Foxglove is a biennial plant that will reseed itself under the proper conditions. Collect and plant seeds on a yearly basis to guarantee the plant's return after the two growing cycles. The foxglove plant will produce tall spikes of bell-shaped flowers in USDA growing Zone 4 in the months of June and July during the second year of growth. The plant foliage remains low to the ground with the flower spikes reaching a height of 2 to 5 feet depending on the variety.
Choose a planting location that has a well-draining soil and full-sun to partial-shade conditions. Partial-shade conditions should be during the hot afternoon hours instead of morning.
Mix compost into the garden bed to increase the soil's nutrient value and moisture retention.
Plant the foxglove seeds directly into the garden soil in USDA growing Zone 4 after there is no danger of frost in the spring months through the midsummer. Place the seeds into the soil and cover lightly with one-eighth inch of soil. Space the plants 24 inches apart for best results.
Water newly planted seeds daily until seedlings begin to appear. Continue to water the seedlings weekly to keep the soil moist but not wet when rainfall levels are less than 1 inch per week. Monitor the soil moisture and water more frequently if necessary.
Fertilize the foxglove plants with an all-purpose fertilizer once the seedlings have become established plants. Fertilize mature plants on a monthly basis.
Apply a thin layer of compost around foxglove plants each spring to increase the nutrient value of the soil.
Apply a 2-inch layer of mulch on top of the compost around foxglove plants to assist with moisture retention and weed control.
Stake tall growing foxglove varieties to prevent drooping and flower damage.
Remove flower spikes after flowering is completed to encourage additional blooms. Do not remove flower spikes if you want to collect seeds.