Gardening Column

Hazardous waste collection event August 29

Due to COVID-19, three earlier Household Hazardous Waste Collections were canceled. The county will offer a collection event on from 8 a.m. to 2 p.m. August 29 at the Transfer Station in St. Helens. These are important events if you have accumulated household quantities of hazardous materials that need a proper (and free) disposal. Please check the Columbia County website for further information on what they take and updates in case of COVID cancellation:

Pressure gauge testing

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

Prune spent roses

This is the month to tend roses. How you prune depends on the type of rose. If your roses are continual bloomers – hybrid teas, floribundas, grandifloras, miniature roses, English roses and landscape roses – prune off any spent blooms now. You’ll be encouraging the plant to create more buds.

General pruning wisdom tells us to prune “back to a 5-leaf” cluster, the spot on the stem where a 5-leaf set emerges. However, English research indicates that a 3-leaf set is just as good and may, in fact, leave more leaf area for photosynthesis and is better for the plant. The plant will produce new floral buds that take about six weeks to bloom.

Remove fallen leaves and prunings to discourage disease. Remember to keep watering your roses. They need much more water in the summer than many people realize.

Miscellaneous topics

Gardeners need to understand that compost is not a nitrogen-rich fertilizer. This is especially important for annual crops like vegetables. These crops require a lot of quickly available nitrogen. When compost is made, either at home or by a commercial facility, most of the nitrogen is lost in the composting process. In fact, if the material is not completely composted, applying it to the soil without

a supplementary source of nitrogen can actually result in a nitrogen tie-up of what you already had there.

The soil microorganisms gobble up your nitrogen to complete the composting process. This is not to say compost is bad to add. It has a positive impact on soil structure and will, after repeated applications, be able to “bank” some N and other important minerals for your plants. It also improves the biological life of the soil which is important for disease and insect suppression. But you will need to add N in relatively available forms to perk up your vegetables and annual flowers. I have had a lot of questions about plants failing to thrive and looking yellow green. That is an N deficiency 95% of the time and possible, even at this late date, to fix on crops still growing. Call me if you have questions.

Irrigation is so important in August. Subsurface moisture is depleted by now, temperatures are hot, and plants are at crucial stages of growth. We get very little rain in August. Most gardens and lawns will need an inch of water or more per week to keep going. Trees or shrubs planted this spring need more water because their root systems are not well developed.

Sunburn has been a problem on apples and broadleaf evergreens. The 95º weather was too much to handle. Most of the damage is on the south or west side of a plant. Damaged apples will not mature normally and will often fall off before ripening. Damaged leaves are browned at the tips or margins. They look bad but generally don’t constitute more than a cosmetic concern. If all the leaves were affected, the plant was grievously short of water or something is wrong with the roots.

Blossom end rot of tomatoes (a calcium shortage and not a disease despite its name) can be reduced by adequate and even watering. Lime your garden area this fall with 10 pounds of agricultural lime per 100 square feet. This will be good for three years.

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

We are developing plans for reopening 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 online.

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

The Oregon State University Extension office in Columbia County publishes a monthly newsletter on gardening and farming topics (called County Living) writ-ten/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 click on newsletters.

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 OSU 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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