Welcome a Rhododendron Into Your Garden This Spring

By Brenda Bye, Master Gardener Volunteer

Unknown Rhododendron Species. Photo by Brenda Bye. 

One of the reasons that I love spring in the Willamette Valley is the masses of colorful rhododendrons. It’s hardly surprising that this flowering shrub is so popular, because it comes in a wide range of sizes and colors. Many species are evergreen which is an additional bonus to add structure to your garden in grey winter months. Spring is a great time to plant rhododendrons and it’s not too late. 

There are about thirty species of rhododendron native to North America. They are found naturally in temperate deciduous forests and enjoy the acidic soil found in these wooded hills and mountains. If you are looking to plant a Northwest native, consider Rhododendron Macrophyllum, the Pacific Rhododendron. Its flowers can range from pale pinks to deep purples. It will grow to be 8 to 10 feet in the garden but can grow much bigger in the wild. 

Another interesting native is Rhododendron Occidentale, the Western Azalea. Its flowers range in color from white to pink, but all have a yellow spot on the upper petals that adds interest and beauty. Their flowers are known to be quite fragrant. Unlike the Pacific Rhododendron, the Western Azalea is deciduous and can have very pretty autumn foliage. 

Regardless of which rhododendron you choose, they require similar growing conditions: 

  • Acidic soil with a pH usually between 4.5 and 6
  • Soil that drains well and is rich in organic matter
  • A consistent level of moisture
  • Dappled shade, although it will tolerate a variety of sun exposures
Smaller rhododendron species, possibly Rhododendron Japonica, the Japanese Azalea. Photos by Brenda Bye. 

Having the right soil conditions is very important before you plant your rhododendron. Many of us in Western Oregon already have acidic soils but if you have questions about getting your soil tested or how to interpret a soil test, I would recommend reaching out to your local OSU Extension Office. You can also reach them online at https://extension.oregonstate.edu/ask-expert.

Rhododendrons can be prone to root rot. That is one reason to mix in a good amount of organic matter into your planting site. Some sources recommend a mix of 50% organic matter. In addition to building healthy soil this organic matter will make sure the roots are getting oxygen and not becoming soggy. Organic matter also helps to feed your plant to keep it healthy. 

Smaller rhododendron species, possibly Rhododendron Japonica, the Japanese Azalea. Photos by Brenda Bye. 

Before you place your new rhododendron in the ground make sure to water it well. When you place the root ball in the ground it should be planted at the same level as it was in the pot. Then mulch it with a thick layer of pine bark mulch, which is good for those acid loving plants. Make sure there is a nice ring of space between your trunk and your mulch to prevent fungal diseases. As the mulch breaks down it will also provide more nutrients to your rhododendron. 

Although rhododendrons have specific soil requirements, they are very easy to care for once planted. The mulch and organic soil you used will help the soil have consistent moisture, but they may need additional watering in the heat of summer. They generally don’t need to be trimmed but do benefit from deadheading spent flowers. Rhododendrons appreciate a yearly fertilizer in the fall and a refresh of their mulch. 

Rhododendrons look great as foundation plantings around your home. Their range of colors will fit into any planting scheme and they will bloom for years to come. If you don’t have one yet, consider planting a rhododendron. 

If you are looking for more information about this flowering shrub, check out the resources of the American Rhododendron Society, www.rhododendron.org. And here is a very in depth article from the Pacific Horticultural Society about the Western Azalea https://www.pacifichorticulture.org/articles/western-azalea-beauty-and-fragrance/

Start your garden with these five resources you can access from home

Birdseye view of person and dog at outdoor table in a garden, working on a laptop.
  1. Start with a research-based introduction to growing food at home. Our favorite is Growing Your Own from OSU Extension. Learn when to plant, how to prepare your growing space, stopping pests and more: https://catalog.extension.oregonstate.edu/em9027
  2. Where can you get garden supplies? Plant Something Oregon has a list of suppliers that offer a range of options for safer shopping. Find them here: https://plantsomethingoregon.com/coronavirus/
  3. Where to get your soil tested? Master Gardener volunteers are not currently able to test soil pH, so gardeners will need to send samples to soil testing labs found in Analytical Laboratories Serving Oregon: https://catalog.extension.oregonstate.edu/em8677

These labs can provide a variety of services. Most home gardeners who are growing plants in the ground will want to check soil pH as well as levels of nitrogen, potassium and phosphorus. Many labs offer the option to request recommendations for amending soil when ordering their tests. Learn how to take a good soil sample to achieve the most accurate results with A Guide to Collecting Soil Samples for Farms and Gardens: https://catalog.extension.oregonstate.edu/ec628

4. Use research-based resources to find garden solutions. OSU Extension offers straightforward tested resources to build resiliency for by growing gardens in this amazing virtual collection: https://extension.oregonstate.edu/gardening

5. Connect with real gardeners to get help! Though our offices may be closed, OSU Extension Master Gardeners are still available to answer your gardening questions by phone or email. Please leave us a detailed voicemail and a callback number. We’re also checking email! Share your photos of plant or insect problems with us. Master Gardeners will research your question and give you a call back or send an email. In Benton County: (541) 713-5000 or email: bentonmg@oregonstate.edu In Linn County: (541) 967-3871 or email: linn.mg@oregonstate.edu

Before Reaching for Pesticides, Get to Know Beneficials – The Good Guys!

