At NCOS, one of the main challenges with the timing of the COVID-19 pandemic is that this is the time of year when non-native weeds are growing fast and flowering, and CCBER staff and students are focused on keeping them at bay. The goal is to remove invasive plants before they drop seeds in order to reduce their spread and to give native plants an advantage over resources. Due to the current shelter at home orders, our team of students is not available and only a very minimal crew of staff are able to be on site, which makes it challenging to keep up with all the weeding. So, next time you're out on the Marsh trail and if you feel inspired to pull a weed or two, here is a short guide to differentiating four key weeds from their similar looking native counterparts:
One of the common invasive plants found at NCOS is Sow thistle (Sonchus sp.), a small dandelion-like flowering plant that could easily be confused with two of our native species, Cliff aster (Malacothrix saxatilis) and Silverpuffs (Stebbinsoseris heterocarpa).
Native Native Non-native 
Cliff aster (Malacothrix saxatilis) Silverpuffs (Stebbinsoseris heterocarpa) Sonchus (Sonchus sp.)
Although Cobweb thistle (Cirsium occidentale) and Italian thistle (Carduus pycnocephalus) may appear similar, Cobweb thistle is endemic to California while Italian thistle is native to Northern Africa, Asia, and Western and Southern Europe.
Native Non-native 
Cobweb thistle (Cirsium occidentale) Italian thistle (Carduus pycnocephalus)
Not all mustards are invasive! The diminutive Western tansy mustard (Descurainia pinnata) is native to North America and can be found along the edges of the Marsh Trail at NCOS. It has deeply lobed fern-like leaves and is much smaller than the invasive Wild mustard (Hirschfeldia incana).
Native Non-native 
Western tansy mustard (Descurainia pinnata) Wild mustard (Hirschfeldia incana)
Purple needlegrass (Stipa pulchra) and Ripgut brome (Bromus diandrus) can appear similar from afar, but differences become apparent as you take a closer look. An easy test to tell these two apart is running your fingers from the tip of the seed head towards the stem along the length of the seedhead, but be careful! Ripgut brome has tiny barb-like hairs that will catch on your fingers while Purple needlegrass will feel smooth.
Native Non-native 
Purple needlegrass (Stipa pulchra) Ripgut brome (Bromus diandrus)