Caroline Lewis is a Portland, Oregon, urban gardener whose company, Verdura Culinary Gardens, is dedicated to helping gardeners be more successful at raising their own organic vegetables. A licensed landscape contractor, Verdura installs raised bed gardens including trellises and drip irrigation systems, creates custom year-round planting plans, and offers vegetable garden coaching and maintenance programs. Caroline welcomes your comments and can be reached at caroline [at] verduragardens.com.
If you are (or aspire to be) a vegetable gardener, you have likely heard about raised-bed gardening. Its benefits are many:
- Raised beds are easier to work in — no tilling, little weeding, less bending — and require far fewer tools than in-ground gardening.
- Raised beds warm up more quickly in the spring and stay warm later into the fall, effectively extending your growing season.
- Well-constructed raised-bed frames are attractive, tidy, and make intensive gardening techniques like square-foot gardening easier.
- Properly installed and maintained, the soil in raised beds is light, friable, and easy to work with, providing a superior growing medium for many plants, such as carrots, that suffer in heavy clay soils.
Maintaining an optimal soil blend requires a regular schedule of amendments and care. A disadvantage of raised beds is their tendency to leach out nutrients over time, particularly nitrogen, which is water-soluble and gradually becomes depleted as water runs through the soil. After the fall cleanup and final harvest, gardens can become particularly depleted over the rainy and snowy winter months.
Here in the Pacific Northwest (gardening zone 8), our garden season is finished by around the end of October. By then we have harvested all the summer veggies, pulled out tomato vines and other dying plant material, and have planted our over-wintering garlic and other crops. By early March (early February for those with cold frames), we are starting to plant the spring vegetables: spinach, onions, peas and other cold-tolerant crops.
Prepare your garden now so the soil will be ready for spring plantings.
Prior to doing any planting, though, it’s very important to take stock of the condition of your raised beds and do a little preparatory work. Here are seven useful tips to get you ready for your most successful gardening season ever:
- Check the condition of your existing frames. Are they still structurally sound? Are they mostly level? Are they built of cedar or another safe material? Are they located in an area that gets a minimum of six to eight hours of direct sun a day? If you answered no to any of these questions, now is the time to consider making changes. It is much easier to rebuild, replace, or relocate frames now than in mid-season, and having them properly situated will mean a more productive season for you.
- How good is your existing soil? When you installed the beds, did you use native soil or mix native soil with purchased compost and soil? Are there aggressive or noxious weeds present, such as horsetail weed or blackberries? Having heavy clay soil negates many of the benefits of having a raised bed, and the presence of too many weeds can result a real uphill battle during the growing season. Consider removing the soil in your frames and replacing it if you have either of these issues. Otherwise, just be sure to remove any unwanted plant material before you start amending for the spring.
- Measure the soil level. Is it more than 1 inch below the top of the frames? If so, it should be brought up to give plants in your raised beds as much soil depth as possible.
- Do you have a drip irrigation system? Overhead watering from sprinklers is inconsistent and, over time, will damage wooden frames. Drip irrigation conserves water. Having an automatic timer results in more consistent watering, which results in healthier plants. Perhaps best of all, you don’t have to remember to water, and can go out of town without worrying about your vegetables. Early spring, before your first planting, is the ideal time to install drip irrigation. You may not need to activate it for a few months, but then you won’t have to disturb young plants if it’s already in place.
- Test your soil for nitrogen (N), phosphorus (P), and potassium (K), as well as pH. Existing levels of N-P-K are likely low, if not depleted, by spring. Inexpensive test kits are available at most garden centers to give you an idea of what’s missing. You can then amend accordingly, adding feather meal or blood meal to bump up nitrogen, bone meal to raise phosphorus levels, and greensand or kelp meal to improve levels of potassium. The pH for most vegetables should be around 6.5. If it’s too acidic (common in the Pacific Northwest), limestone can help. Gypsum can help with alkaline soil. Earthworms and compost will improve soil no matter what the issue is (see below).
- Add compost to the soil. We amend all of our clients’ beds each spring with a good inch of mixed organic compost. This feeds the soil, improving its texture as well as adding valuable nutrients for plants. We use a mixture of local dairy manure and worm castings. Although worm castings are relatively expensive (about $11 per cubic foot), adding just one or two cubic feet per 4-foot-by-8-foot bed has yielded significant benefits in the beds we tend. It’s well worth the investment.
- Continue to monitor and amend your soil throughout the season. We have developed our own balanced organic fertilizer blend that we add to garden beds in small amounts every time we plant starts or seeds (most garden centers carry similar balanced organic blends). This mix adds N-P-K as well as other important minerals, like calcium and boron. We augment this with kelp- and seaweed-based foliar feeds on a regular basis. In addition to a good feeding during spring cleanups, our beds benefit from regular doses of organic nutrients, allowing them to be highly productive and to produce maximally nutritious and delicious vegetables, fruit, and herbs throughout the year.