Do you use the real Memorial Day, May 30, or the federal holiday which is the Monday before and can be a week sooner?

Depending on when you can plant, (first of April) and the weather between those should be good, especially peas, or maybe vetch, or both.

Allen 11: white clover is a good one for colder climates. Just chop it up and mix it with the topsoil before you want to plant. Ideally you would need to do this 30 days before planting so its propensity to kill off other plants would be dissipated. A beter idea yet is to plant cereal rye at the end of November and turn it under 30 days before planting in the spring. But you should only follow rye with large-seeded crops like peas or beans, or with well-established transplants like tomatoes -- because they are able to withstand rye's strong kill-competitors feature. Regards, Peter.