Q: Nothing is growing in my raised beds since I planted starts in my garden at end the of April. I used these troughs last year with great success. What can I do to boost my sad-looking veggies?
A: Growing vegetables in containers is more challenging than gardening in the ground because a container is a closed system. The only soil the plant has to grow in is the soil you provide, and the plant doesn’t have the option of sending roots deeper or spreading further to supplement its diet. If you used these troughs in the same location last year with great success, then they must get the right light and you likely have watering under control. The slow start this year could be due to soil quality or planting time.
If similar plants were grown in these containers last year, the soil may be depleted in the nutrients the plants need. Whether the bed is in the ground or in a container, it’s good to add compost and apply a slow-release fertilizer about a month before planting time. This gives the soil organisms time to break down the fertilizer into a form that plants can use. After a season or two, you can fertilize at planting time. When planting in containers, you should add fertilizer every two weeks because nutrients are flushed out with watering.
Your plants are already in place, so use a complete fertilizer containing nitrogen, phosphorous and potassium (NPK) with numbers like 10-10-10 on the packaging. Worm casting tea or fish fertilizer will also keep your plants healthy. Yellowing leaves can be a sign that your plants are lacking in nitrogen.
If these vegetable starts were planted out late in April, they may still be suffering some transplant shock, and tomatoes like a soil temperature of 65 degrees if they are to continue growing without interruption. Often the soil doesn’t warm up that much in the Pacific Northwest until late May or even June.
— Stephen Oldfield, Oregon State University master gardener
When wood chips are added to soil they compete with plants for nutrients
Q: We added about 3-4 inches of yard debris compost into our garden. We got it from a landscaping company as a soil amendment. The leaves on our cucumbers, beans, tomatoes and squash are all starting to turn yellow. The cucumbers have it the worst. I don’t know if it’s from the compost or what. I haven’t done a soil test. Any advice? Should I till in some top soil?
A: Yes, the “compost” is the problem. What they called compost has not really broken down yet and still contains large wood chunks. What it is doing right now is trying to break down by using up your soil’s nitrogen — in competition with your plants. Obviously, the “compost” is winning.
According to the Permies website (permies.com), vegetable gardens can suffer when chips are mixed with soil. It states: “These plants don’t have roots (for the most part) that go deep and widely spread; usually their roots are very near the surface and within a 1 meter diameter circle from the main stem. Squash and other vining plants put roots out all along their vine leaf nodes, but these are still shallow roots, so they are vulnerable to nitrogen binding by any wood chip mulch we might put down.”
I think the simplest thing might be to add a fertilizer high in nitrogen. Fertilizers have three numbers on the bag and the first one is nitrogen. Find one that says it is for vegetable gardens and where the first number is highest. Apply it at the rate it says on the bag. That should allow your wood chips to continue breaking down and still give some direct support to your vegetables.
And the good news is, by next year the “compost” really will be compost and you should have good rich soil (although that can depend on water, weather and how much bacterial activity you can encourage in the soil).
Also, it looks like your plants are in raised beds. You will want to make sure they don’t dry out, as the wood chips will not hold the water as well as real soil would. It might be worth spreading topsoil (purchased bagged or in bulk, rather than from the garden) on the top of the beds about an inch deep to help the water absorb. It will also help the wood chips break down.
And next time, check to see what the “compost” looks like before you decide to buy it. Often, those called “3-way” or “4-in-one” are better bets for raised beds. They are a mix of compost, sand, soil and other ammendements.
— Rhonda Frick-Wright, OSU Extension master gardener
Rocks in pots are no help
Q: I have several pots for indoor plants with no drain hole. Does a small layer of rocks help with drainage or should I incorporate the rocks with the potting soil?
A: Rocks actually do nothing to help the plants avoid root diseases or promote healthy plants. Your pots really should have drain holes drilled in them, under which you can add saucers. An Extension article on this topic can be found here (bit.ly/3gaCaP6).
— Kris LaMar, OSU Extension master gardener
Ask an Expert is an online question-and-answer tool from Oregon State University’s Extension Service. To ask a question, visit extension.oregonstate.edu/ask-expert.