Attracting Beneficial Insects

• Evening primrose attracts ladybugs, pirate bugs, parasitic wasps, crab spiders, damsel bugs, and plant bugs. These bugs prey on beetles, aphids, leafhoppers, mites, flies, caterpillars and many other insects that might prey on nearby plants. Because evening primrose nurtures many beneficial insects, it is considered an insectary companion plant.
  
  

Trapping Problem Insects

• The idea behind trap plants is that plants used for crops planted in large numbers attract many problem insects to feed on them. Trap plants are more attractive to the pests than your crop plants once the insects reach the garden, and distract them from the crops. According to Michigan State University, evening primrose is attractive to "large numbers of lygus bugs, leafhoppers, and Japanese beetles" and "small numbers of thrips, aphids, leaf beetles and weevils."
  
  

Suppressing Weed Seeds

• Plants that are allelopathic prevent nearby plants from germinating, growing, or reproducing properly. Evening primrose is allelopathic to a variety of weed seeds. Allow evening primrose to shed its leaves and flowers in your garden wherever you don't want weed seeds to grow. Avoid using evening primrose in areas where you want to sow seeds.