Hi,
I see you're in PA, maybe it's still frozen at the bottom.
Dig down to the bottom and see. If that's the problem? Then it will fix it's self.
got my fingers crossed for you. lol
:)Laura

Are you sure it's "compacted" and not just showing the effects of a hydrophobic crust that repels water for a time? The answer to that is to water twice. The first time to break the tendency of peat and compost to repel water when they dry down to less than 30% moisture content and the second time to allow water to seep into the soil.

Al

Strange question : Do the beds have a concrete bottom? - probably not but who knows- maybe more drainage holes on the sides are needed or they need to be cleaned out.

If you are talking about later on in the season, I think that tapla is right. I have the same problem during the summer - it does not rain much for months ( strangely the ones which you can grow most vegetables) here. I have a drip irrigation system for many of my shrubs but seem to prefer wrestling with hoses and hefting bucket loads of water for my vegetable garden for some reason. This year I hope that I can finish putting in some more effort up front to add a drip system for the veg garden.

If I do add something to a bed it is either homemade compost, bought compost (which has a lot of sand here), composted bark fines ( they look dark brown), or peat moss (which is cheaper) - they all donÂt receive water that well after being sun baked, it takes time to rewet them.

Another thing that you could consider is a layer of mulch which could keep the soil surface moist.

Best of luck to you.

I'd like to re-visit this thread. I have a raised bed about 6" tall with raised bed soil from Miracle-gro. It was a wet summer last year, and I note when i dug about 6-8" deep, the soil was damp and cool, which really did no favors for my chili peppers.

The only thing I can think of is there is a ton of ledge in my back yard, perhaps 2-3 feet deep below the surface (my yard is a flat spot on a hill). If the ledge is causing drainage issues, is there anything else I can do?

Generally raised beds drain very well, due to the simple fact that the soil in them is elevated and regardless of what the base material may be. But I'd suspect your soil is to blame - Miracle Gro soil products are notorious for being excessively water retentive. You can add some coarse organic matter - like compost - to improve drainage.

I have been reading about Perched Water Tables from Tapla. I'm wondering if I did not adequately mix the miracle-gro mix with the existing topsoil below. That being said I agree with you, the mix itself is probably poor drainage to begin with.

Most of the Miracle Gro products contain nothing but organic matter. It's usually "partially decomposed forest products" and poultry manure. I think mixing it with the native soil is a good idea. I guess though, that depends on the make-up of your soil.

In all that reading you did...was there any discussion of texture, particle size, bagged soils in general as being generally horrible at hydrology?

I can solve all your drainage problems with a couple bags of pine bark. I can't solve the temps...but a small cold frame hoop house can.

Basically a raised bed in contact with the ground is not a pot or a container, and should have a soil mix with both organic matter and mineral soil. MG unfortunately markets what should be a soil amendment, as 'soil'. Don't feel bad, a lot of people buy it.

If the MG soil is nearly all organic matter, it seems like adding bark chips is not the best as far as balancing the organic vs. mineral balance of the soil. Not arguing about whether it would improve drainage, you understand.

I too would recommend digging down and blending in some native soil. If you want the bed higher, you could bring in some topsoil and mix it in too. Actually an all-organic 'soil' will decompose over time and shrink anyway, so you might need to.

What you want in the end is mineral soil with plenty of organic matter and nutrients in it, not a potting mix.

I agree toxcrusadr. I don't want a flower pot soil for my garden, but a deeper mix of the original soil with an amendment of , well, good organic and mineral amendments...making a deeper mix of it all.

Well, I thought what I was buying was appropriate, as it was specifically called Miracle Gro "Raised Bed" soil.

And that is entirely understandable :-)) Especially since MG has such a huge television and publication presence. But most experienced gardeners will have a more realistic assessment of the product and can provide you better information to take forward to improve your future gardening success. And isn't that why you posted here??

It's not that it's not 'appropriate', it's just that Miracle Gro bagged 'soils' are notorious for such problems. In fact, most of the bagged products found have similar problems. What these companies have done is found a market for the waste of other industries (which is usually a good thing.) However, there is little investment into making a well-performing product. Rather, it's all profit with no input. The 'partially decomposed forest products' come from wood and lumber manufacturing, and the poultry manure... well, you get it...

Now, on their own, there is absolutely nothing wrong with the decomposed wood, or the poultry manure. The problem is that they are amendments, not 'soils'. Both are extremely moisture-retentive, and tend to compact. Once that happens, they no longer have air pockets and become deficient in oxygen.

