Rhododendrons Direct and More!

In late February of 2022, some rhododendrons that had just arrived from another nursery tested positive for Phytopheria ramorum.  When we receive plants from other partner nurseries, we isolate the plants from the inventory of the rest of the nursery until we can determine the health of the plants.  In this case, the delivery of rhododendrons was destroyed.  Included in the destruction were any other rhododendrons that were in the isolation zone.  No plants were shipped to customers from this group.

Phytopheria ramorum(P. ramorum) is a fungus like pathogen also known as Sudden Oak Death. There are over 100 know hosts to P. ramorum, with rhododendrons being one of them. Because this is such a devastating disease to certain species of oaks, when P. ramorum is detected in a nursery, the USDA is notified and certain protocol is put in place. 

Unfortunately, this protocol included alerting customers that had purchased plants from the nursery six months prior and through the month of May.  USDA alerted local agricultural agencies with a form letter, and then the local agencies determined how they would interact locally.  The unfortunate part was that many customers were notified about plants with the disease, however it was not explained that the plants they had received never came in contact with the diseased plants.

At Rhododendrons Direct, random sampling of thousands of plants take place every year.  Besides the newly arrived plants from another nursery, we have not had any plants test positive for P. Ramorum.  Please feel free to write if you have any questions or contact your local agriculture department. 

Proper planting of your rhododendron is the first step in the care for your plant.  After receiving your plant, it is best to get it into the ground as soon as possible.  If for some reason, planting needs to be delayed for a couple of days, it is best that the plants are removed from the shipping box.  Plants can go through many temperature zones during transportation that can impact their appearance on arrival.  Drooping leaves and a dry root ball is common on arrival and your plant will revive.  Getting water to the root ball and air circulating around the plant as soon as possible is important.  If you plant is not going into the ground right away, remove the zip tie from around the stem of the plant and poke several holes in the bottom of the plastic bag holding the root ball.  Add water to the bag filling up the bag and allow the bag to drain through the holes.  Your plant wants to have a moist root ball, but not wet.  Place the plant in a spare plant container or prop it upright so that the root ball can drain and air can circulate around the plant.  Leave it in a shady, cool, protected spot outside.  Check the root ball daily to make sure that it remains moist.  Do not bring your plants into the house while they are waiting to be planted, the humidity in our houses is usually too low for the rhododendrons. Your plant should perk up in 48 hours.

Rhododendrons are shallow rooted plants and will live in the top 18” of soil.  To prepare the area for the plant, dig a hole as wide as the top of the plant and about 6” deeper than the root ball.  We recommend only adding organic material to your soil initially so that the plant does not go into shock. We recommend using fine fir back or pine bark mixed with the existing soil at a 50/50 ratio if the soil is compacted.  If your soil drains poorly (water does not drain out of a hole you have filled with water in 60 minutes), consider planting your rhododendron on a mound.  There is no need to prepare a root ball other than to make sure it is going into the ground moist.  Plant the rhododendron so that the top of the root ball is even with the surface of the soil.  Once planted, you should see a single stem emerging from the soil and an outline of the root ball even with the surface. 

It is important to water your plants regularly while they are establishing a root system.  Using the same irrigation system that is used on established plant may not be enough water for your new plant.  Check the soil around your new plant by putting your finger into the soil and making sure that it is moist, not dry or wet.  As you plant establishes, it is OK to use a slow release fertilizer that comes in pellets on the surface of the soil. 

Every landscape if different and every yard has a different climate zone.  The continued care of your plant will not be a “one size fits all” instruction.  There are fantastic books published on the care of Rhododendrons and The American Rhododendron Society (https://www.rhododendron.org/planting.htm   and https://www.rhododendron.org/) is a great resource for planting and care information.  They also list contact information for local chapter that are great resources for your area. 

