The common globe amaranth is easy to grow from seed, although seedlings can also be purchased as bedding plants. Seeds can be sown directly into the garden after your last frost, or in seed trays indoors to give your plants a head start.Sowing seeds indoors: Sow seeds 6-8 weeks before your last frost, 6 mm deep in a seed tray. Once seedlings emerge in 2 weeks, they will need to be kept on a sunny windowsill. Seedlings will need at least 2 sets of true leaves before they can be planted in the garden, and should also be hardened off first.Sowing seeds in the garden: Wait until there is no more danger of frost and sow seeds in a sunny location in well-drained soil, 6 mm deep. Once seedlings reach 2.5 to 5 cm in height, thin so that they are around 25 cm apart.Planting in the garden: Choose a sunny location in your garden and plant on a cloudy day or in the evening, to prevent transplant shock. Dig a hole large enough for your plant's root ball, and then gently place your plant in. Fill in and firm the soil down, watering thoroughly afterwards. Applying a light mulch will help to retain moisture and prevent weeds. Leave around 18 to 30 cm between each plant.