I'm in eastern Colorado, USA, Köppen BSk. We've planted 200+ trees and shrubs in the last 2 years. Two of the three areas are drip irrigated, but the newest area of 70 is not. I water once per week, about 2 gallons per plant, dumped at the base of the plant all at once in very sandy soil. It is a hard life here, with hot, windy summers and cold, dry winters. We have had about a 15-20% mortality rate. If they can't survive on that amount of water, they can't live here. They are all tough, supposedly deep rooted plants. Siberian pea shrub, manchurian apricot, elm, honeylocust, golden currant, hackberry, lilac, chokecherry, burr oak, buffaloberry. They all are mulched with wood chips in a small circle around the base. Without at least some irrigation (they say 3 years) and mulch, nothing but Russian thistle, black eyed susans, and native grasses would grow. The summer rains haven't made it here yet, so I've not seen any natural moisture below the mulch this summer.