They only cross with other butternut type squash (C.moschata) No worry about cukes melons or C. pepo squash.

Thanks. I am trying to use more and more heirloom seeds and was delighted to find these and Malibu pole beans. I grow a couple of heirloom tomatoes and those three can just about get me through the year. I grow other things, but would be lost without these three.

as a general rule of thumb squash type plants such as cukes melons gourds summer and winter squash will only cross within the same species, very little cross pollination at the genus level and none at all within the family. i have seen anecdotal evidence to the contray where somone has said on a VERY rare occasion interfamilial crosses happen but I can not attest to truth of that statment. There are actual sudies that I have read, one from Purdue and the other from a group down in Mexico, that suggest some level of compatability between species of winter and summer squash but I do not believe the rate of cross pollination was high. As far as tomatoes go I would be a tad concerned as every single tomato cultivar is the same species and therefore 100% compatable with each other. However, being a perfect flower they are self fertile increasing the chance that pollen is moved from the anther to the stigma within the same flower. Beans I wouldnt worry about at all since all P. vulgaris cultivars and most others as well, are self pollinating and therefore neither reqire nor attract outside pollinators such as insects(the anthers and stigma actually touch one another in the flower so that when pollen is produced it is directly shed from one to the other, often before the flower ever fully matures). Inadvertent crosses between beans and peas i think is a rare occurence. However.some beans, such as fava and soy I believe do actually open and are much more receptive to insect pollination than P. vulgaris cultivars.