jared185
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raised garden bed advice needed

Hi I am new to gardening as some of you might already know from my other post on here. I have decided to go with a raised garden bed and im fonstructing it from concrete blocks with 4x10 dimensions. I was going to dig the area im putting it down an inch and put the block in and then concrete the block together with the concrete from a local hardware store that you mix. Now I was planning to put gravel in the bottom and about 8" of earthgro topsoil and earthgro manure mixed together. And I was planning on putting a seeper hose through it as well. Now here is my question is there anything else I should or need to do im planting vegetables so does this setup sound ok I already got the block and also the concrete.

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rainbowgardener
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Don't put gravel in the bottom. If your bed is only 8" high, the only way much will grow in it, is if it can put roots down in to the soil under the bed. Break up and loosen up the bottom well with fork and then put your topsoil + manure mixture on top of that.

I don't know about mortaring your blocks together, if they are solid concrete blocks. You want water to be able to seep out of your bed. You could mortar the blocks but be sure you leave some drainage holes. Or you can dry lay interlocking concrete blocks.

If you just have the one bed, I don't know why you would bother with seeper hose. Just water it. Keep it mulched and you won't have to water very often (maybe none if summer rains come).
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imafan26
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Dry laying blocks works fine. To help keep them in place use rebar and fill the holes with dirt. You can plant in the holes that way.

Water will easily pass between the blocks. I have seen gushers coming out of mine when it floods.

The blocks can shift over time. Mine got pushed by galangal roots.

When the blocks are dry laid you do not need a drainage layer, and you do want the roots to go down as far as they can.

As Rainbow said, you just have to loosen the soil at the bottom of the bed. The roots of the plants will eventually do the rest of the work.

For myself, I would also add some perlite or sand to the soil mix. I have clay soil and the perlite helps to keep it loose and aerated. It is hard to get sand here that is not beach sand, perlite is expensive but a lot lighter.

I use perlite instead of vermiculite, it is easier to get, a lot cheaper, and holds less water.

You can also add compost to boost the organic layer in the soil and that will also improve tilth and water holding capacity.

Mel's mix works well for new planting beds. 1/3 compost, 1/3 peat moss, 1/3 vermiculite.
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jared185
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How deep should bed be I also heard that if you didnt mortor the block t ogether that pests will grow between them and that I should have rock in the bottom so water can drain better

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hendi_alex
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I've used blocks before and didn't like leaving the tops open as grass grows through and into the beds, and weeds are more difficult to remove from these small openings. Personally, I would tend to fill the block with sand and just cap the holes with concrete mix. I like the rebar idea, to help keep the blocks in place.

I have beds with no more than 8 inches of soil on a concrete pad, and lots of plants grow just fine. Last year I grew cucumbers, arugula, lettuce, very vigorous okra over 8 feet tall, Swiss Chard, kale, radishes, and more in the beds. I've read quite a few places where 6-8 inches is not adequate. In my experience, that depth is not optimal, but gives quite good results with lots of veggies. That said, if invasive roots are not a problem, then I don't see any compelling reason to block the bottom of the bed from the native soil.

In planning the bed, you may want to give some thought as to how you will manage the skirt area boardering the bed. Perhaps just mowing and using a line trimmer will suit you. I prefer my borders to be more resistant to weeds and grass. Currently am mostly using high quality landscape fabric covered with gravel. Mulch works o.k. but must be removed and replaced every year or two in order to remain effective.
Eclectic gardening style, drawing from 45 years of interest and experience. Mostly plant in raised beds and containers primarily using intensive gardening techniques.
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imafan26
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It is true, grass does like to grow between the blocks unless you have a pathway around the bed that is kept clear. I had plastic mulch and gravel around the beds as a pathway around the bed.

I planted in the holes of the blocks so I gained extra planting space. It was harder to get into the bed because I am not a hurdler so I did end up putting deck planters on top of the blocks for containers in some sections. That way I could move them when I needed to get deeper into the bed. Mortaring or putting on caps work too.

I weed whack around everything and it hurt when the gravel flew around, so I changed the edge of the path to pavers. The grass does grow between the pavers, but i can lift them up since they are not mortared in and clean out under them. It also helps that I extended the mulch fabric beyond the pavers so if I catch it early enough, the grass is easy to pull out since it takes a while to root through the fabric.

The depth of the planter depends on how deep the roots of your plants are and how comfortable you like to be.

If your soil at the bottom of the bed is not rock or hard pan, the roots can get through it.

Some very deep rooted plants, the roots of burdock or parsnips that are very long are the only ones that will splay out like an octopus when it hits a hard layer. Most roots stay within two to three feet. even beets and radish roots start lifting out of the ground more than they go down.

If you build the bed up to a comfortable height, it is easier on the back to work it.
Happy gardening in Hawaii. Gardens are where people grow.

jared185
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Well I am planning on planting cabbage peas corn tomatos peppers (cayenne, green) potatos cantelope onions and cucumbers and strawberries althought I was thinking about potting the strawberries in a large container . So I think 8 inches would be fine but I can go deeper. Also I have lime but do I need any plant food or addatives

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hendi_alex
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"Also I have lime but do I need any plant food or addatives"

I use a concoction of cotton seed meal, kelp meal, blood meal, and bone meal for long term enrichment. For short term needs or to give a boost, I use osmocote or other slow release fertilizer.