Once your plant is delivered, we can no longer provide care of the plant and the survival of the plant is up to you.  Please find below the top ten suggestions for plant survival.  This is simply a guide for the best care of your plant.  We cannot give you a one size fits all guide, because a plant growing in Washington State and a plant growing in North Carolina will have different environments and will need different care.  The American Rhododendron Society (www.rhododendron.org) lists more tips as well as a directory of local chapters that have local members that are usually willing to help answer local questions. 

1 – Rhododendrons need well-draining soil.  Rhododendrons need to have their roots moist but not wet.  To determine if your soil is well draining, dig a hole that is 12 inches deep where you will plant your rhododendron.  Fill this hole to the top with water.  If the water remains in the hole for more than an hour, your soil does not drain well.  In this case, consider planting your rhododendron on a mound.  Refer to planting tips at https://www.rhododendron.org/planting.htm.

2 – Plant your rhododendron at the correct height.  The root ball of your plant needs to be at the top of the soil level.  A properly planted rhododendron will have a single stem emerging from the soil and visible outlines of the of the root ball right at soil level.

3 – Make sure your plant is getting plenty of water.  Newly planted shrubs will not have the same root resources for several years as the established plants in your yard.  Please do not assume that your current irrigation system that is tending to your established plants will be enough for your new plants.  Running water directly to the root ball of your new plants will help get the water needed.  Establishing rhododendrons need to have moist, but not wet roots.  The best way to test if your plant is getting enough water is by sticking your finger into the soil near the roots and seeing if the soil is moist. 

4 – Generally speaking, rhododendrons do not like the heat and/or too much sun.  Rhododendrons also cannot tolerate too much shade.  When you are determining where you will be planting your rhododendron, pick a spot that will receive 3 to 8 hours of direct or filtered sunlight.  In general, rhododendrons with smaller leaves tolerate the sun more than the larger leaf varieties.  Yellow and Orange blooming rhododendrons tend not to be as sun tolerant as some of the darker blooming rhododendrons and will do better in 2 to 6 hours of direct or filtered sun.   When selecting a plant site, take into account landscaping material or surrounding structures that will hold heat(such as concrete, landscape stone, brick foundation).  This heat need to be taking into account for additional exposure to heat.

5 – We all want our plants to have the best start as they are planted.  However too many soil additives at the time of planting can shock or stun the plant.  Unless you have had your soil tested, do not add any acid boosters to the soil at the time of planting.  If your soil is low acid, add the boosters to the soil and have the soil retested before planting.  Plant into existing soil or soil with natural composts added.  Adding a slow release fertilizer as a top dressing is OK.  The goal is to not shock the plants as they are growing in their new environment.

6 – Root ball manipulation is not needed when planting new plants.  We have transplanted over a million rhododendrons and have found in all cases, scoring or disturbing of the root ball does not benefit the plant.  If you plant during the growing season, when the plant is out of dormancy, new moist soil pressing on the edges of the root ball will stimulate fine root growth in just a few weeks. 

7 – Rhododendrons will need a regular supply of water.  Planting rhododendrons under a canopy of trees makes for a beautiful landscape, however the rhododendron will compete with the water resource of the tree roots.  When planting under trees or in densely planted areas, consider planting your rhododendron on a mound over the root population.  This will allow your rhododendron roots to establish above the tree roots.  Weeds also compete for water.  Keeping the planting areas clear of weeds will allow your rhododendrons to establish wider roots faster. 

8 – Purchasing the proper plant for the proper climate zone.  Not all rhododendrons are hardy to the same cold temperatures.  We give specific hardiness temperatures for the plants.  If a plant is rated Hardy to -10F, it will probably not thrive in an area where the temperatures get below -10F. There are some enthusiasts that push the boundaries on temperatures, but for the average landscaper, making sure the plants you purchase are hardy for your area is very important.

