Companion plants/flowers to plant with cold crops in NJ

I live in NJ(zone 7) and I will be planting cold crop in my garden in the next couple weeks(bok choy, beets, carrots, cauliflower, cabbage, brussels, collards, kale, leeks, swiss chard, onions). Last year was my first try at a garden and I failed to document my successes/failures/problems(I won't forget this year). Anyway, I don't remember there being many pest problems in the early spring months, however there may have been some problems with greens. Anyone have suggestions for compaion plants/flowers that I can plant March/April just to get an early jump on pest control? Marigolds worked great last year(100s of tomato worms and no damage to my tomatoes) but I don't think they can go in until May.