Summer gardening is in full swing and if you have questions, check out Ask an Expert, an online question-and-answer tool from the Oregon State University Extension Service. OSU Extension faculty and Master Gardeners respond to inquiries within two business days, generally less. To ask a question, simply go to OSU extension website and write a question and the county where you live. Here are some questions asked by other gardeners. What’s yours?
Q: I added sulfur to my hydrangeas in the spring and the flowers came out blue / purple, but now they have faded to a dull white. What happened?
A: Hydrangea flowers only retain their color, be it blue, pink, purple, almost red, etc., for a limited time. Then they fade to a grayish white and later turn gray or brown. Unless you have one that blooms on new wood, you may not see more colorful flowers this season.
For the most common French hydrangeas (Hydrangea macrophylla), the color of the flower indicates the pH of the soil. In strongly acidic soils (pH below 6), the flowers turn blue. In alkaline soils (pH above 7), the flowers turn pink or even red. In slightly acidic or neutral soils (pH 6 to 7), the flowers can be purple or a mixture of blue and pink on a single bush. Note that the selections vary in their pH sensitivity. White hydrangeas remain white regardless of soil pH.
To make your hydrangeas blue, use a soil acidifier and be sure to follow the directions and use the recommended amount for your hydrangea size. You should not exceed the recommendations in the hope of obtaining a deep blue hydrangea. Although this is an organic element, you can easily overstate it.
- Place the soil acidifier in the soil, at a depth of about 4 ″ in a circle halfway between the drip line and the base of the plant.
- Make sure the soil is damp when you apply the acidifier and water it well when you’re done. Water works and makes it effective. If your garden isn’t leaking or doesn’t get constant summer rains, water it with a hose or a watering can.
- Add a 2-3 inch layer of compost around the root ball to add nutrition and help conserve moisture.
This is a slow process when it comes to changing color, don’t expect immediate results. However, the results are long-lasting, but the soil acidifier must be applied in the following years to maintain the blue color. This is not a one-season procedure and your hydrangeas remain blue. It may need to be done three times a year in our temperate valley because hydrangeas have a long flowering time here.
FYI – Having last cut hydrangea flowers here is a technique by Elizabeth Dean of Wilkerson Mill Gardens. Immerse the cut stems in cold water immediately after cutting. Pour about 1 inch of boiling water into a bowl and let it cool for a minute or two. Cut stems to desired length for arrangement. Keep the bottom 1 inch of the stems in the hot water for about 30 seconds. Then transfer the stems to cold water. Voilà!
Healthy roses require at least eight hours of full sun. Stock Photo
Q: I have a rose bush with flowers that are very small, like tea roses, but almost fragrance-free. It was here when we bought our house five years ago. The bush has become more readable each season, even though I have pruned it. The rosebuds are only at the top. Is it too late to severely prune it and still get flowers this season? I pruned it during the winter, but still came back with long legs. How can I get this plant to have more fullness at the bottom? – Washington County
A: If you prune the roses annually, but they are still long in early summer, the problem is probably inadequate sunlight.
Roses really do require full sun; In less than full sun, they are not only long-legged, but develop fewer flowers, smaller flowers, and are much more susceptible to black spot, powdery mildew, and other fungal diseases. If your roses get less than eight hours of sunshine a day (10 to 12 is preferable), seriously consider replanting them in a sunnier spot this fall or winter after they are dormant and after being pruned to a manageable size.
That said, there are several other factors that can contribute to readability, even when roses are in full sun.
- First – variety. Many varieties and cultivars of roses are lush or climbing, rather than shrubs.
- Second: pruning. Each specific variety / cultivar will produce a specific amount of new growth per year. If you don’t trim that growth every year, the new growth adds to the growth of the previous year, and yes, especially in England, you can find entire cabins completely swallowed by roses (which climb frequently). In our area, the general rule of thumb is to cut the rose bushes at waist height on Thanksgiving, and then do the final pruning back to 8 to 14 inches for President’s Day, which tells you how long that rule has been around. general. .
- Third: avoid over fertilizing. It is very common for gardeners to over-fertilize their roses, causing new growth, but not necessarily more flowers. (And aphids go crazy over soft, tender new growth!) If you’re fertilizing more than a little once or twice a year, consider trimming. It will not reduce the number of flowers, but you can see more compact plants and fewer aphids.
The bottom line is that roses need a lot of sun, and no amount of pruning or fertilizer will compensate. – Justin Dune, Master Gardener, OSU Extension
RosemaryOSU Extension Service
Q: I have had this rosemary in a large pot (20 gallons) on the side of my house for a few years. It has grown but not exactly prospered. As you can see, it is quite yellowish and the leaves are slightly mottled. I thought it was a whitefly problem, so I tried for it. The flies seem to be gone, but the problem persists. – Multnomah County
A: Your plant appears to be yellowish, a symptom of a nutrient deficiency, typically nitrogen. Do you fertilize it regularly? Here is an article about your care. Give her a balanced release fertilizer (10-10-10) and she should be encouraged. – Kris Lamar, OSU Extension
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