Modifiers matching clover:

• annual,
• wild,
• perennial,

Simple categories matching perennial:

• plant,
• herb,
• allergen,
• clover,
• seed,
• tree,
• planting,
• grass,
• crop,
• group,
• legume,
• vegetable,
• forage,
• pest,
• veggie,
• issue,
• bunchgrass,
• weed,
• pasture,
• host,
• wildflower,
• vine,
• ornamental,
• species,
• antigen,
• flower,
• shrub,
• fruit,
• native,
• river,