Monday, April 7, 2014

Mallow weed, what’s it telling me?


In my last post I raved about how successfully I had planted out in the heat of February and I was so pleased at how healthy all the plants were looking. But while I was distracted preparing the March bed this bed became overrun with a weed, and the vegetables seem to have declined in health. I had never seen this particular weed in the vegetable patch before and became intrigued as to why it decided to all of a sudden start growing - in mass - in this one particular bed.

Despite gardeners being in constant battle with weeds, if you stop take a breath, calm the anger and hatred you feel towards them, you can often glean some valuable information from their mere presence. Well that’s what I am told. Weeds are meant to be excellent soil indicators. Simply by observing the most prevalent weeds you can deduce the quality and condition of the soil. They can tell you if the soil is too wet or too dry, whether the soil is healthy and balanced or depleted. They can even indicate if the soil is over rich or deficient in specific nutrients.

So what was this weed problem telling me?

Before I could conduct my investigation I needed to know ‘who’ I was dealing with. One of the best tools I find for identifying plants is Google’s image search. Search for an obvious characteristic, in this case leaf shape was the only one I could think of. I searched for ‘round leaf australian weed’. Surprisingly I recognized my weed quite quickly there on the first page, among many other “weed” images I recognised ;-)

Known for crimes in many countries my weeds name was: Small-flowered Mallow (Malva parviflora L.) belonging to the Malvaceae family, and going by many other names: Mallows, Marshmallow, Ringleaf Marshmallow, Whorled Mallow, and Whorlflower Mallow. Described as an erect or sprawling, annual or biennial herb to 1.5 metres with round lobed leaves, heart shaped cotyledons, small, 5-petalled white or pink flowers that swell into 4-10 mm fruits that look like tiny pumpkins.

Now that I had its name, the next step was to conduct a bit of research. Majority of online resources seemed to indicate that mallow enjoyed highly fertile soil. But like all the gardening research I do, why does it never turn out black and white? A few sources contradicted each other with claims ranging from wet to dry soil and cultivated to compacted soil. Like with all research it is important to compare what you read to your own experiences and observations. I have often seen mallow growing in my driveway, seeming it is gravel and highly compacted it seems to indicate it likes nutrient deficient, dry, and compact soil. I recently even saw it growing on gravelled road sides and walking trails. And growing in dry compacted soil does seem to make sense to it having a very deep tap root.

Turning back to the vegetable garden has me observing something quite different and very interesting: the mellow is only present in one isolated garden bed. So that got me thinking about what is different about this bed. Well… it is on the same irrigation system getting the same amount of water as all the other beds, it gets about the same amount of light, is on the same slope, and is prepared using the same method as the others. The only things different I can think of is that it has been recently cultivated by the chickens, and I added, as an experiment, two bags of commercial composted cow poo. This would concur with the majority of references claiming it thrives in rich fertile soil. And such a conclusion about my garden I am more than happy to accept.

There is also the other possibility that the mallow seeds were eaten by cows, and end up here in my garden. I do question whether this would be possible though. I would have thought commercial composting to be quite intense - killing off all seeds. But I am also open to accept that the soil is becoming compacted, or maybe I am over watering, or not enough.

Sadly understanding what this weed problem is telling me is not clear, but what I have learnt is that they need to go. Apparently mallow serves as a host for insect pests and viruses that cause diseases in neighbouring plants. One of the common pests it harbours is caterpillars. This clearly explains why so many of the plants in this bed are being eaten to shreds, particularly our precious kale needed for our morning smoothies. The good news is that they needn't go to waste. Apparently South African natives have used mallow for various medicinal reasons, including as an astringent, an anti-inflammatory and antiemetic agent, and a treatment for tapeworm. So following the advice that it makes a good alternative to spinach it has become a temporary substitute in our smoothies while the kale picks up.

Out of this research I came across this potentially valuable resource that may help with understanding other weed problems: weed and soil table

Do you get mallow in your garden, and if so under what conditions does it seem to thrive?

