How to deal with garden drainage problems?

You know you have a drainage problem in your garden when heavy or even moderate rain leaves puddles that take forever to drain. Or you may find out, to your dismay, that under a few inches of okay soil in your yard is a stubborn layer of hardpan (most people discover this water-resistant barrier —often packed clay — when they dig a deeper-than-usual hole, say, for planting a big shrub or a tree).
Really damp areas (especially in humid periods or in shady spots) are slow to evaporate water, whether from rain or from your sprinkler. Then plant diseases can get begin, particularly on foliage. The answer here is to try to improve the air circulation: Prune overhanging growth and give individual plants more elbow room. And when you’re in charge of watering, supply it to the roots instead of allowing it to splash the entire plant. Obviously, bad drainage isn’t good for any garden plant, not just trees and shrubs. If you’re smart or lucky, you can deal with the problem before you plant or redo an area. Here are some options, from the simple to the high-tech:

• Try improving the soil. Dig in lots of organic matter. Soil with a high organic-matter content allows excess moisture to drain through while absorbing needed water. Sounds paradoxical, but it’s true. (For info on improving soil with compost, check out the earlier section titled “Compost: More than Just a Fertilizer.”)
• Build and garden in raised beds. You control the soil within, and thus it drains well and your plants are happy. Problem averted.
• Create a rain garden or a bog garden, and plant only water-loving plants. Water-loving trees and plants include maples, willows, astilbe, ferns, filipendula, beebalm, mint, various sorts of irises, and canna.
• Route water flow away from the garden area. Just get out there with a trowel or shovel and create some diversion channels. Of course, you don’t want to send the problem to another important part of the yard or foist unwanted, excess water on your neighbor. Send it down the driveway and on into the street, or into the gutter. This water needs to head for the storm drains. (If this plan isn’t practical, dig a hole nearby, fill it with gravel, and route the channel there.) Fertilizer runoff can harm rivers and streams, so if you use this technique, be especially careful that you don’t use excessive fertilizer and that you apply it at recommended times so the plants use the nutrients rapidly. See the earlier section “Facing the Fertilizer Facts” for info on proper application.
• Make a gravel channel. Follow the advice about rerouting water flow, but dig the channel somewhat deeper and fill it with crushed gravel or pebbles. You can hide it from view for some or all of its length by scooping a little soil over it. It’ll still do its job of slowly but surely taking the water away.
• Use perforated plastic pipes, lightly or deeply buried, to divert the water to where you want it to go. Home supply stores sell pipes specifically for this purpose. These pipes usually come in various forms and sizes of plastic; clay tiling is also available, but it’s too heavy and expensive for most homeowners.
• If the problem is severe and you can’t seem to solve it, drainage tiles, a French drain, or a curtain drain are options. Installing one of these systems can be a very expensive and involved process. Hire someone experienced to advise you, explain the options, and install.