Do weeds rob soil of nutrients?

Wholy Cow, what an awe inspiring discussion this thread has become, glad I've been watching in on the side lines.
Lots of great ideas and answers.
Tim, great subject for this thread, thanks for starting it.
Everyone else, fantastic responses.

weeds are one of my favorite subjects, it is interesting to see what others views of these primary succession plants are and how they incorporate them, or exclude them.

Redhawk

Bryant RedHawk wrote:Wholy Cow, what an awe inspiring discussion this thread has become, glad I've been watching in on the side lines.
Redhawk

I was wondering what was keeping you from the thread, BR. And also, when I exclaim, it's "partially cow" so as to not invoke the whole cow, cuz, you know, that'd be wasteful. Hahahaaaaa

I personally leave all “weeds” that aren’t growing becoming excessive. I chop and drop everything. Sometimes I pull them. There is a loss of microbes, but it also does small scale aeration of the soil, give some take some..  

Welcome to Permies, Jas!  Glad to hear that this is working for you as well.  Where are you posting from and what sort of gardens do you have?

i always pile pulled weeds around my plants as a mulch layer. saves moisture and feeds my plants as it breaks down.

Hi Steve Bossie.  I'm glad that this works for you:

i always pile pulled weeds around my plants  

This would work with some of my weeds, but with many they would simply re-root and take off again (all my grasses, hawkweed, ox eyed daisies, hedge nettle, to name a few); this time they would root directly against my chosen crop plants.

Method A, for readily rooting weed use, make a green weed tea maker, it is almost the same as a compost tea set up, gives back most of the nutrients asap and leaves compostable, non re rooting stems and roots.
Bag the weeds for easy removal, brew for one week (this drowns the roots). The safe side would then lay the brewed weeds on some sort of screen in the sun to dry completely before adding to compost or using as mulch.

Method B, sun dry root systems of readily rooting weeds for one week before using as; a, mulch, b, compost material, c, worm food.

Method C, feed to hogs, they love most any weed and will process them for you.

(just some ideas)

Redhawk

Roberto pokachinni wrote:Hi Steve Bossie.  I'm glad that this works for you:

i always pile pulled weeds around my plants  

This would work with some of my weeds, but with many they would simply re-root and take off again (all my grasses, hawkweed, ox eyed daisies, hedge nettle, to name a few); this time they would root directly against my chosen crop plants.

i don't have that problem because i mulch every spring w/ 3in. of green wood chips around all my plants and trees. the few weeds that come thru get layed on top of the mulch. no N available plus the mulch desiccates them further= dead weeds! ;)

Bryant RedHawk wrote:Method A, for readily rooting weed use, make a green weed tea maker, it is almost the same as a compost tea set up, gives back most of the nutrients asap and leaves compostable, non re rooting stems and roots.
Bag the weeds for easy removal, brew for one week (this drowns the roots). The safe side would then lay the brewed weeds on some sort of screen in the sun to dry completely before adding to compost or using as mulch.

Method B, sun dry root systems of readily rooting weeds for one week before using as; a, mulch, b, compost material, c, worm food.

Method C, feed to hogs, they love most any weed and will process them for you.

(just some ideas)

Redhawk

my chicks ducks and geese love weeds! plus the dandelions, lambs quarters and other dynamic accumulating plants are chock full of nutrients. i have a section of lawn under my pines i intentionally let grow just to feed to my birds. the eggs yolks are a deep orange and taste fantastic! just planted a corner of the yard with more ''weeds''. borage and nettle for us and the birds. ;) funny you mention the tea. I've done it using just meadow grass and truthfully, the tea is as good as the comfrey tea i make. free fertilizer!

Tim Kivi wrote:Some permies say "there's no such thing as a weed". My gardening books all day that weeds rob the soil of nutrients meaning other plants can't access them.

What's the deal?

I've been putting on a mulch of pie seaweed on my garden bed. I top it with large dried whole maple leaves. Weeds and vegetables are all thriving. I have no problem with the weeds, unless my veggies could do better without the competition.

Now and then I simply pull a weed/grass out while picking my veggies, rip off the root from the leaves and drop it back on the ground as a mulch. Am I doing the right thing?

Now that I have a little time, I would like to address Tim's original question(s).

