Reply Outdoor spring planting in Rhode Island should start after April 19 the average time of year the final spring freeze occurs, according to the Old Farmer’s Almanac, which also sets optimum times for planting garden favorites like corn and potatoes. (Liana Messina/Patch) NEWPORT, RI — The right time to start planting seeds outside varies by year, and even more so by region. But an Old Farmer's Almanac tool can help gardeners in Rhode Island plan ahead by finding the typical date of the final spring frost. Rhode Island gardeners should be in good shape to plant outdoor seedlings, since the last frost date was projected to be April 19. That kicked off a 182-day planting season, ahead of the expected first frost Oct. 19.