Raised Flower Beds Over Concrete
by Jim Kieffer
(Council Bluffs, Iowa, USA)
QUESTION: The only space I have that is, sunlight-wise, suitable for growing roses in within a large walled in patio area.
My hope is to build two, thirty foot long raised beds that are two feet high and three feet in depth.
I read through your article on raised beds, but all comments about their benefits seem to be related to beds build on top of soil.
Would roses thrive in raised beds build on top of concrete?
Would it be better if I made them three feet deep?
I plan to install a drip irrigation system on a timer so they would be adequately watered and I will be using drainage tile to make sure the beds can drain.
Thank you and I look forward to hearing from you.ANSWER:
Thanks Jim, This is a very good post, and that's why I am building a page for my Rose Blog so others can benefit from this content.
You are very wise to consider drainage, because roses MUST have good drainage, and will die if left standing in soggy soil where water doesn't drain.
My answer is, yes, you can build a raised bed over concrete, but only if you drill holes in the bottom fronts and sides of the raised flower beds.
The holes should be large enough so water can drain out easily.
The drainage holes should also be placed about 8 inches apart.
To keep the soil from coming out, lay down some window-mesh at the bottom and lower sides, inside the raised beds.
This will also keep out "critters" from crawling inside.
I recommend you only use bagged soil for roses and flowers in your raised beds.
After planting, add a layer of mulch on top of the soil to conserve moisture.
If the beds are backed by a wall or fence, you should make the beds a bit wider than 2 feet, to accommodate the growing plants.
Making them three feet deep is perfect and will give the feeder roots enough room to grow.
Always remember, plants have to grow below, before they can grow above.
To be sure your plants have enough moisture at all times, use a Moisture Meter ($7.95) around your plants every so often.
It will go down to 1 foot deep and will give you a reading if the soil is wet, dry or moist. Be sure to use it around the plants, not just in the front.
Since you are installing a drip-irregation system, smart move, you would want to know if the drip system is giving adequate water to your plants.