First let us look at the statement "there's no such thing as a weed" while true because all plants have their place in the workings of nature (which is to make soil rich enough to support life forms like microorganisms, worms, plants and all the other forms of life found on terra firma),
This precludes the term weed.  Humans call plants growing where they are not wanted "weeds" even a rose could be considered a weed if it is not in a place we want it to grow.  
All plants take nutrients from the soil, this is how they make their living and what allows them to grow, water is considered a nutrient.
So yes, "weeds" will take nutrients from the soil and since the plant fits the description of a weed when it grows where we want something else to grow, it could be considered a "robber" of nutrients.
Gardening books, for the most part, subscribe to the "modern agriculture" model, promoting localized monocrop growing (flower beds, etc. are usually designed to grow groupings of specific plants).
In gardening, most people forget that growing a single species of say Nasturtium in a garden bed, is indeed mono crop growing, even if it is so localized as to be a 2 foot square piece of a garden bed.

In nature what we call weeds are really primary or secondary succession plants, they have the job of putting roots into the ground, activating bacteria through their exudates which causes release of enzymes that dissolve minerals from rocks (dirt is ground up rocks).
So, when growing where we want them to grow, they are the good guys, if they are growing where we want something else, that isn't able to out compete the "weed" then they are a nuisance plant and are typically removed, taking with them the nutrients they have incorporated into their bodies.
If we just toss them to the garbage, we have lost those nutrients. If we do something else with them ending up back on or in the soil, then we have recovered those nutrients, thus saving the need to make an amendment to put back what we threw away.

Every one who has contributed to this thread already has brought this up in an excellent set of ways to put back the weed goodies. Bravo!

It is always the right thing when you use what you removed (plant material wise specifically) to make something you put back to the soil from which it was removed (recycling or closing the hoop of life), this works regardless of whether we keep some of it for our own food supply or use the whole plant as the new mulch, tea, or compost.  Nature wastes nothing, neither should we. One way or another we should always be trying to close the hoop when it comes to our soil, the more we succeed the better our soil becomes and the more life it will support for us.

Redhawk

Great conversation. I look at weeds as carbon fixators and nutrient accumulators and chelators, as well as soil conditioners. I do not worry about it if a “weed” is not shading out my wanted plants, it’s better than bare soil and trades sugars and nutrients via soil life that become more available to all plants around it.  Ultimately, Whichever plant has the greater photosynthetic surface area will ultimately win any transpiration powered tug of war for water and nutrients that may occur in times of scarcity. Unless you have more than enough organic matter in your soil, I’d let your weeds put it in there for you and chop n drop/feed to animals unless you have a choice plant to put there instead.

I have lots of docile ants who eat flowers. We also have horned lizards who survive on a diet of these ants.

Even if the weeds were not good for my soil, getting rid of them would cause much damage to the wildlife and my trees/plants.

I like the way they look too. 🙂

Ben Zumeta wrote:Great conversation. I look at weeds as carbon fixators and nutrient accumulators and chelators, as well as soil conditioners. I do not worry about it if a “weed” is not shading out my wanted plants, it’s better than bare soil and trades sugars and nutrients via soil life that become more available to all plants around it.  Ultimately, Whichever plant has the greater photosynthetic surface area will ultimately win any transpiration powered tug of war for water and nutrients that may occur in times of scarcity. Unless you have more than enough organic matter in your soil, I’d let your weeds put it in there for you and chop n drop/feed to animals unless you have a choice plant to put there instead.

i agree. bare soil is dead soil. when im not growing a crop, i either seed a cover crop or let the weeds do it for me. the reson they show up in the 1st place. mother earth doesnt like to be naked and exposed. ;)

I've been keeping a record as I find info of what nutrients different "weeds" accumulate.  All the legumes, clovers, vetches, bird's foot trefoil, black medic, etc. fix nitrogen from the air and add it to the soil directly or indirectly.  Yellow sweet clover accumulates phosphorus.  Creeping buttercups accumulate potassium.  Chickweed accumulates phosphorus and potassium.  Lambs quarters accumulates nitrogen, phosphorus, and potassium(doesn't get much better than that), calcium and manganese while loosening the soil.  Broadleaf Plantain accumulates calcium, sulphur,magnesium, manganese, iron and silicon.  Dandelion accumulates phosphorus, potassium, calcium, copper, iron, magnesium, and silicon while loosening the soil.  'Nuff said?

