Keep in mind when planting that Large Russian is thought of as hardy, so this plant will survive close to or on freezing temperatures. Ensure your soil has a ph of between 6.1 and 7.8 as Large Russian is a weakly acidic soil - weakly alkaline soil loving plant.
By our calculations, you should look at sowing Large Russian about 5 days after your last frost date.
Ensure that temperatures are mild and all chance of frost has passed before planting out, as Large Russian is a hardy plant.