It has been a mild and spring-like March and that means it is time to start gardening. If you have any questions, check out Ask an Expert, an online question-and-answer tool from Oregon State University’s Extension Service. OSU Extension Faculty and Master Gardeners answer questions within two business days, usually less. To ask a question, just go to it OSU Extension website and type one in and state the county where you live. Here are some questions from other gardeners. What’s yours?
Q: We have two raised garden beds in our backyard, and I was looking for advice on how best to prepare the ground for this year’s garden. Both garden boxes are approximately 8 feet by 2 feet long by 2 feet wide and 2.5 feet deep. One was built two summers ago and the other was built last summer. Both beds were filled with compost when they were built.
Last year we added a little bit of compost to the original garden box and mixed it with the soil that was already there. Furthermore, we have not added anything else to the bottom. Is there anything we need to add to these garden boxes to replace the nutrients that the plants have used up over the years before being planted in them this year?
We grew potatoes, bell pepper, basil, carrots and garlic in one garden box. The newer of the two had tomato plants, green onions, and carrots, although the tomato plants took over so the other vegetables didn’t survive. – Marion County
A: Vegetables usually do well in a new bed for a year or so, but because they are annuals, they quickly deplete the nutrients, which need to be replenished regularly.
Compost is an excellent addition to condition your soil and improve it over time. However, decomposition is a slow process, so compost is not considered one fertilizer. Many necessary nutrients for plants are minerals such as those found in rock. Nitrogen is quickly used by plants and leached from the ground by rain; therefore most fertilizers contain a combination of nitrogen (N), phosphorus (P) and potassium (K).
This is not to say that vegetables need Lake nitrogen (in fact, too much can result in lush foliage and little fruit); but the nitrogen needs to be replenished more often. You will usually see for the three numbers on the fertilizer packaging primary ingredients in the order listed above, but many also contain fertilizers subordinate and micro nutrients that are also needed by plants in small quantities.
In a raised bed, it is difficult to adjust the nutrients and soil pH for different vegetables. Your best approach is to aim for a slightly acidic soil (6.0-6.5 pH). Rotate your vegetables every year so that the vegetables in the same family are not grown in the exact same place, which will also help reduce the build-up of pathogens that can cause disease. Families include Solanaceae (tomatoes, peppers, potatoes, and aubergines), the allium group (onion, leeks, garlic), and the leafy greens.
Ideally, you should have a soil test to determine what your soil is now, and adjust or fertilize it accordingly. Many people do not want to test for a small garden, but understand that it is a bit like working in the dark without a test.
Good soil is about 3% -5% organic materials at various stages of decomposition. This ensures good soil health, soil cover and the maintenance of healthy micro-organisms in the soil. In addition, you also need fertilizers that can be either organic or non-organic (ie conventional or synthetic). Look for a high-quality balanced fertilizer with proportionally higher phosphorus and potassium than nitrogen, such as 10-20-20.
Refer to this OSU publication for more information.
This publication also provides an excellent guide to vegetable gardening in general.
One last point I would like to make is that tomatoes are often better planted in a very large pot, where they won’t crowd out other vegetables. You can also stake them out and prune them so they grow up, not out. Read more in this publication. Lynn Marie Sullivan, OSU Extension Master Gardener
Question: I want to practice gardening without plowing and combine that with green manures / green manures to improve my soil structure. However, I don’t know how to start. My garden has issues with massive amounts of weed seeds, clay soil, compaction where I’ve walked and an area where we fight invasive brambles and thistles. How can I implement plow gardening with all these problem areas? – Marion County
A: You may want to tackle the obvious problem areas first to get the garden going, then apply the no-work / green manure techniques once you get started. Moist, unprotected clay soil is very prone to compaction, so I would outline the garden space and decide which areas would be special pathways and what the growing space would be.
The existing compaction in the grow rooms is a short-term problem, so you may want to consider digging in organic matter if the soil is dry enough to break it up with a minimally invasive tool such as a digging fork. You can maintain the structure of the soil afterwards with the help of mulch or green manures.
I wouldn’t let the cannabis seeds discourage you. Remove any perennial weeds and any annuals as they sprout and you will gradually reduce the seed bank and the number of weeds you have to deal with. The blackberries are an invasive weed so you’ll want to get rid of those too, but they may have had the advantage of protecting or even improving the soil structure under the canopy and suppressing other weeds.
Removal of these, including root systems, can reveal a soil already ready for no-plow gardening, with the caveat that there are bound to be blackberry seeds that will sprout and need to constantly get rid of weeds. You do not specify which thistle is, hopefully it is an annual species and not the Canadian thistle, which is perennial and very difficult to eradicate. Feel free to write back and explain this.
This short article provides some additional suggestions:
This extension publication offers many additional guidelines, but not specifically on no-plow gardening. As I said, feel free to write with any questions. – Neil Bell, OSU Extension horticulturist
Red Clover in Washington County. Oregonian file photo.
Q: We have been growing red clover this winter as a ground cover. We turned it around last Saturday. My Master Gardener material tells me to wait three weeks to plant. How critical is this period? What are the disadvantages of planting earlier? Does it matter if we put in or start seeds? – Multnomah County
A: In this Washington State University Extension publication, below the section on ending a ground cover, it says, “Freshly terminated ground cover residues can inhibit seed germination, including the germination of desired vegetable seed. Waiting three to four weeks to plant vegetable crops after finishing ground covers often improves their establishment. “
The OSU Extension publication “Growing Your Own” provides planting timelines. The soil is too cold and wet to plant this early, so perhaps waiting won’t hurt your gardening plans. – Jacki Dougan, OSU Extension Master Gardener