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Gardening Column

How cool has it been?

Growing degree days are used to measure accumulated temperatures that support crop growth. Vegetable farmers generally use April 1 as a starting point and a 50 degree F baseline. The high and low temperatures are added together, divided by two and the resulting number has 50 subtracted from it. This is the number of “heat units” for that day and are added up day by day. See attached, in the table, are the cumulative heat units from April 1 through July 4 for St. Helens, Rainier, and Clatskanie.


It has been cool and it is such a shame because cool also is cloudy and many vegetables, especially the sub-tropical ones like tomatoes, peppers, eggplants, corn, cucumbers, and squash and the like are definitely not happy to be losing out on the heat and sunlight of the longest days of the year. That said, the greens have done just fine.

How do you know when to water?

Watering vegetables is a bit of a learned art. Some plants can tolerate temporary moisture deficits and be fine but if onions run short of water while once they have started to bulb, they stop and never get any bigger no matter how much you water. Carrots unevenly watered can fork or split. Blossom end rot on tomatoes is significantly increased by uneven watering.

Raised beds can be tricky. One important reason for raising a bed is so the soil drains better in the spring. This allows for earlier gardening. But that can make summer watering more challenging. The soil mix in the beds generally promotes better drainage and also deeper rooting but sometimes doesn't work in ways that best support vegetable plants. Watering may need to be done more often but less each time.

Your plants will usually tell you but not always. You can buy small moisture meters with 8-10" probes that many people use to check container plants but they do work well in the garden. They don't use batteries and mine has lasted 30+ years. Or you can take a small trowel and dig down about 14-18 inches away from the main stem of your tomato and see what the soil moisture is like. And remember, moles can really affect watering when their tunnels disrupt root to soil contact. So do what you need to do to slow the moles and collapse their tunneling near your vegetables.

Most of you gardeners probably already have a good instinct for when to water. Trust your instincts! While we had quite a bit of rain in May and June, the downpours were spotty. Never count on mid-summer rain giving us much. Water as if we didn't get any! At least July through August! Ultimately as you build compost in your raised beds or regular garden soil, you will have more of a moisture buffer.

Here are a few written pieces that might help: . This is a good OSU gardening publication on a lot of topics with a decent watering section. . This has some information on critical times to water for given crops.

Summer feeding

Most vegetable gardeners start their crops with a balanced fertilizer that is worked into the soil prior to planting. For light-feeding crops, this will be enough to carry them through to maturity

Nitrogen is the plant nutrient that is most often re-applied after the crop is up and growing. There are several reasons for doing this. First, nitrogen is crucial for vigorous plant growth. A lack of nitrogen produces pale green to yellowish plants that often are stunted. Second, nitrogen is readily soluble, unlike other plant nutrients, and can move from the soil surface to the root zone if it is irrigated in.

Gardeners often side dress their crops in mid-summer with a cup of ammonium sulfate (21-0-0) or about half that amount of urea (46-0-0) per ten feet of row. Scatter the fertilizer close to the growing plant and water it in. Some organic fertilizers like blood meal will also work well. It is amazing how fast crops will respond to this treatment. It is not uncommon to see a major change in crop color within two weeks. Corn, onions, the cabbage family, and squashes are particularly responsive. In general, it is not a good idea to apply extra nitrogen to peas and tomatoes.

Pressure Gauge Testing: To July 29. Wednesdays from 9 a.m. to 1 p.m. Free, at the Extension office in St. Helens. Contact for questions and requests for accessibility-related accommodations: by phone and a message option 503 397-3462 or by email at

Pressure canners with a dial gauge need to be tested every year before you use them for accuracy. Canning with a gauge that is off can result in under-processing of home canned foods, which is unsafe. For complete instructions on this opportunity go to: COVID restrictions are still in place at our office which is located at 505 N. Columbia River Highway, St. Helens, Or 97051

The OSU Extension office is closed to face-to-face public contact but you can still reach us!

We are developing plans for re-opening that will have to be approved by the University and ultimately, the Governor. Our target is mid-June. In the meantime, all of us (faculty and staff) will still be working (mostly out of the office), answering phone calls left on our answering machines, email messages (, writing newspaper columns and newsletters, and working to develop programs that can reach you on-line.

We are really committed to helping our communities in any way we can, especially in our areas of subject matter expertise (farming, gardening, forestry, food, food safety, and nutrition, healthy decision-making, and youth education) and any other way we can enrich your life and/or make you safer in these challenging times. Please do not hesitate to contact us! And please, take all steps necessary to ensure that you and your loved ones are safe.

Free newsletter (what a deal!)

The Oregon State University Extension office in Columbia County publishes a monthly newsletter on gardening and farming topics (called County Living) written/edited by yours truly. All you need to do is ask for it and it will be mailed or emailed to you. Call 503 397-3462 to be put on the list. Alternatively, you can find it on the web at

Many Extension publications available online

Are you putting up salsa, saving seeds, or thinking about planting grapes? OSU has a large number of its publications available for free download. Just go to . Click on publications and start exploring.

The Extension Service offers its programs and materials equally to all people.

Contact information for the Extension office

Oregon State University Extension Service – Columbia County

505 N. Columbia River Highway

St. Helens, OR 97051

503 397-3462


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