raised bed planning

hi there-

i am planning a raised bed for my spring/summer project and was wondering if any of you could help me with a few questions. i tried to search just now, but i got a message that the search engine is offline...so sorry if this has been covered already. anyway, i plan to build raised beds with cedar timbers and fill with bedding mix. the area where i will build them is currently covered with bermuda grass. should i remove the bermuda first? right now it is dormant...would it be a good time to build the beds and just cover them up with 12" of bedding mix? or do i have to remove or kill the bermuda? also i was wondering if any kind of barrier would be necessary, or if i can just fill with bedding mix. and then there's mulch. i have read through a discussion of different mulches and remember that a lot of people really like pine straw. pine straw is not readily available in my area, but i can order it. it's twice the price of super-fine hardwood mulch that i can get though. and then i was wondering if it might be good to use cedar mulch since i'll be using cedar timbers. i just don't know but don't want to make a costly mistake. most of my experience is with regular hardwood mulch, and i have seen how it compacts and seems to form a barrier. i will be planting the beds with a variety of perennials that attract hummingbirds, butterflies, etc., and the bedding mix will be pH balanced. any advice is much appreciated! and i'll post pictures of progress if anyone is interested. thanks!

From what I've read, B. grass is pretty tenacious stuff, so I'll let others advise you in that area. It would seem that a spritz of round-up once it starts growing would lay it low, but ...?

Below is a picture of a raised bed soil that I made. It has no natural soil in it & is wonderfully alive & drains well. It is made from a combination of pine bark fines, sphagnum peat, Turface, crushed granite and coarse sand. It both drains & holds moisture very well & everything I plant in it does very well. Because of what it's made of, I suspect the pH is just south of 7, but since there are no growing problems, I'm not even curious. The photo is of a 5 year old soil.

I've never been happy with any results of using hardwood products in or on a soil. I prefer the conifer barks, both as soil components and as a mulch. I can expand if you wish. Recently, I was part of a panel discussion at a garden group meeting. One of the panelists cited a recent study on the use of natural mulch products. It appears that of all the mulches tested, plants growing under cypress mulch fared worst. It seems it has some sort of allelopathic effect. Pine and other conifer barks (no sapwood included) were found best.

Al

I planted my first Lasagna Garden this year and it's doing very well. It certainly was a lot easier than digging out all the grass. There is lots of information online about the process and I've even seen a couple of threads on DG about it in the past. The book author is Patricia Lanza. I didn't go through all the steps she outlines, but I did use a fairly thick layer of wet newspapers and then covered it with other good stuff. I immediately planted some winter plants (viola & pansies) and I haven't seen any sign of weeds yet, but of course, Spring will be the real judge there.

You don't have to worry about the grass. You can just lay down several layers of newspaper like teateacher says, or alternatively a single layer of cardboard from old boxes and cover it up with the material for your beds. Take the tape off of the boxes first, or it will work its way up to the surface forever.

I built a bed 200 x 50' around my GH by just laying down cardboard boxes and covering with 6-12 inches of horse manure. I let it sit for a year, and now the cardboard is gone and the plants grow like crazy. SB

Perhaps Burmuda grass behaves differently in MO but around here covering it up, even with heavy cardboard, won't even slow it down, nor will Round Up by itself. There is a chemical called Ornamec which is *somewhat* effective but you will still have to keep after it on a regular basis. Digging it by hand will be a chore as every time a bit of root is left in the soil it will sprout.
If you dig all you can, spray with Round Up AND cover with heavy cardboard you will at least have a fighting chance to stay ahead of it.
I have seen Burmuda grass come up through the pavement in the streets.

The heavy wet newspapers in Lanza's lasagna method held the Burmuda back for about 1 year for me. I used 5" of wet paper.

Thanks everyone for the advice. It would be easy enough to spray with roundup and lay down cardboard. stressbaby, thanks for the tip on the tape - I would not have bothered with it. As far as the soil, tapla, your soil sounds great - and hard work. I found some bedding mix available in my area that can deliver a truckload. I think I will go this route since I'll need to spend my time building the cedar container. Pine bark mulch would probably work well in this project since it would not be able to float out. I have not used pine bark before, but i'll consider it now.

Amber, my grass was not Bermuda...Ardesia sounds like s/he knows Bermuda better than I do. SB

I made a 6 ft. square strawberry pyramid one year and put down overlapped strips of roll roofing on the grass and filled with the good stuff. It was fine the first year. I picked a large cool whip bowl of berries every other day. Problems came in the 2nd year with the grass growing up through three layers of rows. I had to dismantle the entire thing the 3rd year because the grass runners that I tried to pull out were so long they couldn't be pulled out.

