Depending on the plant, it might. I had a red maple that sent roots up through a drainage hole in a large pot and filled the entire pot with roots. But not all plants root quite so enthusiastically. My larger concern, since this is posted in the veggie gardening forum, would be access to the raised bed for harvest. My beds, which are about 4’ wide, need access from both sides in order for me to be able to plant and harvest, so access to the raised bed and trampling of plants in the ground would be of concern to me.

Not quite sure why you'd want to do this. As you'll just end up with your perimeter plants sharing root space with the raised bed plants, you might as well just pack them all together in the raised bed, to the detriment of everyone. Seems to me that if you have extra space around your raised bed, why not just widen it?

Her raised bed plants' roots are not reaching down two feet, so that's not a problem. In fact, I can't see any problem. Yes, your plant roots will seek optimum conditions. And you can snuggle your foot in between your lower plants, if you must, to work on the raised ones.

I don’t see a problem with it, but do keep in mind that raised bed could shade your plants heavily, particularly on a northern side. As Dan said, you could just extend out the beds.

I could not do this because our raised beds are on sheet rock. We live on a hill so my front garden is terraced, the raised beds in a dugout portion on top of pure Sheetrock feet from what was soil surface before.

That's a good point. If your raised bed is two feet high (the description wasn't clear - is that what you meant?), the perimeter plants probably won't share root space with the plants in the bed. And if the bed is really two feet high, it's got to have walls, and that's why expansion of the raised bed might be problematical. That would be a demolition and construction project.

But jacoblockcuff brings up another very good point. If your raised bed is that high, perimeter plants outside the borders won't get as much sun as those in the raised bed.

Now, if the raised bed has an impermeable bottom, like a plastic sheet, water and nutrients applied to the bed will migrate to the periphery, where the perimeter plants could make better use of them. So perimeter plants on the southern border of the raised bed might do quite well.

If you're thinking of growing between and around your raised beds it sounds to me like you're having second thoughts about growing in raised beds. If you have two foot high raised beds and two feet between them and removed the raised beds you could spread what fills the raised beds a foot high over the area. If you expanded you garden area to double you could dig in six inches into the ground in your new garden. Which sounds doable.

I only grow in the ground. I had been digging sand and peat into my clay, but recently decided to use only horse manure. I've been digging in twice about two inches on each dig. I have to use deer fences but find that growing in the ground gives you the flexibility to grow at the end of a row where it meets the fence. And you wouldn't have the problem with the bed structures shading garden space that you could grow in.

After digging in that much amendments the ground swells up at least six inches which gives you well drained soil down as much as 18 inches. That's figuring about a foot deep, the depth of the spade, and the 6 inches of fluffing. It's a lot of work digging the first pass but it's also a lot of work to build those raised beds and then you have to fill them with something.

"... will the roots of the plant on the outside perimeter of the bed at ground level, travel up and into the raised bed that's behind it? "

I need two more pieces of information to answer that question.:

1. How deep do the walls of the raised bed go?
2. What kind of plants will you put outside the walls?

It doesn't matter how tall the bed is, the barrier to the roots is how much structure is underground. If there is no structure underground then there is no barrier to roots. It will all look the same to them.

Now, most annual roots don't travel far, so annual flowers or vegetables won't have much impact. (And if the side of the bed goes down 4 inches or more, those roots will never move past it.) Perennials and shrubs are a completely different story. They have persistent and often more aggressive roots that may even want to travel and propagate the plant. They would need a barrier a foot down to keep them out of the bed - and even then may be able to burrow under it.

thank you for the helpful responses and information everyone.

my bed looks almost identical to the one attached.

as you can see, it is very narrow and there isn't much to plant inside the actual bed. I could do a demo and contruction project but I want to explore my options. I have other beds that don't look like that but I think I've gotten another information from you all where I can apply similar rooting information to those other examples to decide what to do. good points on the shading, I believe with that I will plant shade loving vegetables should I decide to go this route

Richard Brennan,

thank you for the response and great information that ive taken into account. the walls vary and range from 2-5 feet. I have some short and tall beds

there is actually no structure or barrier beneath. the cinder blocks just sit on the surface of the ground.

