A Project to Identify and Describe Weed Species in My Backyard

In the last couple of weeks I’ve undertaken the shelter-in-place compliant project of identifying and documenting all species of “weeds” growing in my Petaluma, CA yard (or at least as many as I could). For this project, I’m defining “weeds” to mean any young plants (annuals or young perennials) that have seeded themselves without any help from us (human residents) and that are either completely wild, or have spread out of the locations where they were originally planted by us. This definition then excludes most of the trees on the property as well as many garden plants.

My goal was to identify and photograph each species, do some cursory research on their history and potential edible and medicinal uses, write a little blurb about them, and finally compile this information into an accessible web page. The result of all this work can be found here:

Petaluma Botany Project (Subject to changes / updates!)

So, what did I find?

What I found was 74 species (and counting) of weeds! There are at least a few species I know of that I have not yet included (in part due to difficulty identying a couple of grasses), and almost certainly some additional species that I overlooked or that have not yet sprouted. Presumably, this could possibly amount to another 10-15 species, making a grand total of around 85-90 species, but that’s just a guess.

Let’s break this down with some numbers. Here is how the species I’ve described so far fall into some categories:

  • Edible: 55
  • Not edible: 18
  • Medicinal: 49
  • Not medicinal: 24
  • Native: 13
  • Non-native: 61
  • Trees: 8
  • Onion family: 3
  • Once planted intentionally (sometime in the last 24 years): 8

First things first, let’s talk about edibility. That’s a lot of edible species! Based on the information I’ve found, about 75% of the weed species in our yard have some history of edibility in some form. This doesn’t mean they are good to eat (although many certainly are), but rather that some or all of the plant can be eaten (sometimes only after preparing/cooking it) in some (possibly small) quantity without posing an immediate threat to one’s health. But many really do have glowing reputations as delicious edibles. Some legitimately enjoyable and more popular edible species include:

  • Acer macrophyllum - Big Leaf Maple
  • Allium neapolitanum - Naples Garlic
  • Allium triquetrum - Angled Onion
  • Allium vineale - Crow Garlic
  • Anthriscus caucalis - Bur Chervil
  • Borago officinalis - Borage
  • Calandrinia menziesii - Red Maids
  • Calendula officinalis - Pot Marigold
  • Cardamine hirsuta - Hairy Bittercress
  • Carduus pycnocephalus - Italian Thistle
  • Claytonia perfoliata - Miner’s Lettuce
  • Galium aparine - Cleavers
  • Helianthus annuus - Sunflower
  • Hypochoeris radicata - Cat’s Ear
  • Lactuca serriola - Prickly Lettuce
  • Lamium purpureum - Purple Deadnettle
  • Lepidium didymum - Lesser Swine Cress
  • Malva parviflora - Cheeseweed Mallow
  • Medicago polymorpha - Burr Clover
  • Melissa officinalis - Lemon Balm
  • Nigella damascena - Love-in-a-mist
  • Oxalis corniculata - Creeping woodsorrel
  • Oxalis pes-caprae - Sourgrass
  • Papaver somniferum - Opium Poppy
  • Plantago lanceolata - English Plantain
  • Prunus ilicifolia - Holly Leaf Cherry
  • Quercus agrifolia - Coast Live Oak
  • Quercus lobata - Valley Oak
  • Romulea rosea - Onion Grass
  • Rubus armeniacus - Himalayan Blackberry
  • Rumex crispus - Curly Dock
  • Sonchus asper - Spiny Sow Thistle
  • Sonchus oleraceus - Common Sow Thistle
  • Stachys byzantina - Lamb’s Ear
  • Stellaria media - Chickweed
  • Taraxacum officinale - Common Dandelion
  • Taraxacum erythrospermum - Red-seeded Dandelion
  • Urtica dioica - Stinging Nettle
  • Vicia sativa - Spring Vetch

Of course, not all of these are going to tickle the standard american palate if consumed boiled and plain. If treated well in the field and kitchen, they can shine on the plate! Also, there are several species for which there is very little infomation (if any) on edibility / toxicity one way or the other. Some of these could possibly be edible, but for now are left out of the discussion.

On the flipside, this leaves 18 species (about 25%) categorized as not edible. This either means that the edibility is unknown/unclear, or that the plant is sufficiently toxic to outweigh any potential positive (sensory or nutritional) benefit conferred from consuming the plant. Plants with clear toxicity to humans (that cannot be easily neutralized by cooking, etc.) include:

  • Conium maculatum - Poison Hemlock
  • Euphorbia peplus - Petty Spurge
  • Hedera canariensis - Algerian Ivy
  • Hedera helix - English Ivy
  • Lysimachia arvensis - Scarlet Pimpernel
  • Ranunculus muricatus - Spiny-fruit Buttercup
  • Senecio vulgaris - Common Groundsel

I’ll skip over the medicinal uses, since these can be more involved (and I’m not an herbalist). There certainly are a number of species with clinically supported medicinal value, however.

