Peas (Pisum sativum) are a beloved cool-weather legume often planted directly into the garden soil as soon as the ground can be worked in spring. However, starting seeds indoors provides a head start on the short growing season, which necessitates transplanting the young seedlings. This process of moving the delicate plants from a sheltered, indoor environment to the garden requires careful attention to timing and technique. Successful transplantation relies on understanding the plant’s environmental needs and executing the move with minimal disturbance to the roots.
Environmental Factors Dictating Timing
The timing of transplanting peas is dictated by soil temperature, which is a more accurate indicator than air temperature for root establishment. Pea seeds and seedlings thrive when the soil temperature is consistently between 45°F and 55°F, though they can germinate in soil as cool as 40°F. Checking the temperature several inches deep provides the most reliable data for determining the correct day to plant.
Peas are naturally frost-tolerant and can generally withstand a light spring frost without significant damage. However, the risk of a hard freeze (temperatures consistently in the low teens) should have passed before moving the young plants outdoors. A common guideline is to aim for transplanting around four to six weeks before the last expected frost date in your specific region. This cool period allows the plants to develop before the heat of late spring and summer arrives, as pea plants struggle when temperatures exceed 80°F.
Maintaining soil moisture is also a consideration for timing. Overly wet soil can lead to root problems like rot, especially in cold conditions. Choosing a day when the soil is workable and not saturated helps ensure a healthy start for the transplanted seedlings.
Essential Preparation: Hardening Off
Before any outdoor planting occurs, the seedlings must undergo a transition known as hardening off. This process gradually acclimates the indoor-grown plants to outdoor elements like direct sunlight, wind, and temperature fluctuations. Without this preparation, the soft foliage and tender stems developed under indoor grow lights can be severely damaged or killed by sudden exposure to the sun’s ultraviolet rays and strong breezes.
The hardening off period typically spans seven to ten days and should begin once the seedlings have developed their first true leaves. On the first day, place the pea plants in a sheltered, shady spot outside for only one to two hours, ensuring they are protected from strong winds. Over the following days, the duration of their outdoor exposure should increase by an hour or two daily.
The amount of direct sunlight they receive must also increase gradually during this period. By the end of the transition, the seedlings should be able to tolerate several hours of direct sun and remain outside overnight, provided temperatures stay above freezing.
The Mechanical Process and Immediate Aftercare
Peas possess extremely sensitive roots and do not recover well from disturbance. This makes transplantation challenging. To minimize root shock, start pea seeds in biodegradable pots, such as peat or coir pots, or in specialized root trainers. These containers allow the entire unit to be planted directly into the garden soil, preventing the roots from being handled.
When planting, dig a hole slightly larger than the container or root ball and position the seedling at the same soil level as it was growing indoors. For those not using biodegradable pots, gently push the root mass out from the bottom, handling the root ball as little as possible. Space the transplants approximately two to three inches apart along their support structure, which should be in place before planting to avoid later root damage.
After backfilling the hole with soil, lightly firm the area around the base of the plant to eliminate air pockets, being careful not to compact the soil too tightly. The immediate aftercare involves a thorough but gentle watering to help settle the soil and establish root-to-soil contact. Providing initial support, such as a trellis or stakes, is important for climbing varieties to prevent the delicate vines from sprawling on the ground. If an unexpected cold snap is predicted after planting, a temporary row cover can offer additional protection during the first few nights.