9 – Proper soil conditions are important to have your rhododendrons thrive.  Visually, we cannot always tell what is going on with the soil just by site.  Local extension offices may be able to do a limited amount of soil testing for you that can help.  There are a couple of situations that would warrant not planting rhododendrons unless you have your soil tested specifically for these conditions.  Rhododendrons want acidic soil.  Many new construction site where new concrete is poured or there is construction waste (such as plaster or drywall) in the soil will make the soil be very basic (opposite of acidic).  Bringing in new soil is highly recommended for newly constructed planting beds.  If you have poor draining soil with sitting water, or have had a rhododendron or other woody shrub instantly die, there may be fungus in the soil.  Soil fungus is very difficult to control because it spreads by water.  Our recommendation is to select a fungus tolerant shrub rather than a rhododendron for this area. 

10 – Container planting can be done with rhododendrons, however, it will take special care.  There is an article about container growing on our website.  In a sentence, your rhododendrons in containers will need more water and regular slow release fertilizer than a rhododendron planted in the ground. 

There are hundreds of books written about the care of rhododendrons, and to try to sum it all up in ten areas is simply not possible.  With the magic of the internet, there are so many resources out there to reference.  Again, the best place to start is with the American Rhododendron Society and work out from there. 

I wanted to share with you two sections of the web site that are generated by the dedicated rhododendron community of the American Rhododendron Society.  First of all, The American Rhododendron Society(ARS) is group of dedicated plants owners formed into regional chapters throughout the country.  The people that make up the chapters are the true “boots on the ground” people who love and grow rhododendrons.  They have years of experience with planting and growing rhododendrons in their distinct regions.  The members of these chapters are a valuable resource for growing rhododendrons in their region.  There are two sections of the web site that were created based on their recommendations.
Suggested Rhododendrons by Region of the United States is a section that links what the members of specific regions consider good performers.  These are plants that the members of the local chapters have found to do well in their area year after year.  These are not the only plants that will grow in these regions, but are the plants that come highly recommended by the members. It is worth the time to browse these and neighboring sections to see if there are any that catch your eye.
The section Award Winning Rhododendrons is a list of rhododendrons that have received the Title of Rhododendron of the year by one or more of the growing regions of the ARS.  If your region has awarded a plant Rhododendron of the Year, it will have excellent foliage and flowers, have an attractive plant habit, be pest and disease resistant and be cold hardy for the region.
The American Rhododendron Society is an excellent resource for everything Rhododendron.  The members of the local chapters are some of the best people you can know.  If you have any knowledge to share or would enjoy spending time with plant loving people, I would encourage you to contact your local chapter and attend a meeting when the time is right! 

Rhododendrons can be grown in containers with success.  Having your plants in containers can give you many options for your landscaping.  It allows you to give “feet” to you plants to find the perfect location or to give them additional shelter during the winter months.  Container growing is also a great option when ground is not available such as on a deck or balcony. 
When you are growing a rhododendron, or any other plant in a container, it is very important to consider the resources that your plant will need during its life.  The larger the plant will grow, the more nutrition and water it will need to prosper.  When considering rhododendrons for containers, selecting plants that will not grow as large will allow you to plant into a container that you can move around without needing a forklift and also allow the plant to reach it’s potential.  Selecting a rhododendron that will grow to four feet tall and wide will allow the use of a fifteen-gallon container that is still mobile.  For each foot less in height, you can subtract five gallons in container size.  These sizes are approximate recommendations.
The soil medium that you choose is very important.  Rhododendrons need to have well drained soil.  A potting mix with sand works great.  Do not use the soil blends that hold moisture.  Make sure that the top of the root ball is at the soil level.  Spreading mulch or fine bark at the top of the container will give your plant a layer of insulation to help with water evaporation.
When you plant your rhododendron in a container rather than the ground, it will miss all the resources that the ground provides.  You will need to water your plant more often.  Leaving a saucer under the container is not recommended.  Remember, your plant wants to have moist roots, not wet roots.  You will also need to feed your plant on a regular basis.  Use a slow release fertilizer designed for rhododendrons.  We do sell a very good fertilizer on our web site, but you can also find it at your local nursery or big box store.  You will need to apply this fertilizer at least twice a year, following the directions on the package.
When your rhododendrons are in the ground, the earth acts as an insulator for the root system.  In a container, these roots are exposed to the large fluctuations of the daily temperatures.  Keep this in mind when placing your plants in direct sunlight.  You will want to avoid the container from getting too hot.  Also, in the winter, roots are exposed to the cold air temperatures.  If you get subzero temperatures, consider moving your plants out of areas of exposure.  A great place is by the house.  Rhododendrons do not like the temperatures and humidity of the house, so keeping them outside is the best idea. 
Container growing is a great way to add color to any place outside!