Non-native invasive plants? We’ve got plenty. Quite a lot of the species occuring here fall into that category. Fortunately many of those also happen to be tasty edibles, though that’s slightly besides the point. We do have 13 tenacious species of native plants growing here, 4 of which are also large trees on our property, and several of which were intentionally planted at some point in the past. Our native weeds include:

  • Acer macrophyllum - Big Leaf Maple
  • Calandrinia menziesii - Red Maids
  • Claytonia perfoliata - Miner’s Lettuce
  • Epilobium ciliatum - Slender Willow Herb
  • Eschscholzia californica - California Poppy
  • Galium aparine - Cleavers
  • Helianthus annuus - Sunflower
  • Phacelia distans - Common Phacelia
  • Prunus ilicifolia - Holly Leaf Cherry
  • Quercus agrifolia - Coast Live Oak
  • Quercus lobata - Valley Oak
  • Stachys rigida - Rough Hedgenettle
  • Urtica dioica - Stinging Nettle

The species in bold are the only native species that have managed to spread into our yard from outside without ever being intentionally planted at some point. These tough cookies (basically, invasive native plants) have managed to compete with all those other invasive non-natives out there and stay stong – nicely done! With the possible exception of phacelia (a great pollinator species), all of these species have edible and/or medicinal value as well!

What am I allowed to pull?

Ok, so which of these species are we probably better of pulling, or at least keeping in check? From my perspective, those with edible and/or medicnal and/or aesthetic value would be ranked higher than those without, and native plants would be ranked higher than non-natives across the board. The non-native, inedible plants in our yard are the following:

  • Acanthus mollis - Bear’s Breech
  • Conium maculatum - Poison Helmock*
  • Cotoneaster lacteus - Milkflower Cotoneaster
  • Cotoneaster pannosus - Silverleaf Cotoneaster
  • Delairea odorata - Cape Ivy
  • Euphorbia peplus - Petty Spurge
  • Geranium purpureum - Little Robin
  • Hedera canariensis - Algerian Ivy
  • Hedera helix - English Ivy
  • Lysimachia arvensis - Scarlet Pimpernel*
  • Photinia serratifolia - Taiwanese Photinia*
  • Poa annua - Annual Bluegrass
  • Ranunculus muricatus - Spiny-fruit Buttercup*
  • Senecio vulgaris - Common Groundsel
  • Tanacetum parthenium - Feverfew
  • Torilis - Hedge Parsley
  • Trifolium hirtum - Rose Clover

In this list, species colored blue have clear medicinal value (or are at least commonly used as such), those with an asterisk (*) have some limited or historical medicinal value, and those in bold text are relatively abundant in our yard. For the sake of diversity, we can for now set aside the species that are relatively sparsely representated in our yard. And while it is certainly interesting that some plants have medicinal value, I don’t think we need to encourage the proliferation of species for that reason alone (since we will make little use of this fact in reality). There are also some non-native edible species that are extremely abundant in our yard, and it seems sensible to keep their populations in check. Having said that, we can/should probably focus on limiting the spread of the following abundant species:

  • Acanthus mollis - Bear’s Breech
  • Arum italicum - Italian Lords and Ladies
  • Borago officinalis - Borage
  • Bromus diandrus - Ripgut Brome
  • Conium maculatum - Poison Helmock
  • Convolvulus arvensis - Common Bindweed
  • Delairea odorata - Cape Ivy
  • Euphorbia peplus - Petty Spurge
  • Geranium dissectum - Cutleaf Geranium
  • Hedera canariensis - Algerian Ivy
  • Lamium purpureum - Purple Deadnettle
  • Medicago polymorpha - Burr Clover
  • Nigella damascena - Love-in-a-mist
  • Oxalis corniculata - Creeping Woodsorrel
  • Oxalis pes-caprae - Sourgrass
  • Poa annua - Annual Bluegrass
  • Senecio vulgaris - Common Groundsel
  • Torilis - Hedge Parsley

I’ve colored this list sort of arbitrarily by management priority, where species in red are the highest priority for reducing population count and limiting spread, those in megenta are medium priority, and those in blue are the lowest priority. All of the species that do not appear on this list are either native, especially valuable for their edible, medicinal, or aesthetic properties, or exist in low numbers on our property. There aren’t really any species that I think we should eliminate completely, but there are so many additional species which aren’t growing on our property (yet!) that it would be great to make a home for.

This has been a really fun and educational project, and it’s tempting to extend it to other areas that I frequent. One of the upsides of having so many non-native invasive species around is that becoming familiar with them is very applicable to many other disturbed areas around the world. It is awesome to have the luxury of hiking in amazing wilderness areas and seeing countless new plants and flowers (and right now, mid-COVID-19 that really is a luxury that most people don’t have), but it’s also fascinating how much there is to discover and learn in your own back yard! For now, maybe my neighbors will get a break from seeing me crawling around in the dirt when they walk by. But there is still plenty more discovering to be done, both in the wild and in the kitchen!

Christoph