Modifiers matching clover:

• annual,
• wild,
• perennial,

Simple categories matching perennial:

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