Ray

After reading something in the Mother Earth News, I set out to make a non-aerated tea from a few plants (comfrey, clover, lupine, and rose mallow), shaking the container a few times a day (I suppose it is aerated, after a fashion).  Sometimes a bit of composted chicken or goat poop, if handy, and some coffee grounds.  The recipe I read was for shredded comfrey leaves, grass clippings, dried chicken poop, and a bit of urine.

After the third day, it has a strong scent but it's earthy, not putrid.  I started using it as a tonic on plants that weren't doing as well as I wanted.  (I'm not sure if I want to get involved with getting the equipment to make compost tea.  I need to learn more.)

Then I began reading this thread.  It's got me thinking about understanding the soil food web, and returning the best, the essence, of the "weeds" to the soil.  My compost-making (like my "tea" brewing) is also fairly haphazard, and the chickens do most of the work.  I'm eager to improve my soil, and to find the balance between biodiversity and choked-out, shaded, or overrun vegetables!

So much to think about in this thread.

You won't get nitrogen back by harvesting weeds.

My method it collect grass cuttings in yard, go around with bucket and pick axe dandelions in yard, other weeds.

then drop them into my solar cooker trash cans.   Later put results on garden beds.

Plants gather most of tbe nitrogen they use from the air, soil nitrogen is used more by the micro organisms and the plant root tips. This means that most amendment nitrogen is not benefiting plants directly but indirectly through the organisms in the microbiome.

Redhawk

Bryant RedHawk wrote:Plants gather most of the nitrogen they use from the air, soil nitrogen is used more by the micro organisms and the plant root tips. This means that most amendment nitrogen is not benefiting plants directly but indirectly through the organisms in the microbiome.

Redhawk

Interesting point, we are usually taught about carbon dioxide + oxygen.  Like you point out there are many NPK, and other organic and inorganic things that play a in action for a garden.

Michael Moreken wrote:You won't get nitrogen back by harvesting weeds.

Three ways you get nitrogen back when harvesting weeds.

1.  You put that weed through an animal.  The cow, sheep or chicken harvests the weed and within a day, deposits it back out onto the ground in a N-rich form that is highly beneficial to the ecosystem.

2.  You compost that weed with a carbon source that captures the N rather than lets it gas off.  A properly constructed compost pile captures up to 80% of the N from the weeds/ingredients in the pile.

3.  A N-fixing weed has nitrogen nodules on its roots.  When harvested, that N is left below ground as the weed is chopped off at the soil surface.  If you don't harvest the weed, the plant will use it up by making seed, leaving little of it in the ground.

I grow a lot in large containers.
Often my containers started growing "weeds" before I'm ready to plant in them.
Sometimes its smartweed, sometimes lambs quarters, sometimes entire trees.
Once things get big enough to sort of identify , I "weed out" the less desirables and feedthrow  them to the chickens.
I don't know what part of it they eat, but they make it disappear really fast.

As a result, I have two barrels that are overflowing with cilantro , tomatoes, onions and a grape vine.
I only planted the grape vine and the onions, and I recently "weeded"  (pruned) the grape vine to keep it from competing for sun with the tomatoes!


The barrels that failed to sprout "weeds" have tomatoes starts planted in them.
They are puny compared to the tomato "weeds"
They had had a mulch of rabbit bedding applied last fall, and I transplanted a lot of tree seedlings out of them.
Now I'm thinking I should sow some "weed" seeds in with the puny tomatoes starts.


All told, the "weeding" I do is pretty beneficial for me.
Every weed suppresses some other weed, and seems to do the soil some good.
I get to interact with my gardens, and at a minimum I get a harvest of compostables.

Dynamic Accumulator Plants - plants that accumulate ten times more than usual of at least one nutrient.
 I'm not sure why the nitrogen isn't listed for any of the plants except the highest.....I assume all plants have quite a bit of nitrogen......

Ray, if there's a number in the chart is it 10x or is it only if it's highlighted that it's 10x normal?

