Early spring or late fall are the best times to plant wildflowers. For spring planting, plant wildflower seeds after the last frost, when soil temperatures are regularly above 55 degrees. Planting early before excessive heat strikes will help your wildflowers establish strong roots before more stressful conditions arrive. Keep the soil moist until seeds are established, supplementing spring rainfall when necessary. For fall planting, timing is very important. In warmer climates, planting 4-6 weeks before the first frost allows your wildflowers to establish strong root systems before freezing temperatures hit. In northern climates with consistent cold in winter, it is best to wait until soil temperatures are below 55 degrees to maintain the seed dormancy and prevent the seeds from germinating until warmer weather returns.