Raised borders

[Booldawg]

I'm going to be putting in raised borders with the intent of growing veg. The borders will be 9 inches deep and I'll be laying them on the lawn.

Is there a real need to turn the turf over where the borders are going to go? I should imagine the grass will die once covered by the borders and the veg roots will be able to grow through the dead turf layer (in a perfect world!)

[Clanad]

Nine inches deep is pretty minimal unless your interested in only shallow root crops and herbs. Salad greens, radishes, onions and th elike will do well, but if you wish to grow tomatos or especially potatoes, 12 to 16 inches or more is better.

As to your lawn grass... it will die out, but it will also present a problem if there are any weeds in it. Rhizomes and other creeping types of weeds will come up through your garden. Try this: see if you can either buy or borrow what we here in the U.S. call a potato fork. It's a pitchfork looking garden tool that has 4 or 5 times instead of the finer forks used for straw and hay. Use the fork to penetrate the lawn several times all along the length and breadth.. Step on it to insert the tines at least 4 or 5 inches. Then, having saved a goodly supply of newspapers, cover the entire lawn inside of your raised garden with several overlapping sheets... maybe 5 or 6. If it's windy soak them in a bucket of water first or just spray them with a lanw hose.
Then cover that with an inch or so of good organic materal like mixed loam and manure. You can buy sacks of irradiated manure at your garden store which kills the weed seeds.
Finally dump good soll in the structure. Mound it up in the middle since it will settle. In fact in succeeding years you'll have to add more soil.
We've built several over the years and really like them. You'll find that a width of about 4 feet works well. Ours are 20 feet long and are made of treated 2 X 8 lumber, one atop the other giving 16 inch depth. Don't use discarded railway ties... creosote is bad stuff. Lastly, be sure the treated lumber you use is not arsenic based...
Best of luck!

[carrust]

You'll also find that the soil will very compacted. I'd be tempted to single dig the areahttp://www.bbc.co.uk/gardening/basics/techniqu es/soil_digging2.shtml#simple_digging. This will also improve the drainage in the raised beds.

[Booldawg]

Thanks for all the helpful advice. Looks like I'll have to double up on the height!

[Clanad]

If you decide to double them up, see if your DIY store has steel fence posts. Here in the U.S., they're usually painted green, have one side that's flat and have a series of holde through them. The ones I use are about 4 feet in length. Once you get the bottom "box" constructed and in place, one can drive the posts very easily so as to be flush agains the bottom 2 X 8. Leaving about 8 inches exposed, the next 2 X 8 can then sit on top of the first. Coated deck screws about 2 inches in length can then easily be driven through the holes into the boards securing them against the outward pressure of the dirt you'll use to fill them.

In a twenty foot run, I use 4 per side and two at each end....

Again, best of luck!

[Booldawg]

I've managed to find some gravel boards (usually used to sit under fence panels) that are 3/4" wide x 9ft long and 6" inches high. If I use 3 layers then this will give me plenty of height.

I'm just a bit concerned about them rotting. The website says they are 'pressure treated' which means nothing to me!

I've also managed to find a local company that supplies a topsoil/manure mix. I'm hoping to get this done in February ready for planting in April.

Thanks again!

[Clanad]

Here in the U.S. there are two classes of pressure treated lumber. One is for general use out of doors while the other is approved for ground contact...

[Twenty20]

Can I ask why youre going to the bother of raised beds? Is the drainage that bad where youre intending to plant your veg?

You could just dig out the grass and dig in some well rotted down compost. If you wanted an edge between the veg plot and the grass you could use a line of old bricks or some edging wood.

Raised beds are a lot of work (and unnecessary expense) in most cases unless you have poor drainage.

[Booldawg]

TBH I've no idea; its mainly aesthetic. I'm aware that veg will grow in a well fed border regardless if its raised or not.

It will be slighlty easier to weed being raised and more manageable when it comes to cutting the lawn etc. Other than that I doubt it adds to the quality of the growing environment. There is an initial cost, true. This border will last for many a year and the cost is fairly neglible in terms of the enjoyment it will bring in creating home produce.