Mike, the highlighted amounts are the highest for any plant tested of each nutrient or mineral.  By the way, you can click on the table to enlarge it.  Not all plants have been analyzed,  and I'm presuming the author couldn't find nitrogen values to add for all the listed plants.  As you may have noticed, lots of information is available for vegetables and even more for industrial crops.  But weeds have not received as much attention, and information is harder to find.  One has to "read between the lines"!  For example, I wanted information on the value of buttercups.  One site declared that in addition to being an undesirable weed because of toxicity to cattle, they rob the soil of potassium!  O.K.  Well the only way they rob a lawn of potassium is if you gather them up and send them off to the garbage collectors.  If you mow and mulch or compost them, why then they are potassium "accumulators" !

There was more information with the chart I posted and I'm going to try and retrieve and post it.  But I had a difficult enough time just being able to copy and post the chart, so we'll see if I can....

Ray

How does the nutrient content of comfrey compare to an average plant? A common claim is that comfrey contains high levels of nitrogen, phosphorus and potassium.
Two sources which analyzed comfrey came up with similar values of NPK which for simplicity can be rounded off to 3-1-5.
What is the NPK of some common plants?  That is not easy to find, but here are some found by Robert Pavlis:
• Alfalfa 2.5-1-2
• Clover, crimson 2-0.5-2
• Corn gluten meal 9-1-0
• Cotton seed meal 6-0.4-1.5
• Rye, annual 1-0-1
• Seaweed 1-0.5-1
• Soybean meal 7-2-1
Are these average plants? None of the above plants are dynamic accumulators by the definition used by Robert Pavlis, so they are not considered to have high NPK values. It seems reasonable to consider them to be average plants. When you compare comfrey at 3-1-5, it is not much better than the average list – it is certainly not ten times better.


If you download the chart here:   https://mega.nz/file/U8YySKjC#sh8Kr3H-IkPDAKFXIT1qD2uIh_zTYBT0K8_ybgQ6nNo

you can get a lot more information, especially long lists of many plants with their amounts of just Nitrogen, just Phosphorus, just Potassium, etc. etc. for the whole list of minerals.  Most of them are vegetables, fruits, or edibles, since that's what has been tested....

Joseph Lofthouse wrote:In one of my fields, purslane is a tremendous problem. In every other field, if I see a purslane plant, I pull it up, and hike to the nearest paved roadway, and deposit the plant onto the hot asphalt: To be scorched, and squished. I don't care about the lost nutrients. Seems like a good trade-off.

Too sad Joseph. Purslane is very nutritious. It can be dried and used in powdered form many ways. It will not grow back as readily once pulled - in my experience at least - but I don't know why. I've tried spreading the seeds but they didn't grow either. I've read it's a bi-annual plant. It is frost sensitive. Maybe nature is offering you the opportunity to harvest it and use it or to share it with those who might gain health benefit from it.  I'm thinking of  our fine brother Paul W. here...
https://www.webmd.com/diet/health-benefits-purslane
https://www.earth.com/earthpedia-articles/10-surprising-purslane-benefits/
https://www.healthline.com/nutrition/purslane

Recent soil science webinars have emphasized that plants exudate sugars back into the ground to feed beneficial soil organisms.   Weeds are often the plants that are best adapted to the current state of the soil therefore the best at feeding the soil at that time.  The general consensus of this thread from experienced users seems to be: remove the weeds when they are detracting from your objective and feed them back to the soil from the surface.   Weed covered soil is healthier than  bare exposed soil being reduced to dirt.  

Denise Cares wrote:

Joseph Lofthouse wrote:In one of my fields, purslane is a tremendous problem. In every other field, if I see a purslane plant, I pull it up, and hike to the nearest paved roadway, and deposit the plant onto the hot asphalt: To be scorched, and squished. I don't care about the lost nutrients. Seems like a good trade-off.

Too sad Joseph. Purslane is very nutritious. It can be dried and used in powdered form many ways. It will not grow back as readily once pulled - in my experience at least - but I don't know why. I've tried spreading the seeds but they didn't grow either. I've read it's a bi-annual plant. It is frost sensitive. Maybe nature is offering you the opportunity to harvest it and use it or to share it with those who might gain health benefit from it.  I'm thinking of  our fine brother Paul W. here...
https://www.webmd.com/diet/health-benefits-purslane
https://www.earth.com/earthpedia-articles/10-surprising-purslane-benefits/
https://www.healthline.com/nutrition/purslane

I second Denise's motion.  If I found my field overwhelmed with purslane, I might start by pulling the purslane as Joseph does. But noting that this field is a evidently an excellent location for purslane, I would then go back and replace the "weeds" I had pulled with a cultivated variety of purslane - there are several - and let it grow along with whatever other crop I had originally desired there.  Then I would harvest and eat the purslane!  I love the stuff and frequently plant it in my own garden (where, unfortunately, it is usually destroyed by deer, who love it even more than I do).  I make a couple types of fresh salad with it.  Very tasty.  I understand that it shows up cooked in some Mexican dishes, but I've not yet tried cooking it.