However, my big question here is even if there is no structure or barrier beneath the surface prevents the outside perimeter plants from invading inside the bed, wont the weight of the barrier(assuming its cinder blocks or something similarly heavy) deter the roots from wanting to root underneath the barrier because the soil directly underneath the cinder blocks is going to be compacted or inhospitable?

thanks again everyone and happy new year

That's actually more of a planter or trough than a raised bed. It is rather deep for the surface area and not a very efficient use of the space. I'm wondering what the thinking was behind its design since there appears to be ample space there? Is yours mortared together? If not, my personal inclination would be to disassemble it and create a much larger but shallower bed. Or not make a raised bed at all.

Maybe instead of a tear down.. add on? If you are considering using the footspace at all, might as well dedicate it.

Build a lower tier of box around the edge of the existing walls to make an additional square footish sized planting space. Or perhaps use pots or containers around it. Some plants can like a bit of shade on their pots if their green bits clear the wall nicely.

You can grow stuff that can get sprawly, like squashes and bush beans, veggies that get snacked on by ground critters, low growers like lettuces and herbs, and root veggies in the current planters. A bunch of stuff can grow well in containers.

Well, if we're into demolition and construction, I agree that expanding that bed/planter looks like a good bet. Just add a few more concrete blocks at the ends to make it twice or three times as wide, and move one wall. That is, instead of planting outside the raised bed, just plant in an expanded bed. I don't see any mortar, so it looks to me just like stacked blocks. So "demolition" would just be about lifting. In fact, I'd just make it one block high. Not two. Probably don't need to buy any more blocks!

Very narrow highly raised containers/beds in a hot climate are problematical. The sun shines hard on one side, and heats up the whole thing. I had a bed that looked something like that (about half the width), but made of brick, and the soil temperature in the summer was astronomical. Never could grow anything in it.

floral, agreed. very inefficient use of space. interesting comment about it being a planter as opposed to a raised bed based on surface area to depth. what kind of surface area to depth ratio would you expect at a minimum for something to be considered a raised bed instead of a planter

dan, thanks for the note on the extra high beds getting overly heated in the summer. what did you eventually do with the bed? I wonder if insulating it during the summer could have helped in some way temporarily or maybe even painting it a lighter color so its not absorbing as much heat as a deep red typical of most brick?

ill probably take everyones advice and just tear it down. still appreciative of the responses in this thread because it cleared up some learning questions I had about general root growth. however I have one add on question to those that stated that roots at the ground level would invade into the elevated soil in the beds. I did a google search and some reading and came across gravitropism and from my superficial understanding of it, roots will usually grown downwards if they can. if that's the case, am I assuming correctly that the ground level plants roots can still grow UPWARD into the bed but it would take a bit more effort and energy then if they had a free path to grow downward? basically their preference is to grown downward but if there is luscious soil and moisture in a more unconventional area then these roots will go out of their normal path to access those?

Good point about gravotropism, but I think that roots will seek out water and nutrients. Gravotropism is helpful when a seed germinates. With soil above and below, the roots know which way is "down".

By all means make use of the concrete blocks. Make a large raised bed that is surrounded by a single layer of blocks.

My brick bed? It was about 6x1 foot x 3 foot high, and designed into the house. I ended up just keeping nothing in it except decorative rocks. In a hot climate, soil is a terrific thermal sink. The better connected your bed is to the ground, the less it will heat up. Of course, in a cold climate, a high raised bed will just freeze all the roots in the winter. So I can't see that there are any advantages to such a high bed.

For me a raised bed could be no more than 8 inches high, for stuff like lettuces, providing it was on the native soil. Maybe taller if you're growing roots. A single row of blocks would be ample. Personally I just grow in the native ground in beds which are raised by default through long use and addition of organic batter.

I"m sure gravotropism is real but some plants are far more aggressive in growing to anywhere they find the water and nutrients they need, and sometimes seemingly wherever there is just less competition. We've a lot of maples in and near our yard, they'll grow out roots and shoots out and up into just about anything - they love compost piles and piles of leaves, and will grow straight down, around and into a sandbox. FWIW. I just pull them up although they're a bit annoying when trying to turn piles of leaves.

with something that tall, you could turn it into more of a decoration, by also adding in a lower section. Now you have a larger growing space, and it give the area some appeal by having some things growing up on a higher level than other plants on the lower level. Eg, I could imagine that the top area would be nice with some kind of plant that hangs out over the top lip, flowing into the bottom one (but not taking up space there, since you want to grow other things on the bottom section also).