You didn't mention adding soil. Are you growing in pure compost, or did you also add soil to the raised beds? And, do I understand you correctly that you put the hardware cloth down on top of your 'un-worked' native soil, then the cardboard, then the compost? If so, the cardboard will take a little time to decompose. A lot of people find it helpful to work (loosen) the native soil first, then build up.

It sounds as though the water is perching above the layer of cardboard. Presumably the water is draining through the cardboard eventually, although it may not do so at all if the native soil underneath is particularly impermeable. The cardboard also may not break down at all if it is buried 7.5 inches deep. What is the cardboard there for?

If you just planted seeds, or new plant starts, they will not be affected yet by the excess moisture that's 7+ inches down. It won't hurt them yet but they can't use it yet either. You need to keep watering at the surface to keep the new plants alive. But the issue of water moving down through the lower layers will need to be addressed eventually if it doesn't correct itself.

Those beds look huge (dimension wise). Hope you can reach all the necessary areas. Though I have to admit that's a great use for the shipping boxes.

Usually when doing the sheet mulching with cardboard or newspaper, you want to wet that layer down also. That helps start it going on decomposing, then add your next layers. Water will flow to down to there eventually, in enough amounts to help wet and decompose the boxes, but the water also can be tied up in the huge amount of soil that you have, wicking to all the different parts of the bed horizontally, too.

Seedling wise, they need water near the top of the soil, where their roots are. I would say to keep water them to keep them alive, and as theparsley said above, the soil down below being wet (along with the cardboard) should not necessarily impact the plants just yet.

The mulch has nothing to do with how well those beds drain. The cardboard can be what is stopping the water from flowing out, however. Until the cardboard is deteriorating it can hold an immense quantity of water. What you have created is very large containers with no drainage.

kimmq is kimmsr

I have, occasionally, seen instructions for raised bed construction that include a layer of cardboard at the bottom of the bed. But most will not advise it, and it may be counterproductive for drainage, as we are seeing.

If the purpose of the cardboard layer is to kill the grass and weeds underneath the raised bed, it's redundant and not needed at the bottom of a raised bed, because heaping a deep layer of soil on top of the grass and weeds will take care of that anyway. (It's not "mulch" if it's underground!)

There are differing opinions about whether you need to dig up and cultivate the soil underneath where the raised bed is going to be. I'm all in favor of labor-saving, but if the original soil underneath is heavy clay, or very compacted, it would probably be better to dig it up first instead of just plopping the raised bed on top.

I think eventually the cardboard should break down, if the soil in the raised bed is of a decent texture so that air can get through. (Cardboard buried between two layers of clay might in fact not break down, in the manner of newspapers preserved in a landfill.) The other good news is that capillary action works in all directions, so extra moisture in the raised bed will in fact move up somewhat through the soil as the surface layer dries out, instead of just staying right at the bottom over the cardboard. You will still need to water at the soil surface while the new seeds and plants are establishing themselves, but things should sort of even out over time.

Yeah, this will get better over time as the cardboard begins to decompose.

I have never used a moisture meter. I use my finger as a moisture meter. Which may be less scientific, but at least I am ahead of my dear other half who simply looks at the top of the soil, if she looks at all. The point is, use your senses and don't freak out about readings. If your tiny plants are dry, water them and don't worry about what's going on down below. When their roots reach that layer as it begins to get hot outside, they will be happy to dewater it for you.

The reason for using cardboard or newspaper, under a mulch is to provide a sun block for any plants that you do not want growing there, and with the use of less mulch. If the mulch, or soil, that is put down is more than about 4 inches there is no good reason to put a sun blocker down as well since that cover will do the job quite well.

Often someone will take a good idea and run with it without thinking out the whys and wherefores and use that good idea in ways not necessary.

kimmq is kimmsr

Regardless of whether the cardboard was needed or not, it would seem to me solutions are pretty simple to the perceived problem. Take some kind of spike or garden implement and punch a hole through the cardboard layer every couple of feet or so. It won't drain particularly fast but any excess water will likely find its way out in time. If you don't overdo it (violence or spacing wise), can't hurt. For an hour or two of relatively lazy work (spread it out over a couple of days if you like) will at least make you feel that it's not the cardboard. Only downside is it won't do much if the native soil doesn't drain decently to begin with.

I tend to agree more with toxcrusadr above, it'll likely be a non-problem soon enough. And I admit I didn't think about the hardware cloth, don't use it myself. But if concerned about the moisture, punching a few holes through cardboard won't take much effort. You could try in one bed to start to see if it makes a difference. But doing nothing will probably work pretty well too.

I'm curious what the hardware cloth was for. Burrowing critters?

If you are still reading I have n observation about Amazon boxes. I opened on up and put it in water to soak it because I wanted to tear it up to add to the compost pile. After six hours, I was able to pull apart the layers of the box, but within the sheets of cardboard it was still dry.

Twelve hours of soaking and I tore the sheets into about eights and found them still dry inside. At fifteen hours hours I toe the sheets into pieces abut four inches wide and found them still dry.

So I let it go to 24 hours and tore it up into even smaller pieces. The corrugated middle layer pieces were well wet, but I could hardly believe, the outer layer pieces still had dry spots. Tore it into yet smaller pieces.

I ended up letting it soak for 36 hours. Finally it was probably 95+% wet. But here and there I still found dryish spots. I tore it all up yet again and took it to the compost pile on this RAINY day.

Amazon boxes must be tough! I've used plenty of other boxes for sheet composting to start new beds, to put under wood chips when mulching against weeds in an ornamental garden, and to supplement the compost pile. But this has not been a "normal" box! I won't use one again like this.

If I were the owner of your new raised bed, I would be out there taking it apart to remove those Amazon boxes.

What is an Amazon box? Are you speaking of some ordered from amazon, the box it was mailed in? I don't shop on Amazon at all but I do save all my non coated boxes to use in my garden. Also brown bags and paper. I use them on paths under pots under beds and new plantings and in my compost pile. I have never had any issues and worms love cardboard. It will breakdown, unless you have found some super cardboard or went over board layering it 15 sheets deep or something. I have bindweed in my garden so when I got two raised beds last season I layered the cardboard and paper bags as much as I had as deep as I could, also trying to save money on soil. I still have bindweed I pull from the beds. It is the worst weed imo.

Gah, yeah, bindweed is my worst weed, too.

Yes, I was speaking of the boxes in which Amazon.com purchases are delivered, as I was original poster, I understand.

I, too, am big on using cardboard and paper, but perhaps this was the first Amazon box I've used that way. I don't usually soak them first, but wanted it to tear easily.

The only other box I remember causing problems was one I picked up in an ally next to a recycling dumpster. It had packaged a flat screen TV and had really thick corrugated cardboard in multiple layers. I used it in a problematic spot in my orchard to smother Bermuda grass, which it did underneath a layer of hay for one year and straw for two years. But I wanted that thing to break down, and finally after four years it is returned to the earth.