Your original topsoil and manure mix may be fine starting out, but longer term you will have to develop some kind of enrichment strategy. For my vegetable beds, I use a varied approach, relying on compost, natural fertilizers, and slow release chemical fertilizer. From the plant's point of view and the quality of the produce, I doubt that the decision matters too much. From the point of view of the soil, IMO organic is superior.

I stay away from the blue goo type water soluble fertilizers and only use the cheap bagged fertilizers in very limited applications, but almost never in my veggie garden.
Last edited by hendi_alex on Sat Feb 23, 2013 3:38 am, edited 1 time in total.
Eclectic gardening style, drawing from 45 years of interest and experience. Mostly plant in raised beds and containers primarily using intensive gardening techniques.
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rainbowgardener
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cabbage peas corn tomatos peppers (cayenne, green) potatos cantelope onions and cucumbers

Cabbage and other greens are shallow rooted as are the corn and onions, but shallow rooted can mean roots a foot down.

Cantaloupe, squash, cucumbers, peppers grow roots 18 - 24" deep and need about 4 gallons of soil per plant

Tomatoes put down roots more than 2 feet when they can and need at least 5 gallons of soil per plant, preferably more.

Potatoes are generally grown in deep towers with more soil gradually added as the plant grows. When you plant the seed potato, the crop potatoes will grow between the seed potato and the surface of the dirt, so that needs to be very deep.

You really do not want rock at the bottom, you just want water to be able to drain out, so dry laying your blocks or leaving drainage holes in the mortar.Except for the shallow rooted things, your plants do need to root down in to the soil. I have raised beds on my concrete patio and I do grow tomatoes in them, but they are 20" deep. I don't know what kind of "pests" you think will be there if you don't mortar your blocks. My beds are wooden fence posts dry stacked. There may be things living in between the wood layers, but if so, I don't see them.

Imafan already described soil mixes. With topsoil and manure you are pretty good already, but some compost, or any organics you can add, would be helpful.
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jared185
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So let me ask this I should I till the soil below the garden then add the mixture of top soil/ manure on top of that. And I don't want to sound stupid but I am new to this, do you add more fertilizer on top of the bed after its planted and plants are growing.

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hendi_alex
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Don't know whether it is right of not, but we add chemical fertilizer on top of the soil, but when adding organic amendments, mix them into the top few inches of soil.

To till or not to till. I think that you will get various answers on that. My inclination would be to turn the soil and add longer lasting amendments to the underlying soil. But if the soil is very hard or dense, turning it could just form a basin that holds water and gets water logged. So if leaning toward tilling or turning the soil, you may have to let the soil type help indicate the final call.
Eclectic gardening style, drawing from 45 years of interest and experience. Mostly plant in raised beds and containers primarily using intensive gardening techniques.
Alex

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rainbowgardener
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Yeah, if you have very dense clay, you may just want to poke holes in it and fracture it with fork to make drainage channels.

After your plants have been growing for awhile, you may want to give them some kind of nutrition boost. I just use compost, which can be added any time in as much quantity as you want. I add compost before planting, mid-season and in the fall to enrich the soil for next year.

If you don't have a compost pile, the best thing you can do for your garden is start one! :)
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jared185
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Is there any way you could explain amendments to me like what brands what is it like soil liquids powders etc. And thank you for replies without this forum I would have been in trouble

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jal_ut
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The roots of most garden plants go deep. That is from 3 feet to 11 feet. It is not a good idea to put any barrier on the original ground. No matter what its composition, the roots will go down into it and acquire water and nutrients from these layers.

The two things most often in short supply in our gardens are water and nitrogen. "Amendments" are usually compounds that add nitrogen. There are other things that are sometimes added too, but nitrogen is the big one.

Manure, compost, and chemical fertilizers are some options. Mulch is good too and as it breaks down supplies some nitrogen to the soil. Mulch also helps to hold the water in the soil.
Gardening at 5000 feet elevation, zone 4/5 Northern Utah, Frost free from May 25 to September 8 +/-

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hendi_alex
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Amendments:

From previous post: I use a concoction of cotton seed meal, kelp meal, blood meal, and bone meal for long term enrichment. For short term needs or to give a boost, I use osmocote or other slow release fertilizer.

Amendments can also include lime if the soil is acid or sulfur if the soil is alkaline. We usually have to add a little lime each year because our rain is somewhat acidic. Out west lots of areas tend to have alkaline soil.

To me, amendments are anything that you add to the soil. So it could be perlite to help decrease water retention and increase air. It could be any kind of fertilizer or pH adjusting additive or any kind of organic matter.

Lowes carries a wide range of fertilizers both natural and chemical, different kinds of lime, and various organic additives like peat moss, manure, or mushroom compost.

I buy my kelp meal on line, but Home Depot claims to carry it. I ordered bulk cotton meal and bulk perlite from a local nursery.
Eclectic gardening style, drawing from 45 years of interest and experience. Mostly plant in raised beds and containers primarily using intensive gardening techniques.
Alex



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