Killing weeds but saving tree

topic posted Fri, December 14, 2007 - 5:13 AM by  Alex
I've asked this question a couple of times, in response to similar posts, but have never gotten a complete answer.

We're wanting to rid our yard of grass and weeds, and eventually landscape with drought-resistant plants and trees. We can't do the landscaping right now, but don't want to have to deal with the grass and weeds, either. We've got one tree in the yard (mulberry) that is pretty water-needy, but it provides terrific shade for the front of the house. We'd like to keep it for now. We may remove it later and plant more drought-resistant trees in the front.

I'd like to lay down newspapers and mulch to kill off the grass and weeds, but still need to water this tree. We've got automatic sprinklers, but a dog we had for a while chewed some of the heads, and we haven't replaced them. We're just using a sprikler that attaches to a hose to water this tree.

Any suggestions on how to kill the grass but keep this tree alive would be greatly appreciated!
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  • Again, the newspaper DOES NOT prevent water from going into the ground as it normaly would. the paper prevents sunshine and CO2 from reaching the plants below, thus starving them in effect. you need 4-5 layers and enuf dirt or sand to hold them in place untill the watering bonds the layers togather.
    When you get ready to plant, put down "pre-emergance" to prevent seed growth, and till it all under. put in your plants and mulch. If you're going to gravel, or sand, you should usa a heavy contractors grade plastic underlayment.
    If you want to deepwater the Mulberry tree, dig or auger a hole to accomadate a 2-3" dia. pvc pipe about 2-3' long, near the drip line. Do to the depth of the hole, and disturbing the roots, renting an auger is best.
    To keep critters out, you have to use a removeable cap .Put a hose in on slow trickle for a couple of hours size of the tree, drainage ect. effect how often to water.
    For future tree planting, the pipe should be placed when planting the tree,. Just stick it in the hole with the tree. that's where the roots are at that point. water the first year like this. It causes the tap root to grow deeper so it is more drought and disease restant.
  • nature abhors a vacuum, so I'd suggest doing all your weed removals Just Before you replant and mulch. If you just leave a space devoid of grass & weeds, you'll just get grass & weeds again. black plastics are toxic and nasty and when applied in wet climates or seasons they can drown your soil and cause deep-seated fungal and rot issues, or tree death.
    • Unsu...
      That's interesting Chili. Plastic would quite reasonably have the same effect as piling on another two feet of dirt around the roots. The sterile soil is where he roots do their thing and the added soil would very effectively sterilize the soil beneath it.

      Except the roots wouldn't be able to grow up cause - - well the plastic would stop it.
      And it might encourage fungal activity.

      Maybe Round-Up is the best solution. It doesn't go in through the tree's roots. It enters the greenery of the weeds.
      • Unsu...
        I know that some trees react very badly to having additional dirt piled over their root zones - redwood and oak, and apple trees, definitely, it can kill them in short order. Anything that adds weight, like rocks, gravel -- same result. I don't know if this is a general rule for all trees. But I've always heard it's important to keep the original soil level on the trunk when planting any tree or shrub so I don't see why that would change later on.

        Also, I have heard again and again that it's a bad idea to "sprinkle" in a tree's root zone (which extends out to or past the extent of their foliage crown). Especially not on a several times a week basis like most lawn watering is done. This is because the roots go up to the surface and get very weak and thready; it affects the tree's stability and makes it even less drought-tolerant, encourages heart rot, etc. Deep, less frequent watering into a trench around the tree - using the rule of thumb that it takes 1" of water to water 12" of soil, so you want it to hold a decent bit in the trench - no more than weekly for a baby tree, and I'm sure less often for an adult tree - is considered the best way to go on all counts. Saves you water too.

        Then again, there are various weed killers that claim they will remove grassy-type weeds but not harm adjacent trees. This may be true, but it does have environmental consequences now finally acknowledged and proven.

        If you were to scrape bare the root zone area around the tree to clear the weeds, grasses, and then dig a 2-3"-deep trench around that cleared area for deep watering (with a hose, not a sprinkler, and confine your weed removal methods and sprinkling to the rest of the yard, I think you could solve all problems at once. You will have to re-clean the area under the tree a few times at first but in my experience the area gives up reasonably quickly and stays bare, especially if that round area isn't getting sprinkled.
        • >> Also, I have heard again and again that it's a bad idea to "sprinkle" in a tree's root zone (which extends out to or past the extent of their foliage crown). Especially not on a several times a week basis like most lawn watering is done.

          Actually, this is one of the reasons we are considering removing this tree and replacing it. In my searches for drought-resistant trees, I've found they usually don't like to be watered as regularly as a lawn. Since all the yards in my neighborhood where they've got mulberries also have lawns, I'm guessing this is one of those trees. We don't want a lawn, and don't want to put out the water that a lawn requires. (I don't care what kind of lawn you've got. We live in Phoenix, and any kind requires much more water than native plants do.)

          This is also my reasoning behind getting the tree spikes that water deep down. Less water on the surface = fewer roots up on the surface.
  • Is there a reason that landscape fabric isn't an option?
    • Unsu...
      I've done about every method mentioned... with fabric, plastic and newspapers you will always get grass and weed growth in the top couple inches of soil you add on top. There is no way to get around having to weed a couple times a year, even if you go the Roundup route, you will have to get your hands in there and dig out the dead weeds and ones it misses. If you accept that weeding is part of having a weed-free yard, then I'd recommend doing landscape fabric or newspapers with soil on top, your tree will be fine and you will minimize the amount of weeds. And then any weeds or grass that sprout in the top few inches of soil are really easy to pull (or Roundup, if you want to go that route, I admit to doing it sometimes).
      • Usa landscape fabric, don't put dirt on top of it. If aesthetics is a concern, use some wood chips or something decorative. If price is an issue, use black plastic for the larger areas, and use a smaller amount of landscape fabric around the base of the tree. Get rid of the sprinklers, you don't need a large spread for watering. A simple hose with no nossle on the end will water the tree (water will go through the landscape fabric.)

