Sure you can grow it! Like all other cucurbits, butternut squash is a warm season crop so starts just now appearing in garden centers and nurseries. Generally, starts do not get planted until both soil and nighttime air temperatures are warmer....after Mother's Day or around the first of June. OK to start seeds now and Hume, Burpee and Territorial all carry butternut squash varieties.

Or you can use plastic shelters to provide a warmer growing environment - at least initially.

Even in the warmer climate of Portland, butternut squash do not ripen until mid-September to early October--even the smaller, fewer-days-to-harvest varieties require patience.

An initial shelter may help--once blooming, the squash need to be visited by bees.

If you can get some squash to enlarge on your vines, trim off the remainder and late blooms, making the plant focus on the viable squash. The squash need to be fully sized by Labor Day or it will be too late. Expect considerable mildew on the foliage.

You don't have to have walls coming all the way down on all sides and wouldn't want to anyway, once the weather turns consistently sunny.