Throughout the spring, donkey tail displays small, bright yellow flowers that eventually turn to seed and scatter throughout the garden, making way for new plants the following spring. Allow the plant to seed naturally or cut the seeds from the plant before they fall off and plant them where new plants are wanted. New plants that develop in unwanted areas can be dug up and moved to any sunny location in the garden or planted in pots.
New plants are easily developed using just the leaves of the donkey tail. Remove full leaves from the plant and place them in the ground or in pots in good potting soil. Keep the soil consistently moist but not waterlogged, provide plenty of light and the leaves will quickly root and grow into individual plants.
Use plant cuttings to develop new plants. Place a single stem over soil and keep it well-watered; the individual leaves will develop roots and grow into separate plants. Planting the stem base of the cutting in soil also will promote root growth on the stem. Donkey tail is a quick spreader in the garden; dividing plants and planting the separated pieces also will allow those plants to grow and seed in their new locations.
However propagated, young plants need the right care and conditions to ensure a good start and healthy growth. Grow donkey tail in full sun or bright lighting; low light or shade will cause the stems to grow long and leggy, and the leaves to be small or nonexistent. Drought-resistant, the young donkey tail plants should not be overwatered, but kept consistently moist until rooted. Established plants need minimal water. Wear gloves when handling donkey tail to avoid allergy issues some people experience with the plant.