        Plants will not grow through black plastic or landscape cloth. Newspapers, you will have to put alot of something on top of them, or the slightest breeze will blow them away. They also only work for a short period of time before they start to break down and weeds grow through them (I did this on my front yard, wood chips on top, and I now have to be on top of spraying it with poison to keep the weeds down).

        I try and avoid using round up or poisons anywhere near anything I have living. Sure, a tree is big and can withstand alot of abuse, but round up is meant to kill roots, and putting it near the roots of the tree can't possibly make the tree happy.
        • >> Get rid of the sprinklers, you don't need a large spread for watering.

          We don't really want to have the sprinkler system there. It came with the house. And, we don't use it. But, I also don't want to have to dig it all up to get rid of it. Then again, if we till the yard three times, I'm thinking the sprinker system will get pretty well torn up. ;D

          Ultimately, I want to have some raised planter beds, where I plant more decorative plants, a tree or two (or three, depending on size) for shade, and the rest Arizona desert-landscaping. I'm planning on having some walking paths, so watering by hand won't be a problem. And, the front yard isn't sizable enough to complain about watering by hand, either. (At least, not for me. I'm sure lots of people would still complain. :D )
    • Well, I'm wanting to do an actual desert-type landscaping. Which would mean thinly scattered pea-size gravel and desert plants. But, since everyone for miles around seems to insist in a lawn, my yards going to still get grass. {sigh}

      Basically, I don't want to completely cover the dirt with another substrate. I'm not doing "urban desert landscaping," where people just dump gravel on their lot and call it landscaping. I've been out in the deserts of Arizona, and I want my yard to look native. I just want to try to get rid of the grass and weeds that are obviously already in the soil.

      Actually, I'm thinking the "turn the soil three times" method sounds like it would work wonderfully. We would just have to rent a tiller three times. But, our ground is terribly hard here (not sure if clay is in it or not, but it's not red -- just normal dirt-colored). Is there something I should add to the soil, like sand or something, when I till it under?
      • Alex, I live in California and have recently found out about a group called the California Native Plant Society. You don't live in Cali, but there may be some other organization. This group takes plants and propogates them and has little sales. The last sale I went to had all the plants sorted by neighborhoods and cities. The nice thing about this is that I was able to find some plants that not only are native to my area, but thrive under normal conditions. Of course, still going to take some time until the native plants I put down take over from the grass and red clover, but in the meantime, I've put down wood chips around them to keep them at bay.

        I'd suggest doing some more research. Finding out some native plants for your area (if there is no native plant society, I'm sure there are some nurseries that specialize in native plants). Also, google the term "xeriscape", and you'll find alot of resources on planting and landscaping that does not require any water (or only very little).
        • Aaron,

          Thanks for the suggestions. I've read quite a bit, and know about plants that are native to our area. They're not that common in your average landscaped yard, though! ;o) I'm just wanting to do it in an affordable way for us.

          First, I want to get rid of the weeds and grass in the dirt. Then, I'm thinking of sprinkling pea-size gravel around, so it's not just dirt. Then, we'll start adding native plants, one by one. But, we need to have a plan to start with.
          • If you don't have the western garden book, get it- it covers all climates on the west coast, and new mexico and arizona.

            I love your plan. It will sound like a great garden when you are done. If you are eventually going to use raised beds, just throw down landscaping fabric and cover with pea gravel or something more locally appropriate. It sounds like this will be a multi step project, so newspaper would only last a season or 2- not a couple of years. Landscaping fabric comes in different 'grades' now- 5 year, 10 year, 30 year- they are all porous and still allow water to percolate- it's not hardscape- and now there's even bio degradable durable paper based weed blocker:

  • Unsu...
    I would dig down half a foot and place landscaping plastic everywhere in the space you are working with except for a nice circle around the tree. Most weeds aren't resiliant enough to grow through plastic. Be obcessed with detail if you do all that digging. No little spaces at the edges that will be some weeds later. Then bury the plastic. If some more weeds grow up it is just the topsoil until it grows healthy.
    • weeds will grow in as little as half an inch of soil. putting soil on top of plastic is kinda silly. Not sure what kind of plants you'll be preventing by burying the plastic 6 inches in the ground. The point of the black plastic is that it goes on top of the soil and blocks all light. No light = no weeds. Landscape fabric does the same thing, but allows water to pass through it.
      • most landscape fabric recommends 2-3 inches of mulch on top.

        you can also use straight mulch- no fabric- but you need at least 4-6" of the stuff. and that's really expensive unless you get one of those free 30 yard landscaping ctrs they advertise on CL. Sometimes it's useful mulch, other times it;s diseased trees cut up with twigs and branches with not a lot of bark and trunk trimmings.
        • The reason they recommend putting mulch on top of it is A) it keeps it down, and from wind catching it and blowing it away. You can also buy Landscape Staples that will help for this and B) it looks ugly.

          I wouldn't recommend using gravel/rock, unless you are looking for a permanent solution. You can buy a nice decorative rock, or if you're on a budget, you can always get free mulch. Comes from the people who are constantly pruning trees and throwing them into the chipper. A friend got some free this way, but unfortunatly, they would only give him 20 yards of it. No less. I got about 2-3 yards from him, and he's been working through it for about 2 years, and is now down to a pile that is only 5 feet tall.

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