The 6" bed would be fine for annuals. You could put the perennials in the taller sections. Or, a cheaper alternative would be to improve the soil itself, then you won't need the raised beds. Perhaps you could borrow or rent a rototiller, rototill the area, and amend the soil with compost?

One suggestion if you go with the raised bed, make sure you have good drainage below the beds. Don't use plastic mulch. I would use many layers of newspaper. It is free, will smother the periwinkle and over time will break down and improve the soil.

Good luck with your project.

Thanks to everyone who answered. I think I'm going to put down a heavy layer of newspaper with topsoil on top of it and amend with compost and see where that takes me. It will definitely be cheaper, although it will take longer.

Put plenty of newspaper and cardboard down, but do not use top soil. It is too light and thin and there is not much nutrient value in it. I use the Sta Green flower and vegetable mix from Lowe's. It has a lot of organic matter and will not blow away like top soil.Everything I plant in there loves it!

Eventually, the worms and other micro organisms will eat through the newspaper and cardboard and the soil will be
full of nutrients!

I would not rototill though. The process of rototilling will destroy the soil structure already in place. All the micro-orgaqnisms and benefical bacteria will take longer to reach your raised bed. Not to mention, there will be some new weed seeds you bring up when you rototill.

Remember to mulch!!!!!

Hope this helps!

I just bought a bed like that myself. Haven't even put it together yet. I understand we can build the soil level higher than the 6" sides. That would increase the depth right away. Is that true?

Sometimes a garden fixture (statue, large pot, etc.) can make a rougher spot in the garden look more intriguing. Contrast can be a good thing.

Also, dead tree limbs and rocks can provide borders for a raised bed and look more natural. You can purchase firewood if necessary. The wood will eventually deteriorate. leaving the bed held in place by whatever you have planted.

Just a thought.

Be careful with using freshly cut firewood / treelimbs!!!!

As freshly cut wood deteriorates, if it is in contact with the soil, the decomposition process will actually steal the nitrogen from the soil! Thus making the said garden bed basically sterile.

In addition, termites could be a problem, so I would not use the limbs / branches near a dwelling.