Autumn planting help plants to establish quickly before the onset of winter. At this time of year soil is still warm enough to promote root growth yet is unlikely to dry out. Spring planting is especially good for late-flowering perennials. Also in cold areas, perennials that are not entirely hardy or dislike wet conditions, are best planted in spring. This will ensure that they will be fully established before their first winter.
Bare-root perennials should generally be planted in spring or autumn. Few perennials, like hostas, may be successfully transplanted during the growing season.
Prepare the ground well before planting to offer your plants a good start, then plant perennials in prepared ground taking care to position them at the right depth. For example, the ones that are prone to rotting at the base will benefit from a planting proud of the soil so that the excess water may drain away.
When you are planting perennials that were grown in containers, water them thoroughly in the night before planting, so that the root ball is well soaked with water. Dig a planting hole and then remove the plants from their containers. Taking care to not damage the roots, carefully loosen the sides and the base of the root ball by teasing out the roots with your fingers or a hand fork. This will help plants to establish quicker and is helpful especially for the root-bound plants. Place the plants at the right depth in the prepared hole, backfill with soil and firm. Loosen the surface of the soil with a hand fork then water in thoroughly.
Most perennials are best planted in the ground at the same soil level as they were in their pots, but there are a number of them that grow better if they are planted deeper or higher than they were in their pots. The planting depth depends on their individual requirements. Some will prefer a raised and well-drained site while others will thrive in deeper and moist conditions.
According to their requirements of planting depth, you can consider 4 types of plantings. Ground-level planting – perennials are planted so that the crown of the plant is level with the surrounding soil. Raised planting – this planting is suitable for plants that are prone to rot at their base and for plants with variegated leaves that tend to revert. These plants will do better if planted with their crowns slightly above the ground. Shallow planting – this is for perennials that require a moist environment. They should be planted with their crowns about 2.5 cm below ground level. And the last type, deep-planting – for perennials with tuberous root systems. They are planted so their crowns are about 10 cm below the soil surface.
For the bare-root plants, the planting should be done as soon as possible after you purchase them. This way you will prevent dehydration and the plants will have more chances to grow well. Prepare the planting hole as for container-grown plants. Place the plant into the hole spreading out its roots evenly. Add soil into the hole, working in soil between the roots, then water well.
Another way to add perennials into your garden is to plant seedlings. You can buy them or you can use the ones you already have into your garden. Many perennials regularly produce self-sown seedlings that you can lift and move to another location in your garden or to a nursery bed. Prepare planting holes suitable for the seedlings and space them evenly and far enough to allow room for the plants to develop. Then lift gently each seedling with a trowel taking care to retain as much soil around the roots as possible. Plant them immediately into the prepared holes. Firm them in well and water thoroughly. In sunny weather protect the plants from direct sun by shading them. Water them regularly until they are established.