BTW, people write that purslane will aggressively self-seed.  Unfortunately, I've not experienced that with my cultivated varieties.  And the one time I tried direct seeding it, I got zero germination.  I usually make seed starts in potting mix - good germination in that setting - or else I buy transplants.  If you can't find purslane to transplant in a nursery's vegetable area, sometimes you can find it in the ornamental area.

A part of this thread has diverged from the original question - are weeds good or bad? - to address instead what is the best way to recycle weeds once you have pulled them or cut off their tops: Chop & Drop vs Compost.

Several have argued that a compost pile is a more efficient way to recycle your vegetative nutrients, since mulching with your weeds - i.e. chop & drop - allows much more of the nutrients to off gas than occurs inside a compost pile, particularly nitrogen.  My understanding is that this is accurate.

However, I don't necessarily conclude that composting is therefore the preferred method.  I would say, it depends on your circumstances and preferences.  Composting is more efficient in terms of nutrients, but chop & drop is more efficient in terms of time and effort.

I would also point out that there is a middle path.  Ruth Stout-style gardening seems to me to combine the attributes of both composting and chop & drop.

So, I would tentatively propose that this is then actually the optimal process.  And sometimes, I do so.  But most of the time I am lazy and hurried, so I revert to chop & drop.

To address the OP's original question - are weeds good or bad; to pull or not to pull? - I have an alternate point of view that I don't believe anyone has expressed yet.  I propose that the OP's dilemma actually begs a different question: is your garden designed according to good permaculture principals if you have so many weeds in the first place?

To be sure, a few weeds here and there are inevitable, regardless of your design.  Who cares?  Pull them, or not, as you like.  But if you have weeds that are engulfing, overtopping, overcrowding, or otherwise posing an existential threat to your crop, seems to me that something is fundamentally wrong.  Perhaps your crop is just weak?  If so, why?  Maybe your transplants or seedlings got off to a rough start?  Could you be planting the wrong things in the wrong place?  Does your garden have good soil and appropriate light exposure?

Any of these questions could reveal circumstances that might favor weeds over your crop.  But the weeds in this scenario are the symptom.  I am suggesting that we address the underlying problem rather than worry overly much about the symptom.

First off, some disclaimers...  I totally acknowledge that, as with everything, it all depends because there are many styles of gardening we could be talking about and many different objectives the gardener could be aiming for.  We could be talking about a patio garden, a kitchen garden, a food forest, or a field of row crops.  One garden might be optimized for minimal time commitment, another optimized for minimal inputs, yet another optimized for profit.  Then again, one might argue that good permaculture principals can be applied to all cases, just in different ways to different degrees.  For now, let's not wade into that argument.

Further, I of course admit that the best design can be hindered, if not outright undone, by poor implementation.  In fact, I more than acknowledge this; I personify it.  I fancy myself a half-way talented permaculture designer, and I am in fact PDC certified.  Yet some of my results in practice have been pathetic, usually because I make dumb mistakes, often born out of a lack of time and labor to dedicate to my projects.  Transplanting trees that die or languish because I failed to water them sufficiently during establishment; letting valued plantings languish and die because everything else grows too tall and thick and I'm years overdue in chopping it back; etc.  I have 20'-tall weed trees in my food forest.  Need I say more?

Sometimes, I have also seen poor results for reasons that I cannot easily explain.  Fruit trees that grow strong and healthy, yet have not born a crop after 10 years.  Why not?  Whatever, I soldier on, keep trying, keep replanting.

But having given my disclaimers, here is my point: a good permaculture design should account for weeds in the first place, and not just through endless hours of weeding or hoeing.  This could be in one of four ways (probably more, but four that I can think of right now).  Or, perhaps in several of these four ways at once.

