There are many forages that guinea pigs can eat. Please make sure before feeding to wash thoroughly. Also all forages must come from chemical and pesticide free areas and avoid areas close to roadsides as fumes from cars can contaminate.
Grass can be fed daily in unlimited amounts once your cavies are used to it, otherwise start with a small amount and increase daily for several days.
Dandelion leaves are quite high in calcium, best fed every 3 days or so.
Everything else, use your best judgement and give in small amounts.
Also want to mention, if it's not on this list it may not be edible. So please ask before feeding.
- Grass (common grasses are edible, avoid ornamental grasses), cat grass/wheat grass is also popular and can be grown in pots or containers.
- Clover (Trifollium repens or Trifolium pratense)
- Dandelion (Teraxacum officinale) - pick leaves, stems, flowers (even root OK)
- Anise (Pimpinella anisum)
- Blackberry leaves (Rubus plicatus) - pick young & tender leaves and shoots
- Calendula (Calendula officinalis) - leaves and flowers
- Caraway (Carum carvi)
- Chamomile (Anthemis nobilis)
- Chickweed (Stellaria media)
- Cleavers / Stickyweed / Goosegrass / Bedstraw (Galium aparine)
- Coriander (Coriandrum sativum)
- Cowberry (Vaccinium vitis-idaeae) - berries, leaves in moderation
- Cow Parsley (Anthiscus sylvestris)
- Dog Rose (Rosa canina) - ripe fruits
- Duckweed (Lemna minor) - aquatic
- Fennel (Foeniculum capillaceum)
- Field Violet / Wild Pansy (Viola tricolor)
- Groundsel (Senecio vulgaris)
- Lemon Mint / Melissa (Melissa officinalis)
- Linden / Lime Tree (Tilia cordata or Tilia platyphyllos) - flowers with
pale yellow leaflets - Miner's Lettuce (Claytonia perfoliata)
- Peppermint (Mentha piperita)
- Plantain (Plantago major or Plantago lanceolata)
- Raspberry leaves (Rubus idaeus) - pick young & tender leaves and shoots
- Spearmint (mintha spicata)
- Stinging Nettle (Urtica dioica)
- Shepherd's Purse (Capsella bursa-pastoris)
- Silverweed (Potentilla anserina)
- Vetch (Vicia x)
- Yarrow (Achllea millefolium)
- Whortleberry / Heidelberry (Vaccinium myrtillus) - berries, leaves in
moderation - Wild Chamomile (Matricaria chammomilla)
- Wild Strawberry (Fragaria vesca) - berries and leaves
Another source for forages is
Guinea Lynx :: Common Forages.