2024 Invasive Watch List Species

The plants below are NOT yet reported from Orange County, but are in adjacent areas. We believe these are likely to appear in the county soon.  Please learn a few of these and look for them. If you believe you see any of these, post your observation to Calflora and/or iNaturalist and report them to invasives@occnps. Instructions for reporting are here.

 

Aquatic plants are not included in the OC CNPS Emergent List, due to their difficulty of early detection and often challenging identification. However, several are listed here for reference. See additional information at the bottom of this page.

 


 

Invasive Watch List 2024

 

Ammophila arenaria – European Beachgrass

Calflora information                 
Cal-IPC Information                 

 

Arctotheca calendula – Cape Weed

Calflora information                 
Cal-IPC Information                 

 

Brassica juncea – India Mustard

Calflora information                 

 

Carduus tenuiflorus – Slender Flowered Thistle

 

Carrichtera annua – Ward’s Weed

 

Centaurea calcitrapa – Purple Star Thistle

Calflora information                 
Cal-IPC Information                 

 

Centaurea iberica – Iberian Knapweed

Calflora information                 

 

Centaurea stoebe – Spotted Knapweed

Cal-IPC Information                 

 

Chloris truncata – Truncate Finger Grass

 

Chondrilla juncea – Skeleton Weed

 

Cirsium arvense – Canada Thistle

 

Cortaderia jubata                         

 

Cytisus scoparius – Scotch Broom          

 

Dipsacus fullonum – Teasel

 

Dipsacus sativus – Indian Teasel

 

Elaeagnus angustifolius – Russian Olive

 

Elymus caput-medusae – Medusahead

 

Enchylaena tomentosa – Ruby Saltbush

 

Euphorbia virgata – Leafy Spurge

 

Helichrysum petiolare – Licorice Plant             

 

Heliotropium supinum – Drawf Heliotrope

 

Kochia scoparia – Summer Cypress

 

Lepidium appelianum – Hairy Whitetop

 

Lythrum salicaria – Purple Loosestrife

 

Myoporum acuminatum – Strichnine Bush

 

Pentameris aroides – Annual Pentameris

 

Perilla frutescens – Shiso

Wikipedia information               

 

Phragmites australis – Common Reed

 

Sisymbrium erysimoides

 

Ulex europaeus – Gorse

 

 

Aquatic Plant Note

True aquatic plants are not included in the OC CNPS Watch List or Emergent List, due to their difficulty of early detection and often challenging identification. Nonetheless, species of concern in or near Orange County include:

 

  • Alternanthera philoxeroides – Alligatorweed
  • Hydrilla verticillata – Hydrill
  • Iris pseudacorus – Yellow flag iris
  • Ludwigia hexapetala – Creeping water primrose
  • Myriophyllum aquaticum – Millfoil
  • Myriophyllum spicatum – Millfoil 
  • Pistia stratioites – Water lettuce
  • Potamogeton crispus – Crispate leaved pondweed
  • Salvinia minima – Water spangles
  • Salvinia molesta – Kariba weed