In a narrow shaded area where drainage may be a problem, do plants help or hinder?

If it’s a shaded area, the plants may not have enough sun. You may need to choose plant varieties that can tolerate both shade and boggy conditions. It depends on the area, but I suspect if it’s already shaded, plants might not shade it appreciably more than it already is.

Are you talking about soggy soil or areas where water collects in puddles?

Some easy ground covers that seem to grow almost anywhere are vinca minor, galium (make your own May wine. It’s also know as Sweet Woodruff), forget-me-nots, lily-of-he-valley

Very few shrubs are happy in bogs.

@anartist: Can you take a picture?

In zone 5 and higher, varieties of of primrose love wet feet and bloom prettily in the spring as do wild yellow iris.

I planted several of the yellow irises at the edge of my pond and I now have dozens of them, as they spread happily and without cost to me.

@gailcalled and @laureth thank you for your suggestions. This is a narrow space between two buildings where full sun is one hour a day and where water pooled some before ground was leveled out. The previous gardener had managed to grow some very leggy aucubas and a camelia that finally bloomed plus some ground covers, lily-of-the-valley, violets, crocus and a few other things that were all lost when a benighted condominium board dug it up and cemented it with a drainpipe in it. I removed the cement and am trying to restore the garden. It is not boggy wet, justt a little wet when it rains heavily.

You’re much better off with the plants.

First, the plants’ roots improve the permeability of the soil. They provide thousands of channels for the water to work its way down. Having plants there will also encourage the presence of earthworms, which will provide yet more permeability.

Second, the water is drawn up into the plants’ leaves, where it’s more available for evaporation (through the process of transpiration )than if it were down in the soil. Think about it: All of that leaf surface area is probably thousands of times greater than the surface area of the soil itself. When the sun is shining on that patch, or when the air circulates over it, that’s that much more surface area from which evaporation can occur.

@thorninmud a very strange link you have there

Oops, sorry. That was for another Q. Here’s the article on transpiration.

If the ground id sogy, the best plants to grow there are reeds. Bamboos will also grow there but beware that they are invasive and are practically impossible to kill or remove if that ever becomes necessary. It is, in my considerable experience, almost impossible just using plants to make the soil less “dauby“and more permeable, as I have the problem for many years. Putting in a drain with drainage stones over the drainage pipe is a good way to go provided that it is special drainage pipe to start with and that it has a place to drain away to!