| Common Name | Latin Name |
|---|---|
| Rabbitfoot Clover | Trifolium arvense |
| Rattlebox | see Showy Crotalaria |
| Rattlesnake Weed | see Florida Betony |
| Red Clover | Trifolium pratense |
| Red Deadnettle | see Purple Deadnettle |
| Red Morningglory | Ipomoea coccinea |
| Red Puccoon | see Bloodroot |
| Red Sorrel | Rumex acetosella |
| Redroot Pigweed | Amaranthus retroflexus |
| Redstem Filaree | Erodium cicutarium |
| Redtop | see Creeping Bentgrass |
| Redvine | Brunnichia ovata |
| Reed Canarygrass | Phalaris arundinacea |
| Rice Flatsedge | Cyperus iria |
| Richweed | see White Snakeroot |
| Roadside thistle | see Tall Thistle |
| Rosinweed | see Compass Plant |
| Rough Cinquefoil | Potentilla norvegica |
| Roughstalk Bluegrass | Poa trivialis |
| Roundleaf Greenbrier | Smilax rotundifolia |
| Russian Olive | Elaeagnus angustifolia |
| Russian Thistle | Salsola kali |
