Peas are a popular cool-season vegetable, known for their sweet, tender pods. These plants thrive in temperate conditions, making them a staple of spring and early summer gardens in many regions. Understanding their heat tolerance is key to a successful harvest.
Ideal Temperatures and Heat Thresholds
Pea plants grow best when daytime temperatures are between 55°F and 65°F, with nighttime temperatures no lower than 50°F. Young plants tolerate light frost and grow above 40°F. Temperatures consistently above 70°F cause stress, with significant problems above 75°F. When daily maximums exceed 80°F, pea yields decrease. Prolonged exposure above 85°F can stop growth and cease flower or pod production.
How High Temperatures Harm Pea Plants
Excessive heat impacts pea plants, especially during flowering and pod development. High temperatures, particularly between 87°F and 91°F (30.5-33°C), can drastically reduce seed yield and germination. Heat stress accelerates crop maturity, resulting in smaller plants and reduced biomass. This leads to fewer pods per plant, a lower pod set ratio, and fewer seeds per pod.
Heat also affects pea quality, often leading to small, tough, and less sweet peas. Pollination is vulnerable; high temperatures reduce pollen viability and can cause flowers to abort or drop before setting pods. Additionally, heat stress can make pea plants more susceptible to diseases like dry root rot, particularly with soil moisture deficits.
Identifying Heat Stress
Recognizing the signs of heat stress in pea plants helps gardeners intervene early. Wilting is a common indicator, even with adequate soil moisture, as plants struggle to transpire efficiently. Leaves may yellow, particularly older foliage, and appear scorched or sunburned.
Heat stress also manifests as stunted growth. There might be a premature cessation of flowering or a reduction in new blooms. Poor pod development, including fewer or smaller pods, is another sign.
Protecting Peas from Warm Weather
Protective measures can extend the pea harvest as temperatures rise. Providing shade is effective; shade cloth, typically with 40-70% UV blockage, can reduce ambient temperatures by 10-15°F and cool the soil. Draping shade cloth over hoops or trellises creates a filtered-light environment that reduces heat exposure. For container peas, moving them to a naturally shaded area during the hottest part of the day offers relief.
Consistent, adequate watering is important. Deep watering in the early morning helps plants endure afternoon heat by ensuring the root zone is moist. Mulching around the base of plants with organic materials like straw, leaves, or grass clippings helps retain soil moisture and keeps the soil cooler. This also suppresses weeds, reducing competition for water and nutrients. Choosing heat-tolerant pea varieties, such as ‘Wando’, can improve success in warmer climates or for later plantings.