A field on the edge of Point Reyes Station holds the Porsches of the pumpkin world: “Jack O’Lantern” cultivars grown under Arron Wilder’s vigilant care. Planted last May in soil rich in phosphorus and potassium, the dime-sized seeds grew into fruits that weigh an average of 25 pounds. Here’s his strategy: Plant seeds, not seedlings, because tap roots dislike disturbance. Bury the seeds, on their flat edge, in an inch of soil, so they’re hidden…