nigra subsp. canadensis), which is native to the Eastern U.S. and grows as a bush to 6-8 feet. The European elderberry, Sambucus nigra, is more upright/tree-like, but about the same height. These both have dark purple berries. There is also Sambucus nigra subsp. cerulea, which has blue berries and is native to the West -- I've never seen one. There is also a completely different species, Sambucus racemosa, that has poisonous red berries (not purple or blue) that are NOT edible due to higher levels of cyanide (not sure if OK after cooking). For common elderberries, fruit quality depends on cultivar, although even the "ornamental" cultivars produce usable fruit. It's recommended to cook them due to cyanide content -- the toxicity is low, but eating the raw fruit can cause nausea (how much it takes varies person to person). Cooked berries are safe and make great jelly, syrup, and wine. The flower clusters can be fried. Here is a link that might be useful: CA Posion Control Report (Sambucus mexicana)

You'll need to purchase or start plants from cuttings if you wish to get what you see :) True patent name is Sambucus nigra 'Eva'..."Black Lace" is only the trademark name. I have the common species Sambucus nigra ssp. cuerulea (Aka S. mexicana)...Blue Elderberry if you want to try some seeds for this one. Berries are edible and used in jams, pies, etc. Let me know at la_raspberry@yahoo.com

yes i have seen this often with elderberry. even with well establishes patches with multiple plants, some of the berries will be great and some just dont quite make it. they take quite a while to get fully established before they produce a lot of flowers and berries. often they grow in huge patches with huge plants, you may want to add a couple of others of a similar variety to get better berries. and be patient, at least in my experience these take a couple of years to really get into their groove.