Keep in mind when planting that Intermediate Mixed is thought of as very hardy, so this plant will tend to survive through freezing conditions. Intermediate Mixed requires a loamy soil with a ph of 6.0 - 7.0 - it grows best in weakly acidic soil to neutral soil.
By our calculations, you should look at sowing Intermediate Mixed about 56 days before your last frost date.
Ensure that temperatures are mild and all chance of frost has passed before planting out, as Intermediate Mixed is a very hardy plant.