What plants harm pea growth?
Written by
Julia Anderson
Reviewed by
Prof. Samuel Fitzgerald, Ph.D.Allelopathic plants -- such as garlic -- exude chemicals that limit the growth of pea roots. I recently learned this, to my dismay, when my pea patch produced 50% fewer pods than my other peas. Marigolds are a common companion plant, but they aggressively compete with peas for phosphorus, especially in acidic (pH < 6.0) soils.
Allium Family
- Onions/garlic: Emit root inhibitors reducing nitrogen uptake
- Leeks: Attract onion maggots that spread to pea roots
- Control: Separate by 36 inches (90 cm) or use raised bed dividers
Flower Bulbs
- Gladiolus: Host thrips pests that destroy pea blossoms
- Dahlias: Require heavy fertilization starving nearby peas
- Alternative: Plant zinnias 24 inches (60 cm) away for pest-eating beneficials
Root Vegetables
- Potatoes: Spread blight to pea foliage in humid climates
- Radishes: Only harmful when planted densely (under 6 inches/15 cm spacing)
- Solution: Interplant with spinach for soil temperature regulation
Prevent soil pest activities through soil testing and planning soil layouts. I like a three-year rotating of peas with a nonlegume crop like corn, which helps break up pest cycles. Implementing raised beds with a fresh soil mix will also further reduce the presence of allelopathic soil chemicals and compounds from your previous crop. I recommend testing your soil pH for the next two to three months, observing both soil moisture and climate. Peas pressure grows best at a 6.5-7.0 neutral pH level.
Planting beneficial companions can include aromatic herbs and some flowers. Mint repels flea beetles, as long as the mint is planted 18 inches or more from the pea rows. Nasturtiums attract aphids away from the pods - I interplant them as sacrificial crops along with marigolds as trap plants.
Water management reduces competition for nutrients. Peas require 1 inch (2.5 cm) of water a week until they flower. Avoid using overhead irrigation near alliums because they have shallow roots that utilize the moisture. Drip irrigation systems keep the foliage dry, preventing blight spread from your nightshade-family plants.
Read the full article: How to Grow Peas: The Complete Guide
