A perennial is defined as a plant that lives for more than two years, typically regrowing from the root structure each spring after the above-ground foliage dies back in winter. These plants offer longevity and consistent returns to the garden, distinguishing them from annuals that complete their life cycle in a single season. The simple answer to planting perennials in summer is yes, but it is not the ideal season and requires a substantial commitment to extra care compared to spring or autumn planting. Success hinges entirely on mitigating the extreme stresses of the season, requiring close attention to both the transplanting process and the maintenance schedule afterward.
Why Summer Planting is Challenging
Summer heat creates an intense struggle for newly planted perennials due to the accelerated rate of water loss. High ambient temperatures cause moisture to evaporate rapidly from the soil, depriving the roots of necessary water. The plant’s leaves also lose water quickly through transpiration, which can lead to rapid wilting if the roots cannot supply replacement moisture fast enough.
Newly transplanted perennials face a high risk of transplant shock, where the root system is temporarily unable to absorb sufficient water. Instead of focusing energy on developing new feeder roots, the plant is forced to prioritize survival and cope with heat stress. This stress means the plant will not establish itself quickly, leaving it highly vulnerable during its first few weeks in the ground. The perennial’s energy budget is focused on maintaining existing tissue rather than generating the new root growth necessary for long-term establishment.
Essential Pre-Planting and Transplant Techniques
Successful summer planting begins with selecting healthy, well-hydrated plants that are not showing signs of heat stress. Before the plant is removed from its container, it must be thoroughly soaked so the entire root ball is saturated, ensuring it enters the soil with maximum available moisture.
The timing of the transplant is crucial for minimizing heat exposure; only plant during the cooler parts of the day, such as early morning or late evening. When preparing the hole, make it two to three times wider than the root ball but no deeper, which encourages the roots to spread horizontally. Incorporating organic matter, such as compost, into the backfill soil helps improve water retention. Once the plant is placed, the backfill should be gently firmed around the root ball to eliminate air pockets, which can dry out new roots.
Critical Post-Planting Care for Survival
Immediate Watering and Mulching
The first action after planting is an immediate and deep watering to settle the soil and saturate the entire root zone. This deep soak pushes out any remaining air pockets and establishes initial moisture. For the first two weeks, a specialized summer watering schedule is needed, often requiring deep watering daily or every other day during extreme heat. Watering should be slow and deep, encouraging roots to grow downward toward cooler, more stable moisture.
Immediately after the first watering, apply a two to three-inch layer of organic mulch around the plant, keeping it a few inches away from the stem. Mulch acts as an insulator, reducing soil temperature and slowing the rate of water evaporation.
Providing Temporary Shade
For sensitive varieties or during severe heat waves, temporary shading can significantly reduce heat and light stress. This is accomplished with a piece of shade cloth or a makeshift screen positioned to block the harshest afternoon sun. The temporary shade must be set up so it does not rest directly on the plant foliage, which would trap heat and restrict necessary airflow.