Hello, we live in Milton, ON where we have a good sized backyard with most areas receiving sun. We grow a lot of vegetables and berries with a lot of success. That said, in one corner of our yard, encompassing an area of approx 30’x30′ we have a mature Silver Maple that blocks all sun below it and keeps the soil quite sandy. The area is in the North by North East corner of our yard with a fence on two sides. When we first moved in 4 years ago grass was patchy and brown under this tree so we tore up the grass and planted ferns, hostas, and box woods. All but one box wood died off by the fall of that year. I then put gravel down in one area to make a small sitting area but so many leaves fall from the tree that I end up raking up the gravel with the leaves in the autumn. I would be willing to convert the area to a rock garden or install something visually appealing if nothing will grow there but I thought I would get your ideas first.
Mature silver maples (Acer saccharinum) are, like most trees, greedy for moisture. They will suck it all up, as their intake roots are in the first 15 cm of the soil. So your trouble is not unusual. Also, mature trees cast shade, and that can be a lovely area to sit and while away the day. Of course, few plants will grow in dense shade, and have a hard time competing with the tree.
A little planning and alternative ideas are what is needed here – as long as the shade, leaf fall and poor moisture content is part of the plan.
As you’d noted, gravel did not work. Instead it may be prudent to find the flattest area around the tree, and place either natural flagstone or the many concrete flagstone look a-likes in the area to at least a 3.5 by 3.5m patio. If you can dig down at all, keep them flush with the soil. If not, dig as far as you can, then fill in the no more than 3cm gaps with soil. You can plant shade tolerant ground covers in between, such as periwinkle (Vinca minor) moneywort or creeping Jenny (Lysimachia nummularia). Keep them watered, and they will fill in the spaces, and can be lightly trod upon.
Add your lounges and table.
Meanwhile, aside from the boxwood (Buxus sp.), you did not say if the ferns and hostas were still thriving. Boxwood, despite being shade tolerant, aren’t drought tolerant and can’t compete with the tree, so it’s not surprising that the shuffled off their mortal coil. If the hostas and ferns are still about, add compost now, while they are still in a small size. Do this every year, as it will add nutrients and moisture. You don’t even have to dig it in. When the snouts of the hosta are up, and big enough, can be divided if easily dug out. Just chop the root ball with a sharp spade, and leave 3 snouts per new plant. If they are not easily dug, they can stay as is. Ferns find their own way with stolons underground. I am hoping that these plants with regular compost and added water, will spread and provide a background for what I am suggesting next. I do not recommend a rock garden. They are certainly drought tolerant, but will not thrive in shade. Almost all rockery plants need full sun.
The ferns provide green, and the hostas, if variegated especially with white, provide green and pull light under the tree. In front of the ferns and hostas, and next to your new patio, I recommend planting up, in containers. There are many types, tall, short, wide, narrow, boxes, rattan look, terracotta, glazed, wood, the list is endless. I would use planters that can stay out all winter, especially if there is not place indoors to store those that can be damaged by frost.
Inside those large planters, add specialized planter soil, and put in shade tolerant annuals and perennials for colour. Perennials include coral bells (Heuchera spp.), the moneywort I’d mentioned before, but this time they will hang down, and if your planter is big enough, hydrangeas in the Endless Summer group would provide punch. The annuals for shade include tuberous begonias, which come in multiple colours, trailing lobelia and the colours of the coleus (Solenostemon) these days will take your breath away. In a planter, plant densely, so there is little space between plants, plant short in front and taller in back. allow the trailers at the front to hang down. Keep planters watered well. Attractive planters look good from the house and while on your loungers.