1) This is the simplest, which I can express in one word: mulch!  As some have pointed out above, weeds are born of bare soil.  That is where the seed bank lies.  Nature abhors bare soil.  We permies emulate nature.  So, let your mulch be thick and rich!  This will not eliminate weeds, but it should give you a good head start against them.  This will be more difficult if you are direct-seeding annuals, but it can still be done with a little patience and care.

2) Not all mulches are brown.  Design your polyculture with multiple layers.  One of these should be a groundcover, which some also call a living mulch.  This makes just as much sense in your kitchen garden as in your food forest: let those squash and sweet potato vines loose underneath your okra and tomatoes!  Take the space your weeds would otherwise occupy and fill that space with an appropriate and desired planting.  Several posters above argued that weeds are good because they add diversity and biomass to your soil food web.  Excellent and very true.  I currently let weeds occupy several of the layers in my food forest.  But if you can do the same thing with a variety of different crop species at different levels, then you can enjoy the same results without using the dreaded word "weed."

If your garden design involves large scale row crops and a tractor, will you be able to implement this same technique, or will you crush your groundcover crops under your tires?  Perhaps you can, with a little creativity and likely a little compromise.  But it won't be nearly as easy as if you were gardening on foot.  I face this same difficulty even in a small scale kitchen garden.  Gardening from a wheelchair, I am become the vehicle.  It makes many common permaculture techniques difficult.

3) Fight weeds with weeds.  I love my spinach and lettuce and tomatoes and such, but studying permaculture has also opened my eyes to the value of atypical crops.  Select among your crop species ones that are vigorous and thick growing and self-seeding - i.e. ones that "grow like a weed"; some above have mentioned lambs quarters - and use your "weed crop" to suppress other weeds.

At least in parts of the garden.  Got to have at least a few tomatoes!

4) Okay, this one's a little bit of a cheat, but...  Make peace with your spontaneous weeds by mentally redefining them as another form of crop.  Now we are circling back to the ideas that others above have already discussed, which don't reduce weeding so much as put the weeds you remove to productive use.  This could be more laborious, depending on your setup and your preferred approach.  If you count on repurposing your volunteer biomass to productive use in your garden design from the get go, then it is a now harvest.  And if you're harvesting it, is it really still a "weed"?  You could do this by composting your weeds, making weed tea for fertilizer, or feeding your animals with them.  If you can find a way to let your animals graze your weeds in place without excessive damage to your main crops, then it is really a win-win!

I've involved myself with many threads on Permies, and this is one of my favorites.  There are so many thoughtful and insightful posts here about a topic that I love that it just makes me smile so much to revisit it.  Some really good points made recently by Mathew Nistico and others highlight the potential of this thread's topic for further exploration.  Kudos all.  Great work.      

It stands to reason that if you have a weed growing close to a cherished plant, the weed is *also* pulling nutrients away. However, once the weed is removed and used as tea, it is a great addition, putting nutrients *back* in the soil for your cherished plants' joy.
On the plus side, a growing weed is also shading the soil right next to your cherished plant, so that's a benefit too: it helps cool the soil and keeps moisture near.

I try not to refer to them as weeds now, but more weedy species.
When you think of weeds, it is worth looking at what the weed does. Cape weed for instance grows very well in areas that are low in calcium. Their deep tap root helps to bring calcium up to the surface which makes it available for other plants after it dies and breaks down.
I think understanding your weeds and perhaps look at them more as moving nutrients rather than "a weed" is beneficial.  Elements don't break down, but shift and move around.
If you feel they are robbing your soil of nutrients, then pull them as soon as possible.  If they are taking over, you need to get onto them before they seed. Just remember what you are pulling up has your nutrients, so you don't want to throw it away.
I hope this helps.

Cécile Stelzer Johnson wrote:It stands to reason that if you have a weed growing close to a cherished plant, the weed is *also* pulling nutrients away.

Even this, though...if my cherished plant has shallow roots and the weed has a deep tap-root, is it pulling nutrients away? Even if they have similar root-needs, won't the plant on the left tend to grow roots out to the left while the plant on the right will grow more roots to the right, so together they'll cover more ground, mining a more diverse array of nutrients, and then trading what they find with each other?

And, I mean, I have eyes, I've seen plants getting crowded by too-close neighbors that do better after weeding, but I've also seen plants that don't seem to mind crowding. I think I just need to learn more about who interacts and how.