Austrian Winter Peas (Pisum sativum) are a popular, cool-season annual legume primarily grown as a cover crop. They improve soil health by fixing atmospheric nitrogen and adding organic matter. Using them in a crop rotation system helps reduce the need for synthetic fertilizers and prevents soil erosion during winter. Understanding the correct planting window is crucial for maximizing these benefits.
Primary Timing Considerations
The optimal time to plant Austrian Winter Peas (AWP) is in the late summer or early fall, which allows the plants to become well-established before the soil freezes. The most important factor is planting approximately four to eight weeks before the average first hard frost date for your specific region. This timing is necessary for the seedlings to develop a strong root system and sufficient top growth to survive winter dormancy.
Planting too late prevents the pea from developing enough biomass to survive the cold, which can lead to winterkill. For example, in a moderate climate, planting in mid-September may be ideal, but in colder northern climates, planting may need to occur as early as mid-August. Regional climate variations, often guided by USDA hardiness zones, heavily influence the exact calendar date.
While fall planting is preferred for maximum nitrogen contribution, AWP can also be sown in the early spring in areas with extremely harsh winters. Spring planting shortens the growth cycle, limiting the biomass and nitrogen produced. However, the peas still offer benefits like soil protection and weed suppression during the spring growing season. The minimum soil temperature for AWP germination is approximately 41°F, which is a useful benchmark for planting decisions.
Preparing the Soil and Seed
The first step before planting Austrian Winter Peas involves specific preparation of the seed to ensure effective nitrogen fixation. As a legume, the pea must establish a symbiotic relationship with specific soil bacteria, which is achieved through seed inoculation. The seed must be coated with the correct strain of Rhizobium leguminosarum (the Pea and Vetch group) to form nodules on the roots where nitrogen is converted into a plant-available form.
Inoculation directly impacts the plant’s primary benefit as a cover crop. Once inoculated, the seed should be planted into a prepared seedbed using drilling or broadcasting. Drilling the seed to a depth of 1 to 1.5 inches is generally the most reliable method for establishment.
AWP performs best in well-drained soils, with loamy or clay loam textures being ideal. The soil pH is also a factor, with the peas preferring a slightly acidic to neutral range, ideally between 6.0 and 7.0.
Managing Growth and Termination
After a successful fall establishment, Austrian Winter Peas will enter a period of dormancy or significantly slowed growth during the coldest winter months. The plants exhibit good cold tolerance, with established stands capable of surviving temperatures as low as 10°F for short durations. Once spring arrives and temperatures rise, the peas will resume vigorous growth, quickly generating substantial biomass.
The management decision after overwintering is determining the proper time for termination. To maximize the nitrogen contribution to the following cash crop, the peas should be terminated when they are in the full-bloom stage, which occurs before they set seed. This timing ensures the greatest accumulation of organic matter and nitrogen in the plant tissue.
Termination can be achieved through mechanical methods, such as mowing or light tillage, or with a herbicide application. If using a roller-crimper, the peas must have reached a sufficient height, often 14 inches or more, to be effectively terminated. Terminating the peas two to three weeks before planting the subsequent crop allows the residue to begin breaking down. Leaving the terminated residue on the soil surface acts as a mulch, helping suppress weeds, conserve soil moisture, and prevent erosion.