10 comments:

  1. Yes we do get this in the garden...but I never knew what it was called . Because we have chicken tractor beds, it never lasts too long in the garden and just ends up as chicken food as the chickens pen comes over it. I suspect it is a nitrogen lover as our beds have lots of chicken manure in them . I was thinking of liming our beds this Winter to see if that would make it drop back a little.

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    1. This seems to confirm that it likes fertile soil, and confirms my thought about the adding of cow manure having something to do with it.

      The adding lime comment has really got me thinking. As I use a chicken tractor also my garden is probably trends towards acidic. My soil would also be described as more clay than sand thus is naturally more acidic. I then went and add cow manurer (acidic) to possibly an already acidic soil. Opps! That could also explain why mallow likes my driveway, being clay it's acidic.

      Thanks so much for commenting Kim I think I will be getting soil test kit and depending on the results probably liming also.

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  2. Jason - greetings from Central Texas. I'm also wondering if your chickens might be "spreading" the seed for the mallow - it is quite popular with the white winged doves in our yard, perhaps for the caterpillar harboring tendencies but it could be the seed they are after. The bristly mallow in my beds is not competing with anything more valuable nearby and as you say has lovely tiny flowers, so I'm content to let it have its corner. That said I certainly wouldn't want it established in veggie boxes. Once the roots go deep it is reportedly difficult to eradicate. Here's hoping you've caught it in time and that your soil testing will help you decipher its message!

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    1. The chickens being responsible for spreading the seed is something I will ponder. My initial thought is: where would they be getting the seed from? You have me a little scarred saying that they are difficult to eradicate. Like you say I hope I have caught it in time.

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  3. Here in Alabama in the US, this stuff is trying to take over one corner of my yard. The chickens are around it all the time, but I have never noticed they had any preference for it. I have lived here for 45 years and have never used an herbicide, but this year I will to get rid of this weed and everything that is destroying my St. Augustine lawn. I would not mind losing the yard to food crops, but the weeds and wild onions make mowing it more often necessary. So, I can eat it? will eat some mallow before I spray.

    Thanks for that link to identify plants.

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  4. Sadly after you spray if the conditions of the soil don't change it may come back, time and time again. I am starting to think it is an indicator of acidic soil. Once you have gotten rid of it, try adding some lime.

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  5. Hi Jason, I'd see it as an indicator of acid soil, with too high a nitrogen for its own good. I think that's where the opinion that it likes "fertile" soil comes from, but high nitrogen is not necessarily fertile on its own. Chook manure, since they are birds, should raise the pH - chook manure is mildly alkaline. But the cow manure could be very acid. If it comes from yards or barn, it may well be urine soaked as well as poo. So I'd say you have a confused bed!

    I would get the pH up for starters with a sprinkle of agricultural lime or dolomite - dolomite if there are any signs of magnesium deficiency as well. You'll find good pictures if you google magnesium deficiency in plants. In general, it's yellowing of leaves with the veins still green, especially the older leaves. In the longer run, giving chooks shell grit will help. I roast and crush eggshells and use them in my potting mix too. And if you bring in compost or manure, go for bird manure by preference. But you may have to keep sprinkling gently with lime for a while to slowly change the profile.

    For the mallow, my chooks eat it, and it's an annual so if you've got onto it before seeding it shouldn't be hard to get rid of. I'd be careful about adding it to smoothies in bulk - a lot of medicinal plants aren't good for you overdone, and I know farmers hate it because it gives horses the "staggers".

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    1. Thanks for the great advice Linda. The plants don't seem to be suffering from magnesium deficiency as they are all very green. I have read to be careful using dolomite to correct pH as it has a bad calcium to magnesium ratio - too high in magnesium. I have started adding lime and giving the chooks shell grit. I will let you know how it goes.

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  6. Yes, I do get mallow and I get it most abundantly in the areas where I scatter its seeds.... ;) Turn your problem into a solution and start making mallow leaf salads. So much easier to grow than lettuce. Dry the leaves for tea, enjoy the pretty flowers. I try to encourage it to grow everywhere and I love it. :)

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    1. I love this kind of thinking Luise. It always amazes me what is available to eat.

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