If I were you, I would get rid of the bermuda first.

Louise

Amber, that's a tough one. If you were growing annuals there I'd say leave the bermuda (well smothered) and grow your plants one year, then plant buckwheat, which is one of the cover crops that can help some with bermuda runners. Then annuals/veggies again. Then buckwheat.

Ok, well, maybe this just won't be easy. The last thing I want to do is disassemble the beds a few years later to deal with bermuda. I know about the hard work in removing bermuda - I put in a good-sized tropical bed last summer, just in the ground. I thought that if I built raised beds, it wouldn't be so much work. Now I'm sold on the idea of raised beds, but I guess I'll prepare as if in-ground, minus the extensive amendments. Well, I know what i'll be doing all spring and summer!

Al, I am curious about the hardwood mulch vs conifer and also the cypress having negative effects on plants. What are your onions of cocoa shell mulch? Always looking to learn. Thanks

Bill

Amber, we have Bermuda and love it but wanted to create a corner garden of raised beds and we sprayed the Bermuda with Ortho Weed & Grass Killer which costs about 13 bucks at Lowe's. Half of this 24 oz (concentrated) bottle killed the grass in the 20x40' area we needed and we topped it off with 3" of cedar mulch around all the beds made of Trex. We edged it all in with the commercial green edging and haven't had any Bermuda invasions the 6 months at least that it's been in. We've even had one of our warmest winters and were advised to keep watering lawns because the grass hadn't been able to go dormant.
Good luck with your raised beds! We love 'em.
Aimee

Amber,

I don't have Bermuda, i have salt grass, but i used the cardboard method and my beds were lovely the first year. The second year, there was some grass coming up through the layers (3) of cardboard, and 18" of soil. The third year the grass was completely back. We had to dig up an area (haven't gotten around to completely dismantling it yet) and the roots went down the 18" of soil through the cardboard (gone now) and down ANOTHER 9"! We are putting in a large raised bed veggie garden this spring so that our daughter who uses a wheelchair can reach in easily. The beds will be 24" deep over an area with much less grass. Because the last bed was such a disappointment, we are laying a 30'x30' cement pad, and putting the raised beds on top of that. No joke, it is the ONLY way to keep the grass out here. I put down some tar paper from a roofing job next door in one area of my garden, it took 6 months for the grass to come through... Maybe Bermuda is easier to kill, but if you want your bed to be long term, i suggest taking the extra time to make sure it is gone before putting your bed in.

Good luck, and Happy Gardening,
Melissa

I don't know how raised your beds are.. mine are in treated pine boxes about 2.5' high and filled with a huge variety of stuff- more of a random variety of soils that happened to be available, all well draining (lots of scoria, pumice and sand along with cactus soils, mulches, peat, manure etc.... mostly potting soil trucked in- not very scientific, that's for sure). And this all on top of a healthy bed of bermuda grass. Not thinking that bermuda grass would be able to climb up through over 2' of soil to reach the sky I wasn't too concerned.

But two things have occured- one is sinkage. The soil levels in the boxes have sunk over 6" in the last year, and the Bermuda grass did indeed make it's way up 2'... though only here and there (so far).

I have been knocking the bermuda grass back with round up and so far it hasn't been a huge problem (though as the planter gets more crowded, getting round up on JUST the bermuda grass is getting more challenging).

I emptied a few of the boxes of the current plants, and filled them with razor(also called feather) rock, more soil, and lots of perlite this time. Now we'll see how much more sinkage I get. As for Bermuda grass, it now has to climb up nearly 3' and so far hasn't...

this is one of 11 planter boxes in an early phase of progress. Anyone have any idea how long this treated pine might last?

I would guess that treated pine in your climate with a free draining mix and watering for cacti should last at least 20 years if it is 2x material. That ferocactus looks fun to replant. I've got a golden barrel that I have been putting off repotting for ages.

Palmbob, If your mix was high in organic matter, you might not be having as much sinkage as you thought, but more breakdown of the organics.

What a lovely set up you both have there!

So far I have gotten as far as designing the bed layout. I layed out twine on the grass and spray-painted the outline. Then on day right after it rained (it hardly ever rains anymore, it seems), I used a modifed hoe to scrape the outline of the beds into the ground, removing the grass layer. My hands hurt for a week! So much so that I am going to hire someone to build the beds and fill them up, then I will do the fun part of planting. I am really looking forward to what the plants can do in good soil! I'm not sure exactly what the soil details will be, but I won't cut corners, and will plan to add more soil as it settles. When I get a good progression of pictures, I'll post them.