Why: We have many (hundreds) of rhododendrons as part of landscaping in our development. What is the best time of year to do regular pruning (shaping)? Is there a bad time of year?
In addition, after a few years, the shrubs become too large for their position in landscaping. How often should they be cut back to a smaller size? And how long should we expect the plant to stay in the same spot?
a: best time to prune Rhododendron blooms happen soon after, as the plant’s production of next year’s blooms begins soon after this year’s fades.
While the general rule is not to plant trees or shrubs where they will outgrow their allotted space (height or width), if you need to control their mature size or reduce legibility, the guideline is to cut back only one-third of the stems. Is. Every year, leave at least one or two growth nodes (where other branches or leaves emerge from the stem). This leaves enough leaves to make food (carbohydrates through photosynthesis) for the plant until the following year.
Woody landscape plants are not one to move, especially if planted in the right place initially. Some rhododendrons have been present in Japan for centuries. The species is a difficult one, and reducing its natural lifespan is a human choice, not one required by nature.
, Chris Lamar, OSU Extension Master Gardener
Is that mold in the soil?
Why: I’m weeding under a Japanese maple, and the soil has what looks like white dusty mold or mildew. I searched the internet for what it could be and got conflicting results. Can you tell me what it is and should I be worried?
a: Fear not, it’s a big fungus growing in your bark. It’s the mycorrhizal fungus, which is actually working with your plants. It attaches to the roots and then spreads through the soil in search of nutrients. When nutrients are found, it sends them to the roots of plants and the plants use them to grow. In turn, the roots of the plant produce an exudate that feeds the fungus. A true symbiotic relationship.
, Sherrill Castine, OSU Extension Master Gardener
When is it time to mow the lawn?
Why: What is the best time to desegregate and reseed our lawn? We’re going to take care of it. Does this change the time of year?
a: We generally recommend separating in April when the grass is actively growing and temperatures are usually warm enough at night that any newly germinating grass seed will not be killed.
The only risk with sowing too early is that the germinating seeds may come out with a cold snap. Then you have to re-seed. Check the 10-day forecast for when temperatures stay well past freezing and, ideally, when you’ll have regular rain to help with germination and establishment.
, Brooke Edmonds, OSU Extension horticulturist
What is the best way to transfer blueberries?
Why: We need to move established blueberry bushes and an established red currant bush this month. Should we cut them off first? Is it okay for them to stay in the pot for a few days? Anything special we should know about root care while on the go?
a: Start with root care: Blueberries often have roots right at the surface, with some roots going down, but most leaving around the bush. So dig a wide circle around the bushes (both blueberries and currants), going down at least 12-18 inches. This will give the roots the soil to hold.
Dig your new holes twice as wide and the same depth as you dug. You want the shrubs to be at the exact same soil level as they were before.
Add some peat moss and elemental sulfur to each hole for the blueberries and mix with a trowel. This will lower the pH in the new area. A small bucket of peat and a cup of sulfur should do it.
Add some compost and set the shrub in the hole. Gently cover the soil around the bush. You want air pockets for the roots to breathe, but not large. Water when needed. Add sawdust around the blueberries, starting 5 inches from the base of the bush.
Currant bush needs a lot of compost but not sulfur. They also like soil with good drainage. I would only compost the bottom of the hole and then add compost mulch in the same way as sawdust for blueberries.
Blueberries prefer very acidic soil, about 4.5-5.5. Currants prefer less acidic soil, ranging from about 5.5 to 6.5. We have had very hot summers in the last two years. Plan to water all shrubs on a regular, weekly basis, making sure the soil is moist to about 5 inches. A shady cloth may be necessary if you plant them in full sun. Look for brown spots on leaves in summer; Which may indicate sunburn. If you see this, then spread a shady cloth over the plants.
The less you handle or disturb the roots, the less shock they’ll get, so I don’t recommend keeping them in a pot for any length of time. Delay pruning for a month to ensure that your plants are not in shock from being transplanted. Then I would just prune to take out the dead wood and make sure there is air flow to the center of the plants (once they are out, the center of the bush needs air to stop the growth of the fungus .)
, scheduled caste
What to Plant Where Wild Blackberries Once Grown?
Why: I have a hill above my yard that was overgrown by Himalayan blackberries. I did cut them out but need advice on what to put there instead. It gets full sun.
a: If they were simply cut, they would roar back and some of the plants you added might not be able to compete with them. There are fabrics designed to smooth an area, but even so, the berries will try to avoid the edges. But leaving the field blank would probably lead to serious bank erosion.
Replacement plants will require fairly strong, small woody bushes. Creepers have the best chance. Consider: Arctostaphylos uva-ursi (kinnikinink), Calluna vulgaris (heather), Cenothus thyrsiflorus var. Repens (creeping blue bloom), Euonymus fortunei (Fortune spindle), Euphorbia amygdaloides var. robia (wood spurge), E. amygdaloides ‘Purpurea’ (spurge), Hypericum calycinum (Aaron’s beard), Mahonia repens (creeping barberry), Symphocarpos albus (snowberry), Vinca major (periwinkle).
The suggested planting distance is 3-4 feet. Close to space in poor soil and difficult conditions. In good circumstances, effective cover should be obtained in about two years. In the meantime you will need to mulch with wood chips and weeds as needed.
Another option that may work more quickly is to plant grass—not turfgrass, but creepers such as mondo grass. Or you can plant biomats that are sloped down into the soil and pre-seed with stable plants.
, Pat Patterson, retired OSU Extension horticulturist
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