Madeira-vine 
Maiden Pink 
Malabar spinach 
Mammillaria bachmannii 
Mammillaria bombycina 
Mammillaria canelensis 
Mammillaria compressa 
Mammillaria elongata 
Mammillaria geminispina 
Mammillaria magnimamma 
Mammillaria parkinsonii 
Mammillaria standleyi 
Marumleaf buckwheat 
Marvel of Peru 
Mediterranean Catchfly 
Mediterranean Saltwort 
Melocactus conoideus 
Melocactus peruvianus 
Menzies' campion 
Mexican Giant Cactus 
Mexican organ pipe 
Mile-a-Minute 
Miner's Lettuce 
Minuartia formosa