As Wayne mentioned earlier, it's not simply that they are organic matter, it's that they have no appreciative amount of ingredients for 'texture'... or 'grit'. Pine bark (and other products) can help because it doesn't breakdown as readily as other wood-based materials, and supplies the texture required for movement of water (drainage), and air flow (breath-ability).

In any case, it's not really your (the consumer's) fault, the manufacturer doesn't see the need to inform the user of the issues at hand. They pretty much have a lock on the amateur bagged-garden-product market.

I've become so frustrated with store-bought products that I now make my own transplant medium from scratch. I could buy a professional mix, but it's not as cheap as the bagged products... and besides, mine - aside from a little work throughout the year - is free.

As was said earlier, shovel some of that stuff out of the bed onto a tarp or something, dig down into your soil some, and blend it back in. I think you'll be a lot more satisfied with the bed's performance.

Whether or not you should incorporate some of your RB soil into the native soil under the bed depends on what's under the bed. If it's clay soil, it's not a good idea to incorporate OM into the native soil under the bed because you will be creating the bathtub effect, which will happen over time naturally, but there is no sense in hastening the process unless you have a way to drain water from the subsoil ..... like tiles, French drain, sump .....

Too, learning the hard way via the "experience" of getting bit on the butt by our own mistakes isn't the best way to learn; it's an unnecessarily painful and tough way to learn. Instead, learn all you can, and employ your "experience" as a way to validate what you've already learned. You'll leave the trial & error guys standing in your slipstream.

Finally, you can use materials in RBs that are so water-retentive they would never fly in containers. With the earth acting as a giant wick, even the most water retentive media will drain well in RBs. Water will only perch in RBs if the particle size of the material below the beds is at least 2.1x the size of the particles in the over-layer.

Al

Al, I don't understand your statement here: "Water will only perch in RBs if the particle size of the material below the beds is at least 2.1x the size of the particles in the over-layer." I thought with particle size, the smaller it gets, the more water retentive it is. Aren't you saying the deeper soil below the raised bed, if it is 2.1x the particle size of the RB soil, it will have more water retentive problems? That doesn't make sense. The larger article size would make the water run through similarly to your own Gritty Mix.

^^ I agree. If there's clay underneath, drainage will not be as good, but if there's sand, it will drain like crazy. Seems like it anyway.

If there is clay beneath the beds, the problem is percolation, not perching. They're very different, even if the effect is very similar or the same. Salvation comes in the fact that water from raised beds resting on clay really isn't perched, so it's free to move laterally across the surface of the clay soil and evaporate rather quickly. This is also why RBs should be built on top of clay that hasn't been amended - to increase the amount of time before the 'bathtub effect' naturally occurs, as it will.

If you have coarse sand/gravel as the natural substrate and build a raised bed filled with a peaty mix, you get perched water. If the natural substrate is fine sand, you get good drainage (except for the perched water the fine sand holds). That water moves through sand fairly quickly doesn't mean the sand drains well, because it can retain a lot of perched water. If the substrate is clay, water WANTS to move downward, but it is blocked from doing so because the particles are packed so tightly together. Most perched water occurs in natural soils when a layer of clay or silt rests above coarse sand/gravel.

A medium with fine particles, whether above or below another layer of coarser material will always have more capillary 'pull'.

Al

Your comment I was responding to you mention the soil particles below the rb was 2.1x the size. I would think that would drain better than if it were smaller particles no? Clay is smaller particles no ?

A question about hard pan, would that also create the bath tub effect? I have crap builders fill hard pan, and for the last year I just dumped 6 inches of mulch to lay fallow on an area I want to plant banana trees in now. Do you are a problem with that?

The sum of water's adhesive bond to soil particles and it's cohesive bond to itself = capillarity. In order for water to move downward, gravitational flow potential (GFP) must be greater than the forces that make up capillarity. If it is not, water perches in the soil. Adhesion, and therefore capillarity, is directly related to the total surface area of the soil particles. The smaller the particles in any given volume of soil, the greater are the forces of adhesion and capillarity. A fine substrate under coarser substrate causes more water to drain from the coarser substrate above because of its greater capillary 'pull'. When soils are layered so you have a coarse substrate under a fine layer of soil. It's capillary pull is much weaker than the that of a fine substrate, which is what enables soils to more readily overcome water's GFP, which is is the basic outline of why we have perched water tables in pots when using media based on fine material.

Example: If you have a 3" layer of BBs in a pot and add a 10" layer of finer soil that supports 4" of perched water. You end up with 3" of BBS with large air spaces completely devoid of water except where the particles contact each other and what exists in vapor form and a microscopically thin film of water on the BBs' surface, then 4" of completely saturated soil (perched water) in the strata immediately above the BBs, then 6" of soil above the perched water that is more or less hospitable to roots.

