PLoni said:... Within a month or so, especially after fall rains and now winter snow, the crowns of the shrubs appear to be below grade. In fact, several are now sitting in puddles (frozen) at the base of the trunk.
I don't know anything about how to raise up plants that were planted too deep, but you can lower the "water table" once the ground thaws ... if the slope allows it, and you're willing to do some digging.
(This idea assumes that the puddle is there because of bad drainage, not just because the soil is too frozen to allow water to flow away from the plants. A trench won't help frozen ground very much.)
Do you have a "low spot" or a downhill slope fairly near the drowning plants? Or even some spot where you know the drainage is good and fast? if you can lead the excess depth of water from the plantings to the low spot or good drain, your plants' crowns will no longer be below water.
(They would still be below grade, but if you needed to, maybe you could hoe soil away from the crowns instead of jacking up the plants. In other words, lower the water level and the soil level to meet the plants, instead of raising the plants to meet the soil.)
"Fairly near" means close enough that you could dig a slit trench from your plantings to the lower spot in your yard.
The bottom of the trench near the plantings needs to be
deeper than you want the "high water line" to be . The trench also needs to slope
uniformly down deeper until it reaches the low spot or downhill slope or drain (e.g. a French Drain).
That might be too far and too deep to dig easily, but remember that the trench can be just a slit as wide as a mattock blade, or hoe, or a sideways steel rake. Loosen the soil with a pick, mattock or shovel, then remove the soil with anything near the width of the slit trench.
Maybe this needs heavy clay soil to work well. My trenches have vertical walls and they stay sharp and un-crumbled for years. Like concrete drains.
Water will drain down from the crowns of the plants and into the trench near the plantings. Then it will run down the trench and away from the plantings.
If you only have a low spot, not a slope, the water will fill that low spot and only drain as fast as it can "perk" straight down.
Fancy people, or those who don't want a twisted ankle, might half-fill the trench with drainage gravel or small perforated pipe, then some filter cloth or landscape cloth, and lay some sod on top. I leave my narrow trenches open and fill the larger ones with large rocks. The narrow trenches quickly sprout grass which hides them and I "just know" to keep my ankles out of them. Of course, they do function as "wheelbarrow catchers". But no one will ever drive a car bomb across my yard!
There are fancy ways to make the floor of the trench dead level and steadily sloping. Instead of getting fancy, I wait for a heavy rain, and watch where the water backs up behind a high spot in the trench. Then I use a hoe or mattock or "Sharpshooter" spade to break the "dam" that was holding back water. That water rushes downhill and helps even out the floor of the trench or pinpoint the next-highest spot.
Wait for more rainwater to back up behind another high spot ... and remove that high spot also. Soon you have no more high spots, and silt has filled in any low spots.
For once, I use the easy and practical method in preference to Rube Goldberg methods like tight strings, levels, lasers or walking dividers.
