invasive tree roots in raised bed

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Old 12-04-19, 07:53 PM
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invasive tree roots in raised bed

Hello, was wondering about how people fight tree roots invading raised beds from nearby trees. My three beds are just outside of the dripline of the row of Monterey cypress trees, which, although quite ugly, are said to be good for stabilizing slopes. The beds are 2' above ground, have a layer of thick landscaping fabric stapled to the sides; after a year and a half two beds have a dense reddish network of cypress fibrous roots.

Would a 18"-deep barrier from the trees' side slow down the invasion? Or should it go deeper? I was thinking about digging a trench just outside the beds and use old plywood sheets as a barrier. Not sure though if this approach would be effective against the cypress root system.

Would appreciate any comment or suggestion. Best wishes, h.
 
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Old 12-05-19, 05:42 AM
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Chances are your will not be able to build any type of barrier that will completely stop the roots so I'd just get out there in the spring every 2-3 years and dig around the inside or outside and cut them off!
 
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Old 12-05-19, 07:31 AM
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Marq1, thank you for the response! Yes, this is pretty much my plan now: remove all the dirt, clean all the roots, patch and reinforce the fabric barrier at the bottom, put the dirt back. I've seen this product in the big box store called "root barrier" and been wondering how deep one has to install it to slow down the root invasion to the areas right behind it?
 
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Old 12-05-19, 07:43 AM
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You need a solid barrier. Your raised beds are very close to the trees and well within root range (as you already know). The roots will be strongly drawn to the nutrient soil and moisture in your garden so you need a pretty solid barrier. Permeable landscape fabric can only stop the small roots but the larger ones can easily poke through.

I would line the bottom of your beds with very thick plastic. It's sold as a barrier to contain bamboo. If you have any seams they must be well overlapped and bolted tightly together. You can also look for a plastics supplier in your area and buy HDPE and then cut it to size for the bottom of your beds. Extend the barrier out beyond the edge of your beds then fold the sides up and attach to the sides of your raised beds above grade. This of course means your raised beds will have drainage issues. You can drill holes every few inches in the sides of your bed for drainage but make sure they remain above ground so the roots don't find their way in and if they do they will be visible and easy to cut.

Or, just dig up your bed every season or every couple years and cut and remove the roots.
 
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Old 12-05-19, 09:37 AM
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Or, just dig up your bed every season or every couple years and cut and remove the roots.
That is what I was stating, just dig around the inside (or outside) every couple of years, leave the roots, they will decompose, nothing is going to stop the roots!
 
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Old 12-05-19, 08:58 PM
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Pilot, Marq, appreciate the comments. I know I'm not going to win this battle, however, now that I have exposed the landscaping fabric, I believe I might be able to somewhat slow down the cypress root invasion.

The first photo shows how dense the roots can get; second shows that the fabric is pretty efficient in blocking the roots as majority of them stay underneath; only a few shoots manage to go through the fabric -- in the third photo. The fourth photo shows that not a single root could get through two layers of the fabric after two seasons, which is almost two years; the arrows point to the overlap areas free of roots. Most of the roots inside the beds found their way through the sides as the fabric didn't go all the way up to the top of the beds.
 
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Old 12-06-19, 05:23 AM
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My three beds are just outside of the dripline of the row of Monterey cypress trees
Maybe it's time to move away from the trees?
 
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Old 12-06-19, 05:37 AM
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So harum, you asked how to stop the tree roots. We gave you advice and you just want to keep doing what you've been doing? Is that the purpose of your last post?
 
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Old 12-06-19, 06:54 AM
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Thank you again for the responses! Well, I'm trying to decide what would be a good plan. Digging up the beds every couple years and removing the roots might be a reasonable option, even more so if I use two layers of the landscaping fabric, which turns out might act similar to a solid barrier.
 
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Old 12-06-19, 10:20 AM
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Landscape fabric has the huge benefit of allowing drainage. And, if it can slow the roots down so you only have to dig it up every 3-5 years instead of every 1 or 2 years it might be a good, inexpensive option.
 
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Old 12-06-19, 09:04 PM
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Consider feeding and watering your trees outside the area of the raised beds. The trees are searching for nutrition - help them out elsewhere. This was a solution I used for a big tree near my raised beds in my previous home - advice given to me from a very wise old gardener.
 
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