By Judi Di Bord, Master Gardener Volunteer

Did you know there is an alternative to controlling pests in your garden by using a pesticide?  Attracting beneficial insects, like lady beetles, green lacewings, praying mantis and dragonflies can help control insects that feed on your plants.  Beneficials don’t just help control pests. Some beneficials are also important pollinators! 

Ladybug (Coccinella septempunctata) on an Common Yarrow's umbel (Achillea millefolium)
Ladybug (Coccinella septempunctata) on an Common Yarrow’s umbel (Achillea millefolium). By Hélène Rival on Wikimedia Commons.

How can you attract beneficials to your garden?  One way is to purchase them at a local garden center and release them into your garden.  You can also attract them to your garden by growing plants to provide an enticing habitat for them.  If you are able to dedicate some space to growing these habitat plants, the rest of your garden can reap the rewards.

Following are some recommendations from the Penn State Extension Service:

  • Carrot Family (Apiaceae)  Plants in the carrot family are especially attractive to small parasitic wasps and flies. Interplant them in your vegetable garden and flower beds. Plants in this family include: caraway (Carum carvi); coriander/cilantro (Coriandrum sativum); dill (Anethum graveolens); fennel (Foeniculum vulgare); Bishop’s flower (Ammi majus); Queen Anne’s Lace (Daucus carota); and toothpick ammi (Ammi visnaga).
  • Aster Family (Asteraceae)  Attractive to larger predators such as lady beetles and soldier beetles. Incorporate into the vegetable garden and flower beds. Plants in this family include: blanketflower (Gaillardia spp.); coneflower (Echinacea spp.); coreopsis (Coreopsis spp.); cosmos (Cosmos spp.); golden marguerite (Anthemis tinctoria); goldenrod (Solidago spp.); signet marigold (Tagetes tenuifolia); sunflower (Helianthus spp.); tansy (Tanacetum vulgare); and yarrow (Achillea spp.).
  • Legumes (Fabaceae)  Generally grown as cover crops and attractive to many beneficials. Plants in this family include: alfalfa (Medicago sativa); fava bean (Vicia fava); hairy vetch (Vicia villosa); and sweet clover (Melilotus spp.).
  • Mustard Family (Brassicaceae)  Attractive to beneficials that are parasites and predators of the insect pests of the mustard family (broccoli, Brussels sprouts, cabbage, cauliflower, kohlrabi, mustard greens). Be sure to plant these away from the garden rather than in the garden since these plants attract pests as well as beneficials. Some are common weeds, such as yellow rocket and wild mustard. Plants in this family include: basket-of-gold alyssum (Aurinia saxatilis); mustards (Brassica spp.); sweet alyssum (Lobularia maritima); yellow rocket (Barbarea vulgaris); and wild mustard (Brassica kaber).
  • Verbena Family (Verbenaceae)  Attractive to a variety of beneficial insects. Many plants in this family are favorite garden flowers. They include: lantana (Lantana camera); Buenos Aires verbena (Verbena bonariensis); hybrid verbena (Verbena x hybrida); and lilac vervain (Verbena rigida).

Beneficial insects also need a source of water. Shallow containers such as ceramic pot saucers with pebbles for the beneficials to rest on are best.

Suggested OSU Extension publications:

PNW550: Encouraging Beneficials in Your Garden

For kids:

EC1601: The Wildlife Garden: Dragonfly

EC1604: The Wildlife Garden: Lady Beetle

EC1605: The Wildlife Garden: Praying Mantis

Suggested websites:

National Pesticide Information Center, Beneficial Insects.

Penn State Extension, Attracting Beneficial Insects

Sick plants? Get the most out of Master Gardener Plant Clinic!

By Elizabeth Records, Master Gardener Program Assistant

Previously published in Growing.
 

Three gardeners standing at info booth.
Master Gardeners are here to help at Pop up Plant Clinics in a location near you.

It’s gardening season! Whether you’re a longtime gardener or are new to growing things, OSU Extension Master Gardener Volunteers are here to help you grow your best garden yet and deal with garden challenges.

Master Gardeners are volunteers who complete a specialized training program and work as a team to help find solutions to garden problems for people in our community. We are from all walks of life and have widely varied gardening interests and experiences. Together we bring lifetimes of collective garden knowledge to solving plant problems with research-based information. Here are some scenarios where Master Gardener volunteers can help:

Plant Identification

You are digging in the garden and find an unfamiliar plant that you did not put there. Will it produce lovely flowers or tasty food? Or will it prove to be an invasive weed that takes over your garden? Master Gardener volunteers can help you find out. Bring a sample of your plant including a full branch or stem with any leaves, flowers and fruits that may be present.