We are a nursery that grows only rhododendrons.  We are different than your retail nursery down the street or the big box store in that we grow the product that we sell.  When you go to a retail nursery, all the plants on display were grown for that season only.  Our plants are grown and for sale from the second year onto almost fully grown plants.  Because we take care of this plant over what could be ten years or more, we have to transplant them into larger pots as they grow.  Rhododendrons tend to get a container shift from us about once every three years.  So at any given time, about 1/3 of our plants look like the plants you would see at a retail nursery where the top of the plant matches the container they are planted in.  Because we do not progressively move our pot size up every year, we sell our plants by width of the foliage and then give you the typical container size that you would find at a retail nursery of that size.  For example, a plant that we sell as an 8” to 12” plant would typically be sold at a retail nursery in a two-gallon container.  Our 8” to 12” wide plant could be in either a one, two or three-gallon size nursery container at our nursery. 

Please send us a message if you have any questions about sizing.  You may also what to look at understanding nursery container sizes.  A one-gallon nursery container does not even come close to holding one fluid gallon.  Learn More Here.

It is a privilege to be able to work with so many of my customers when they are having issues with their rhododendrons.  I wish I could just stop by your yard and have a conversation, but for most of the time we are limited to emails when there are sometimes hours or days that go by between the time we get to converse.  I wanted to share with you an article that was published by the American Rhododendron Society in 1994 by Jan D. Kelley.  I have shared this with many customers already and I hope that this article can help in two different ways.

This article my help preventing some of the issues that can occur later.  I enclose planting instructions with every plant we sell, but it does not cover the care of the plant.  Here are some Very, Very basic steps as to what to avoid. 

If your plant is struggling, you might find something in this article that may aid you in changing the environment for your plant.  I agree with the author that the great majority of rhododendrons that I see struggle have been planted in an environment that does not allow the soil to drain away excess water.  I hope that article may help in a few questions you may have.  I am always available via email for all questions!  Jim

https://www.rhododendron.org/v48n2p85.htm

 Top Causes of Death in Rhododendrons

Jan D. Kelley
Drain, Oregon

Our hopes soar with the coming of spring as we anticipate another excellent growing season for our rhododendrons with their exquisite flowers.  As we ponder the fantastic new hybrids in the pages of the several catalogs that we receive our vision of being successful gardeners bursts forth.  However, as you reflect upon last year’s plant losses a ray of doubt creeps into your consciousness, and the nagging question emerges: “Why did that plant die?”

For the past 15 years I have enjoyed raising rhododendrons.  During that period of time I believe that I have killed rhododendrons in every conceivable way.  In the remainder of this brief article I would like to identify some of the various ways that rhododendrons succumb in our yards and gardens.  My experience indicates that most rhododendrons die from about seven causes.

