First, why would you want to try to grow vegetables in the shade? They need full sun. Second, putting 10" of soil on top of the root system of an established tree is almost certain death from suffocation. Try just the opposite. Build your raised beds between the driplines of the trees where they would get at least a few hours of sun each day.

Hi Aemon Sounds like you have done well...if your sleepers are not old ones...some of the old ones have been treated with creosote...another baddie Your mushroom composted soil sounds really good and I have one peice of advice which as is usual comes too late (if you did not think of it yourself) and that is to roughen up the surface of the clay by digging it over before putting the soil on top...the reason for this is because clay usually has a smooth surface and is not water absorbing...what happens is that when it rains or you water the topsoil the moisture that leeches down will reach the clay (where it is smooth) and it will run off because that is the way of least resistance...you will find seepage of highly nutritious blackish coloured liquid at some point...if you have dug over the clay so that you have a very rough surface it will prevent the leeching liquid from flowing and so it will soak into to the clay and enrich it with bacteria and soil fungus thus helping to created an even better soil...I am assuming you are on some sort of slope where you are cheers Peter Good luck

Peas are done. There were very few immature pods, and the plants were yellowing, so I yanked them up and got the rest of the pods. Not a bad harvest (Super Sugar Snap) over the last couple weeks, but it reminded me that the low yield of peas is barely worth the effort. Broccoli is toast. Between the heat and the striped worms, although I harvested all but one of the primary heads, and they were great, and the saltwater bath only brought a few worms out. The secondary smaller shoots were infested to the point where they were mostly inedible, but at least I got the primary heads before they really took hold. Thought about trying to baby the plants through and see how they did, but I almost think I'm better off yanking them, using that spot for something else, and then starting more seeds in July for a fall crop. My first planting of sweet corn is about 3' tall now, and the Trinity plants are just showing some tassels. Planted 4/30. Pole beans are blooming despite the weird curling and cupping of the leaves. I have harvested a couple peppers. Tomatoes have many green fruits, nothing ripe yet. I have a San marzano that is close. Yukon Gold potatoes are almost died back. The Purple Majesty plants are just yellowing a bit. Sweet Potatoes are plodding along, seem to be taking off of it now. Pumpkins and watermelons growing like mad, no fruit set yet. Zucchini has a single fruit set so far. onions are bulbing. I have watered, and we did finally get 3/4" of rain yesterday, (a moist upcoming weekend looks promising as well) the first decent rain of June. Still plenty of subsoil moisture thanks to the wet May, so trees and shrubs are fine, but I have had to water the veggies and flowers a bit .

Glad I found this article as I think I can really help as I have the exact opposite problems, severe Gulf Coast Sand. 1st, you get enough light, dappled light deep in the south is good. Direct sunlight down here just fries stuff. The problems your having are drainage related. Vine ripening vegtables "think tomatoe is more of a semi perinneal vegtable myself more so than a fruit", have a harder time without the light. You have that white swamp clay but it is usually VERY nutrient dense. Usually you need to figure out how to make that soluable to plants. How deep have you dug? I am guessing that 2 1/2 foot down you have a hardpan of clay, so the water doesn't really run off but its more like a swimming pool and that is likely 99% of your problem, but again its just a theoretical guess without being able to dig. The use of double wide "plantings back up to each other and a slightly wider path" traditional rows is every bit as effective as the new raised bed craze. I've done every kind of bed you can think of, I have reversed double wide rows where you plant on the low point to retain moisture because of wind/sandy soil. You should consider planting water loving vegtables and could probably really excel at winter vegtables like purple top, radishes, brussel sprouts, cabbage, lettuce, onion, leeks, etc. You would have a hard time with carrots, garlic, deep roots and or meteraniean climate. I also want to say what have you tried to grow. Tomatoes should never be the standard of a garden in the south. Ex I grow some tomatoes and they do well minus our infestations of hornworms "when they come its not worth the fight, but I let them eat "kill them manually", then what I did this week right before August is cut the tomatoe down to the base rather than pull because of the root structure. I've already gotten spring tomatoes but the tomatoes are already about 2 foot after looking like crap the last two months. I would rather have your soil than mine to boot, yes you heard that correctly. I might as well be in Arizona with salt spray off the Gulf. So you adapt, palms, kale, radishes, turnips, cover crops, sugarcane, peppers, lemongrass, in areas where I get bay salinity flooding. Yous should think of the oppostie, what needs H20. DON"T ADD SAND, you would likely make concrete, in fact if your thinking about that, try a very small spot like 2x2 first. ALWAYS do that when considering extreme measures. Mulch won't help you much because it will just keep stuff cool/damp/wet. I almost NEVER say that. I would try pontomac and a couple other Potatoe varities but I have NO doubt you would EXCEL at growing sweet potatoes because you can root the shoots in water. They grow in straight water like 10x faster than in ground. You seem to be on the right track of trying to get things many gardeners recommend like "just add compost bull and everything is okay". You don't likely need much fertilizer as clay soils tend to pack a lot". I would like to finish with use nature against nature. Change your thinking a little bit from the traditional corn and tomatoe, and think why not take advantage of the nutrients and saturated soil to have a semi hydroponic garden in your backyard. There is a guy on ebay right now selling purple sweet potatoe slips, you can get white, beaureguard, etc. and try out jerusalem artichoke. Again I think you might excel with potatoes and they may suck up some of that h20. we plant them alongside ponds in the country for fdeer plots and for us. Best of luck.