Raised beds can be as complicated or as simple as the gardeners who cultivate them. Many just fill their beds with a simple potting or top soil and replenish them yearly with compost for nutrients. But if you live in a wet climate or experience a particularly intense wet season, you may need to make a few additional modifications to your soil. While wet climates are great at keeping plants from withering, they sometimes bring "too much of a good thing" in that they help fungus and mold grow over varieties that would prefer their surroundings to dry out occasionally.
pH: Determining What the "Best Soil" Will Look Like
Regardless of the climate you live in, it's important to determine what pH you want to achieve in your soil based on the plants you intend to grow. For blueberries, azaleas, and hydrangeas, the typical range of 6.0 to 7.5 is too basic. To add acidity to the soil, you can work in some sphagnum peat or mix a little vinegar into your watering can for a few days (only a couple of tablespoons per gallon of water).
On the other hand, cauliflower, cabbage, carnations, and lilacs tend to thrive in more alkaline soil. If these are the kinds of plants you want to grow (or if you want to grow any other plant that thrives in alkaline soil), consider mixing lime or wood ash into it.
Combating Soil Challenges in Wet Climates
In wetter climates, valuable nutrients tend to move around a lot and wash away quickly. Raised beds are already useful in some gardens for this reason, since the box and hardware cloth prevent your soil from seeping away or eroding into nothing. Adding more compost to your soil than usual is another make great modification to make here, as it will guarantee your plants a steady supply of nutrients.
Soil compaction is also a problem in wet climates. As water moves through your soil, it often tightens it down, effectively eliminating the airflow necessary for strong, healthy plants. You can handle this by both aerating the soil physically after a long spell of rain and improving the overall quality of your soil. For instance, too much clay can result in soil that's thick and airless by the end of the rainy season. Sand, gravel, and compost can all improve drainage and free up space for your plants' roots to thrive.
Lastly, poorly drained raised beds can present a problem in and of themselves. Ever noticed a spot in your garden that always seems to collect a puddle of water after a storm? This may be a sign that the ground is fully saturated with water and incapable of draining. When this happens, plants and their roots become more susceptible to mold. Even plants that love water are only equipped to handle moisture over relatively short periods of time. Luckily, the same additions of sand, gravel, and compost should also take care of this problem.
Mulching is another great way to combat these problems. Mulch of many kinds can help your soil withstand erosion and retain its nutrients after constant rain. To do double the good, look for a mulch material that will also work to help you achieve the ideal pH.
To recap: compost, mulch, gravel, and sand are all great options for wet climates. Asking a specialist at the local garden store can help you decide which one of these options is best for you, especially in relation to your specific selection of plants.
Regardless of which soil modifications you choose to make, you'll want to be sure to fill your raised beds with plants that can handle all the water that;s coming their way. Plants like bee balm and elephant ears are known for their ability to thrive in wet soil.
If your raised beds are specifically geared toward cool-climate vegetables, you may want to take a look at our guide to growing veggies in more bog-like environments. There are many things to consider beyond soil modifications when determining your best options as a gardener in a wet climate.