To begin with, excessive water kills about 75 percent of all rhododendrons purchased.  Rhododendrons are fibrous, shallow rooted plants that need good drainage to perform well.  Historically, gardeners have been told to dig a hole twice as wide and twice as deep as the root ball.  After the hole is completed put the plant in the hole and back-fill it with a mixture of peat, soil and other amendments. Many rhododendrons die from this guidance.  The result of digging the hole and planting the rhododendron in it is nothing more than putting the plant in a bathtub that holds excessive water.  The continual presence of water around the root ball prevents the roots from taking in vital oxygen as well as serving as an excellent incubation chamber for fungus diseases.  It seems that most of the native soils around the country have an excessive amount of clay in them.  The presence of clay in the soil prevents good drainage, which is vital to the growth of the rhododendrons. Anyone who has ever been to the several locations around the world where rhododendrons originate knows that rhododendrons grow in shallow beds of highly organic matter.  The drainage is typically excellent.

Another cause of rhododendron death is lack of water.  Rhododendrons do not have taproots like trees: their roots grow very near the surface.  Therefore, they need frequent watering.  The acquisition of new plants in the spring requires regular watering.  During the first couple of years watering the plants at least twice a week is a must.  As the time goes by and the plants increase in size and root development, watering less frequently works well.  After about five or six years it is possible to water weekly or even bi-weekly.  Frequently sunburned leaves are the result of the lack of water.  For many varieties that have burned in the sun in the past, the cause was lack of water not too much sun.  Burned tips on this year’s new growth is typically indicative of lack of water as the plant withdraws water from the tips of the new foliage first.

Another cause of rhododendron death is the excessive application of fertilizer.  This is particularly true of applying fertilizer directly at the base of the trunk of the plant.  A good rule of thumb is to fertilize more frequently with smaller amounts, rather than one large dose.  This is especially true for small plants or newly transplanted plants.

A fourth reason for rhododendron death is planting too deep.  As indicated earlier, rhododendrons are shallow rooted plants.  Their roots grow just below the soil line.  If they are placed too deep in the ground, the soil that covers the roots serves to smother them.  I have found that planting too deep will basically stop the plant from growing.  Eventually this leads to the death of the plant.

Another reason that rhododendrons die is from cold winter temperatures.  Most rhododendron sources indicate the lowest temperature range in which rhododendrons can be successfully grown.  This hardiness rating is a guide not an absolute!  In general, the lowest temperature during the past five years is a good guide for making selections based on hardiness.  Years ago there were very few plants that were hardy in -25°F for the extreme climates.  Now we have over 100 varieties that will survive those winter temperatures.  Gardeners in the East should select hardy varieties in the beginning.  With time and experience less hardy varieties can be successfully tried.  A rhododendron rated hardy to 5°F, no matter how beautiful it is, planted in Green Bay, Wisconsin, will not survive.

As more and more home gardeners in the Southern and Midwestern states begin to grow rhododendrons, increased attention must be paid to the hot summer sun.  Most varieties exposed to unprotected all-day sun are doomed.  However, there are available rhododendron varieties that can stand direct sun.  In general rhododendrons in extreme climates benefit from filtered light and partial shade.  Planting in a southern exposure without any protection from the sun nearly guarantees plant death.

Finally, if you create the right conditions most rhododendrons will be subject to fungus diseases.  Typically we combine several fungus diseases into a general category of “die-back.”  The results of the disease are seen during the late spring when the plant is just beginning to grow and all of a sudden it drops dead.  It is also seen during the summer when a branch turns brown and dies.  Frequently the ailing plant will be lost.  These phytophthora-type diseases are generally the result of conditions created by the gardener, as it is believed that the disease spores are present in the soil all over the country.  Some of the ways that we promote these organisms is by planting the rhododendron too deep, thus providing a water culture for the development of the disease organisms.  Puddles of water that remain more than an hour after watering also harbor disease.  Watering in the late afternoon or evening encourages disease development.  Finally, failure to use fungicides during the late spring and summer encourages the development of fungus.

In conclusion, you are not alone if you have lost plants to any of the above mentioned causes of rhododendron death.  Most of the causes can be overcome with the intelligent selection of plants that are suited to your geographical area.  Finally, think about where and how you planted your rhododendrons and what you did to promote their death.