Perhaps that is because whatever rose or roses the rugosa species was crossed with was not drought tolerant, and those/that rose's characteristics predominate. I have one rugosa that is absolutely not drought tolerant--Mme Georges Bruant. One parent is the tea Sombreuil. MGB's leaves wilt easily in the heat of summer here, as do the flowers (when she has any). On the other hand R. rugosa alba is tough as nails, and the Austin rugosa Wild Edric is one of the most drought tolerant roses I own. He laughs at blasting heat and is a water-sipper. I have him planted between R. californica 'Los Berros' and a mystery hybrid perpetual from Eurodesert. When Los Berros is showing signs of distress with leaves becoming wilty in the heat, Wild Edric looks fabulous. But I will give him some water when perking up Los Berros. However, I give Wild Edric significantly less. Both are within a year or so in age since I've had them (with Los Berros here longer). Wild Edric is grafted on multiflora while Los Berros is own root.

Schneezwerg is on my wantlist. Would have it already if there hadn't been a ban on shipping roses from Pickering in Canada this season to the US. This fall Pickering should be back shipping to the US, and I plan on getting Schneezwerg and probably a couple more rugosas. I would also like to get Schneezwerg's other parent, R. beggeriana, but I can't find it available from any nursery that can ship to me.

Melissa