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I have an elevated garden bed with some citrus trees. The problem is that the whole area is full of weeds (mostly a mix of crabgrass and dandelions) that are nearly as high as the fruit trees. Because it's elevated it's hard to mow. I've tried pulling them out, but they just grow back. I don't want to use herbicide near my fruit trees.

  1. How should I get rid of these weeds?
  2. How should I stop them coming back?

I've thought about laying carpet over them but apparently that can contaminate the soil. I'm interested in planting something to prevent regrowth, but I don't want to have to mow it.

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    Crabgrass and dandelions "nearly as high as the fruit trees"? – winwaed Sep 7 '11 at 13:45
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    @Coomie Is it possible to post a photo or two of the area "elevated garden bed with some citrus trees" you're talking about? Also where on the plant are you? ie General location so we know the growing conditions, environment... – Mike Perry Sep 7 '11 at 20:28
  • I think it's dandelions... They were around 170cm. I live in Western Australia (subtropical/temperate). I've managed to get them under control with the help of glyphosate based weed killer (roundup) and a line trimmer. I've planted grass which is growing nicely. I very selectively poison (with a jet rather than a spray) so as to avoid the trees and grass. – Coomie Feb 2 '12 at 9:13
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Start with some work with a scuffle hoe or similar hoe to remove the roots at the top. Rake off the cut material. You do not want to cut too deep and damage tree roots.

Then lay down superior grade landscape fabric. One or more layers depending on the weeds as bstpierre notes. In some parts of the country this will be called a woven geo-textile but result is the same. Water and air penetrate through the fabric but weeds will find it challenging to come up through it.

Top up with a mulch of your choice. Preferably not sawdust or other woody type material that will decompose quickly and use up nitrogen which your trees need. I like pea stone gravel, you may prefer to use locally available materials which do not degrade quickly.

Weeds will poke through wherever there are cuts or at the base of the trees but this is still much less work

  • I can't find a reference right now, but I've read that -- as long as it is on the surface and not mixed in -- the sawdust won't steal nitrogen from very far away in the soil. For this reason, wood chip mulch is probably a good choice. – bstpierre Dec 7 '11 at 16:39
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    I believe how much nitrogen would be used by decomposing sawdust would depend on the type of soil and amount of rain the area receives. Sawdust seems like the kind of mulch that would blow around so would not be my first choice. – kevinsky Dec 7 '11 at 17:08
  • Yes, I wouldn't choose sawdust, but chips would be good. I found a reference: "many studies have demonstrated that woody mulch materials increase nutrient levels in soils and/or associated plant foliage. My hypothesis is that a zone of nitrogen deficiency exists at the mulch/soil interface, inhibiting weed seed germination while having no influence upon established plant roots below the soil surface." (p3) – bstpierre Dec 7 '11 at 19:55
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I have recently acquired a weed torch, which allows me to kill weeds without chemicals. It is essentially a blow torch run by propane. I would recommend the same model I am using http://www.amazon.com/Red-Dragon-VT-2-23-000-BTU/dp/B00004Z2FP/ref=sr_1_2?ie=UTF8&qid=1315411041&sr=8-2

You have to be careful around the fruit trees, but the cone of heat is much smaller than you would think and it is pretty easy to clear the majority of the weeds this way. Just a few seconds and the weed shrivels and will die completely. It is really easy (and more than a little fun). I was worried about fire danger, but it has been incredibly easy to control so far.

This will not prevent them from growing back, but it would allow you to clear them easily and free of chemicals. You can then choose ground covers depending on the location and situation. There are a lot of live ground covers that don't require mowing, but the level of shade and moisture in the location will affect your choice. You can also use dead ground covers like redwood mulch.

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    I'm giving you a thumbs up because your answer is cool. But this isn't the best answer. – Coomie Sep 8 '11 at 0:43
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You probably have some other Asteraceae, many have flowers like dandelions (I don't think dandelions get that tall). If they have a long taproot they are bringing up nutrients from the subsoil.