Insect issues

You find a mystery insect in the garden and wonder if it is going to harm your plants or be a helpful pollinator or a useful predator of insect pests. A dozen insects appear in your garage, and you don’t know if they are a simple nuisance or are likely to feed on you, your pets or your home. Master Gardeners can help identify insects and suggest how to manage them! Bring the insect in a sealed jar, or a high resolution photo of the insect on a pale colored background, next to a ruler or coin so we can tell the size.

Gardening guidance

Just starting your first veggie garden and wondering when to plant, or what varieties do well in your location? Want to make your garden more sustainable by using less water, attracting more pollinators or using fewer chemicals? Short on space but excited to grow fresh herbs or salads on your windowsill? Whatever your gardening goals, Master Gardeners can help you find research-based information to get the most from your garden.

Diagnosis and recommendations          

Your previously healthy plant suddenly wilts. Brown spots appear in your grass. A tree that produced lots of fruit in the past stops setting fruit. Master Gardener volunteers can help figure out what is going on and decide what to do next for best results. Bring samples and/or photos that show the problem and also the surrounding area.

Get the most out of plant clinic
  • Be ready to answer questions that will help Master Gardeners hone in on the source of your problem so we can provide the best advice possible. Master Gardeners might ask, “how long has this problem been going on?” and “Are all of the similar plants affected, or just one?” “What treatments have already been attempted to remedy this situation?”
  • Bring good samples – you can always call us for suggestions to bring the most helpful samples.
  • Master Gardeners cannot answer questions about State or Federally controlled plants, identify mushrooms, or offer medical advice. We are pleased to assist with all your other garden questions to the best of our ability.
  • Sometimes we may need input from other team members or horticulture faculty to resolve your question. Be ready to share an email or phone number if we need to do some extra research and follow up.
  • Have fun and enjoy your garden, even when things don’t go as you expected!
Plant Clinics near you!

Find us at your local office most weekdays from 9-12 and 1-4. Email or leave a phone message anytime.

Benton County

  • 4077 SW Research Way, Corvallis, OR97333
  • Call with your question: (541) 766-6750
  • Email your question and any photos to: bentonmg@oregonstate.edu

Linn County

Do you have fruit trees? Tips on codling moth management from MG Alan Taylor

Alan Taylor has been a Benton County OSU Extension Master Gardener since 2015. When he’s not growing grapes and fruit, Alan puts his scientific background to use at the Master Gardener plant clinic by helping communities, teaching new volunteers and troubleshooting equipment.

If you have ever bitten into an apple and gotten a taste of a worm, there is a good chance it was the larva of a codling moth, a major pest of apples in the Pacific Northwest. Read on to see how Alan uses the data to get ahead of codling moths– and how you can, too!

biofix (plural biofixes)
(biology, pest management) A biological event or indicator of a developmental event, usually in the life of an insect pest, that initiates the beginning of growing-degree-day calculations.

Codling moth larva exiting fruit to pupate (Washington State University – E. Beers, July 2007)

For codling moth, this is the first date of consistent capture of adult moths in pheromone traps, and this year the consensus date for the mid-Valley biofix appears to be 29 April.

Now the fun part: CLICK HERE to visit the IPPC codling moth model (Brunner and Hoyt).

This link to the degree-day model gives a map to let the user select the weather station, and the correct biological model has already been selected. The user will need to enter the biofix date (I’ve been using 29 April) and then the calculations will give the appropriate dates for spraying.

For example, I clocked on a weather station in SW Corvallis, then entered 4/29 as starting date. This gives 20% hatch at 6 June and 50% hatch at 18 June. These two dates are the timing of the two sprays of insecticide for the first generation of codling moth.

Then I selected a site NW of Corvallis with an elevation of 780’, more representative of where I live (unfortunately no good sites both to the SW and at elevation are shown in the map), and the prediction is 20% hatch on 11 June and 50% hatch on 23 June. You can see the effect of a cooler location or microclimate. I have consistently noted that bloom and ripening of my fruit (apples, pears, grapes, etc.) is 7 – 10 later than that of friends down in Corvallis. Being at ~700’ and somewhat closer to the coast does make a difference, and I’ll be allowing for that in my sprays this year. Realistically, this is a conservative estimate, because I should also have a later biofix at my site, but I’ve chosen to ignore this. Last year, I used the timing for the Valley sites, and my apples were very clean.

Just to complicate things, not all insecticides remain effective for 12 days. I think spinosad, which I used, is supposed to be good for 10 days. Always compromises, so I used the model timing of the first spray, then waited 10 days for the second spray.

Finally, there are 2 and sometimes 3 generations of codling moth in the Valley. I’ll use the model to predict the spray timing for the second generation (we can cover that later), and I chose to ignore the potential 3rd generation last year. Four sprays is enough!

Read more about codling moths and how to manage them in the Pacific Northwest Insect Management Handbook.

“Project Happy Apples: Reducing codling moth damage in backyard orchards” is a free webinar for Master gardeners and home orchardists alike. Watch it HERE.