You missed the part about clay causing a percolation problem - not a perching problem, though the effect on plants is roughly the same. A clay layer below your beds is like a pot w/o a drain hole. You can fill the pot with marbles and water (imagine how well THAT should drain), but the water goes nowhere w/o a drain hole (which would be equivalent to percolation in open ground).

In open ground, when water can percolate through the soil, small particles below coarse enhances drainage. A layer of large particles at least 2.1X as large as those in the finer soil above causes water to perch. How much water perches depends on several factors, but primarily on how much greater the soil's capillary attraction is than water's GFP.

Al

Well, soil organisms are going to relocate a volume of organic material that will amend the clay in the near vicinity of your bed, and especially directly underneath it. This may happen slowly at first, but as time goes on and as long as a significant amount of organic material is available in the beds, the rate at which the soil changes will increase. Unless you have a ditch, tile, sump, French drain, or other ways of directing excess water away from your beds, the modified soil will have more air spaces than the surrounding clay, and they will fill with water every time it rains. If water from directly above doesn't fill the 'tub', water will move laterally through the clay and fill it. This is why new raised beds should be built above unamended clay, and why it's counter-productive to amend the clay substrata unless you have made provisions for moving the water that will tend to collect in the amended soil.

Clay has a very strong capillary 'pull'. So water in your RB's soil will be pulled across the top of the soil and away from the beds where it will very quickly evaporate. You don't want it to migrate into the soil and get hung up there unless you can remove it, preferably passively, to prevent the hang-up.

Al

The really cool thing would be when you have clay soil without much organic matter, and you double dig your beds - amending them throughout the entire depth with organic matter/materials - then, unless you live in rain forest conditions (where the whole tub would fill daily,) you'd have a good depth of water from which to draw. Amending them throughout that double-dug depth would mean a consistent medium. Gravity would then draw the water down to the bottom of the 'bathtub'. Your plants would then have a reservoir of water throughout a dry summer where lateral movement of water would keep your plants happily irrigated, and if this bathtub ever did cause a problem, you'd see signs of root zone oxygen deprivation instead of wilting from lack of moisture.

Now... I've been gardening in amended clay soil for many, many years. When preparing beds, and turning in my amendments, I routinely dig down to the bottom of my double-dug depth. It all sounds good on paper, but not once have I encountered a perched water level. Why? Because there are many, many other processes going on in soil that do not occur in containers. The soil biome is an active, living ecology that behaves very differently than the controlled and limited environments of containers.

That having been said: I don't garden in walled, raised beds. Mine are raised from the simple action of loosening the compaction of the clay through turning/tilling, and by adding amendments. Perhaps a walled, raised bed behaves differently, but I'll let you know - both through trial and error, and understanding the soil-science of adding organic matter to clay - when I encounter a perched water table in soil. In fact, in my climate of E. Tn., I'd be happy if water/moisture collected in my beds. One of the primary reasons for adding organic matter (both blended into the clay, and as a mulch) is to retain moisture and slow evaporation.

After reading through my response (which was written after a long day by a very tired body and mind,) I should note that I am not trying to refute Al's points. My goal was to add that real world experiences have varied factors at work. Al's descriptions of the physical principles under which water behaves is completely sound. One ignores physics at their own risk. However, when we work with those principles in mind, we can compensate appropriately.

Just as an example... when discussing capillary action and the percolation problems of clay, one should keep in mind that not all circumstances are the same. If, for example, the clay substrate is moist, but not saturated, it too has capillary pull. That capillary pull can add the the effects of gravity and help wick water downward. If though, one's use of a rotary tiller has 'smeared' the clay, aligning it's structure into a smooth surface, water will not be quick to pass through the barrier.

Outside the lab, some gardens have a slight slope. Drainage will be better under such conditions. Terraces are great examples.

Also, not all clay is created equal. Some clay will drain better than other clay. And... if you have bedrock within the drainage range, all bets are off.

Reading through this thread makes me question my approach to my raised beds. What would be the best thing to put in a raised bed that sits on top of clay soil? I put in four 8x4x 6inch raised beds. Due to the weather, I was only able to get two done where I dug one shovel depth deep of the clay, broke it up, and mixed with composted yard wastes (Leafgro). Now, I still have 2 beds that need to be completed (I removed the grass already, however, and the beds now sit a little below the surrounding ground). What would you suggest I use to fill them up? I live Southeastern PA. I intend on using the beds to grow vegetables and herbs. The beds are on a hill that slopes slightly...not sure if that makes a difference.