Use a weed trimmer on your volunteer biota. Research companion plants for citrus if you want to change. There may be lower maintenance plants that can provide other ecosystem services such as nitrogen fixation or beneficial insect habitat. In any case there will be better soil water retention if there's have something growing on the soil. Go with your native ecosystem, not against it - use natives.

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Cardboard is my weed barrier of choice. I've been putting a little fresh compost just under the cardboard but only about an inch thick. Once the cardboard is in place then I'm covering it with wood chips from the various natural trees in the area. The compost helps to build the soil until the cardboard breaks down and the wood chips start to decompose. Next year you can put on a second layer. Not too difficult but it sure does control the weeds.

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I have been successfully using the cardboard, compost, mulch method for three years now. You do get an occasional weed come through, and in some places where there is particulary invasive grass you may have to mulch heavier. We put down cardboard, compost and mulch in Autumn and again in late spring. As you did down into it now it has decomposed very nicely and the soil is rich and dark and loamy, it makes an excellent growing medium, everything we've grown in it has been extremely vigorous. We use recycled cardboard from our retail jobs, saving our employers a lot in refuse fees. We compost our garden waste and food scraps and we have a worm bin for castings & worm tea. We buy bales of bean straw and barley straw from a nearby farm.

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Dandelions are a beneficial weed and will actually bring up nitrogen for your Citrus to use. Look up the positive effects of Dandelions. As long as you are not growing any type of leafy green that the Dandelion will overtake and push out, letting Dandelions grow around your trees and other shrubs, etc is actually beneficial and good for the soil. Plus you can eat the leaves. They actually have quite a lot of nutrients

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    Do you have any references for the positive effects of dandelions? – kevinsky May 24 '14 at 19:25
  • Like I said, other than looking bad in your grass or interfering with other leafy type vegetables by crowding them out, they are quite beneficial. Do a google search or check wikipedia...Its a well known fact. Dandelions are nothing new :-) Here is a start for beneficial weeds. en.wikipedia.org/wiki/Beneficial_weed – blazeaglory May 25 '14 at 3:52
  • Plus bee's use weeds and Dandelions as their go to for pollen. Thats is until suburban sprawl decided that weeds are a bad thing. – blazeaglory May 25 '14 at 3:59
  • Purslane is a great one as well. Its taproot drives deep and many vegetable plants will coil their roots around it. Dies every winter providing deep rot. Doesn't grow tall. And it's edible (though I haven't). Ime it can handle a nutrient-rich soil pretty handily, while many beneficial weeds struggle establish themselves. (Just my $0.02 on BWs) – Paul Nardini Mar 11 '17 at 13:35
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I would almost never recommend using landscape fabric in garden beds! All of the hardest, thickest and worst patches of weeds I have ever dealt with have one thing in common. That one thing is landscape fabric. Mulch on top of the fabric breaks down and creates compost for weeds to grow into. They sprout on top and grow roots through the fabric so when you go to pull them, they almost never come out clean. Trust me, it is a huge pain in the.. Not only that, but you are installing a barrier that will prevent soil building and the natural mingling of micro and macro organisms in your soil and the mulch layer. Not good for your trees! Then you have big chunks of black fabric surfacing from below the mulch in a year or so and it looks terrible. You can probably tell by now, but I hate landscape fabric with a passion! =] I will use it under pathways, patios, french drains and other places where I'm not growing things.

What I would do if I were you is this:

Use a string trimmer or something to cut the weeds down low to the ground. If there are seeds present, try to cut them off and discard them first. I would only really worry about especially rampant weed seeds in this scenario. Leave the clippings there. Take some plain brown cardboard or news paper and lay it over the weeds. If you have compost, put some compost over the cardboard. If not, just put whatever mulch of your choice on top. To prevent weeds, just add more compost or mulch every year to suppress weed seeds from germinating. That's it. Cardboard does the same work as landscape fabric, but it decomposes in about 6 months to a year, making it a much better alternative. This is called "sheet mulching" It's an easy way to establish new garden space or deal with really tough weed patches.

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