Gardening season is well underway, and you may have questions. To ask one, simply go to the OSU Extension website, type it in and include the county where you live. A photo is very helpful.
Q: Our red flowering currant has been in the ground for at least five years. This year, it looks really sad and terrible. Do you have any ideas as to what is going on? – Lane County
A: We have had some extreme weather events already this year that might be contributing to the state of your flowering currant. Let’s start with the recent hot spell, with 90-degree weather that appeared out of nowhere.
Flowering currant is a Northwest native considered drought tolerant once it is established, but a sudden hot spell right as the canes are leafing out might be more stress than the plant can support. If the roots are healthy but dry, then provide regular, deep irrigation and allow the soil to dry between watering. Prune the canes back to a smaller canopy that the stressed plant can support. At that point watch for new shoots emerging and the plant should be growing back to health.
A more common problem with currant might be related to the particularly wet spring we experienced – many established plants are exhibiting a range of fungal diseases this year. Continuously wet soil encourages the spread of several fungal pathogens that are hard to distinguish but lead to similar symptoms – yellow and wilted leaves being the first indication. If you dig down to check the roots, then look for complete rotting of the fine roots and black lesions on the larger roots.
If you have fungal pathogens in the roots and soil, then treatments are generally ineffective and it’s time to replace the flowering currant with a less susceptible plant.
Since symptoms rarely present themselves clearly, try cutting back the canes and encouraging new growth with some compost and irrigation. Best case, it throws out new shoots and vigorous growth. Worst case, you have until fall to select a new plant for that location. – Stephen Oldfield, OSU Extension Master Gardener
How do I remove grasses from my moss?OSU Extension Service
Q: We have a mossy, rocky backyard. Lately grass has been growing out of the moss. How do we get rid of it? Also, any tips for overall moss health? – Clackamas County
A: Grass that’s invading moss has to be pulled by hand, getting out all of the underground rhizomes that help it spread. Grass needs sun, but moss prefers shade, so if the area you’re trying to grow either in is the wrong sun exposure, one of them will not thrive. Here is an article about mosses. – Kris LaMar, OSU Extension Master Gardener
Q: What are the best grasses or mixtures for a residential lawn that is north facing, shaded with a few hours of direct sun? It will have light traffic on it. – Lane County
A: No lawns are going to do very well with only three hours of sunshine. They will likely become inundated with moss and other weeds because of our long, wet winters and lack of sunlight. You might want to consider planting some shade-tolerant ground covers instead of a lawn.
However, the grasses that can tolerate shade the most are fine fescue, rough bluegrass, and colonial bentgrass. One approach is to blend two or all three of these varieties and see which one does the best on your site. Rough bluegrass does not perform well in the summer if it is not irrigated, but it is the most shade tolerant of the three grasses. Fine fescue and colonial bentgrass will go dormant in the summer if not irrigated but will recover in the fall unless there is a really dry fall that extends the summer. I that case you might lose some grass unless you irrigate some. Colonial bentgrass looks better when it gets mowed lower (1 inch), but in the shade that is not a good idea because it needs more leaf area to capture more light in the shade. However, when you mow bentgrass taller, it will get puffy and not look great. So, if you mow it lower, it thins out from lack of light, but if you mow it taller, it gets puffy.
Fine fescue might be your best choice, but it tends to get more leaf spot fungal disease in the winter when grown in shade. Fine fescue does great in dry shade, but in western Oregon, it can struggle because of all the rain in the winter. You will be able to find a fine fescue mix at a local hardware store. It will be labeled as a “shade” mix. If you want to mix with colonial bentgrass, you will have to purchase it online. The bentgrass seed is so small, you only need to plant 1 or 2 pounds of seed per 1,000 square feet.
Fine fescue should be planted at 5 or 6 pounds per 1,000 square feet. If you want to try Rough bluegrass, you will have to purchase that online as well. You can always try fine fescue and if it doesn’t hold up try interseeding some bentgrass into the stand the following spring or fall. I will just reiterate, in heavy shade, you can have a stand of grass, it just won’t be very dense and it won’t be a show lawn. You have to lower your expectations. Mow it higher (2.5- 3 inches) rather than lower and do not overfertilize it. Apply no more than two fertilizer applications per year (1 pound of nitrogen per 1,000 square feet per application). – OSU Extension turf expert
Will the bottom portion of this trimmed hedge grow back?OSU Extension Service
Q: I trimmed my hedge too much (I didn’t realize that only the outer-most layer has green leaves) and it’s left with lots of “holes” in it for two years. My app says that this is western red cedar. I guess those lower branches don’t grow new leaves anymore because the top branches get more sunlight. What can I do to help the lower branches regrow? – Clackamas County
A: Unfortunately, having done the same thing to our hedge, I can tell you there is nothing that will make them regrow. Planting tall shrubs in front of the damage can help, and it looks like there might be some lower branches of the hedge that could eventually rise up. They will never fill in like you are hoping and will always look “more natural” as they flare out and compensate for the bare area. – Rhonda Frick-Wright, OSU Extension Master Gardener
Alder tree barkOSU Extension Service
A: We planted a red alder in our backyard in 2019. At the time of planting the tree was fairly large, maybe 10-12 feet tall. It has pretty wet roots over the winter as it is adjacent to a swale and over the summer receives no direct irrigation but is a few feet from a lightly watered lawn (it was deep watered the first two summers after planting).
Over the winter and this spring, it showed splitting bark at the root crown and evidence of dead wood underneath and bug holes. The side affected is on the southwest side.
A relative who previously worked with the BLM thought it might have had sun-scalding damage to the bark and subsequent infestation. I was able to collect one of the beetles, which we have seen on the tree and assume are responsible for the holes. Can you provide recommendations for management and thoughts on the survival of the tree? – Clackamas County
A: Yikes, that does look like sunscald. That can be very difficult to manage as it is now wounded. The best to hope for is that the tree will callus over the wounded area. You may have a long scar there for some time, and it is likely decay fungi may get into the wound.
In the long run it may be best to replace the tree, but if you don’t want to do that, I would suggest continuing to help maintain vigor of the tree. Deep watering is a good idea for red alder in this type of situation, but probably only needs it during major drought, like after 1.5 months with no rain. Then only twice per month in August and September.
We don’t recommend covering a wound, as it appears to enhance decay because it keeps the wound moist. – David Shaw, OSU Extension forester
