Weeds (Pr-Sc)
Prickly lettuce – Scotch broom
- Weeds: Prickly lettuce (China lettuce) – Lactuca serriola
- Weeds: Prostrate knotweed – Polygonum aviculare
- Weeds: Puncturevine (Tackweed, Goathead) – Tribulus terrestris
- Weeds: Purple deadnettle (Red deadnettle) – Lamium purpureum
- Weeds: Purple loosestrife (Purple lythrum) – Lythrum salicaria
- Weeds: Purslane, common – Portulaca oleracea
- Weeds: Quackgrass – Elymus repens (Elytrigia repens, Agropyron repens)
- Weeds: Red sorrel (Sheep sorrel) – Rumex acetosella
- Weeds: Redroot pigweed (Rough pigweed) – Amaranthus retroflexus
- Weeds: Redstem filaree (Stork’s bill, Crane’s bill) – Erodium cicutarium
- Weeds: Reed canarygrass – Phalaris arundinacea
- Weeds: Russian thistle (Tumbleweed) – Salsola tragus (S. iberica, S. kali)
- Weeds: Ryegrass, annual (Italian ryegrass) – Lolium perenne ssp. multiflorum
- Weeds: Salsify (Goatsbeard) – Tragopogon spp.
- Weeds: Scotch broom – Cytisus scoparius