There's no obvious reason why rhododendrons could not be grown within the shade of fruit trees that comes to mind although I have never done it myself on a large scale. Some do grow under an old apple tree without any difficulty. Legginess in rhododendrons is generally the result of too little light, not a soil condition. You do need to insure that your soil is sufficiently acid and contains an abundance of organic matter. Direct morning sun followed by dappled afternoon shade would be the ideal. In your location, choose hardy rhododendron varieties adapted to the Midwest. Rhododendrons don't do as well as they do in the PNW anywhere in North America except perhaps for some isolated pockets, but the right varieties grown with care really can be grown well in a great many locations.

I'm not sure about the soil pH. I was thinking of buying bags of pine bark and building up a ring shaped mound under the trees and planting the rhodoendrons that way. I think pine bark is acidic. Would that work well? How deep would I need to make the mound?

The sun is pretty intense here in summer. We're same latitude as northern California. Sufficient sunshine at least for the first few years shouldn't be an issue. We get about a month of dry weather with no rain in the summer, and excessive humidity coming off the lake. Average yearly low is abut -18C

Planting into bark rather than digging down works very well although I am not sure I fully understand the exact way you intend to do this. I certainly wouldn't buy bagged bark, however, unless that's all that's available. Buying in bulk by the yard would be far less expensive. Many sellers of landscaping supplies also sell various mixtures of bark, compost and soil one of which might be even better for your purpose. Pure bark is fine as well, but try to get that which has aged and somewhat decomposed. 9 to 12 inches of depth is enough, but you will also have to mulch the roots and renew the mulch as it decays.

What is your soil pH now? I am not sure that just planting in pine bark is going to address the necessary pH satisfactorily. Yes, pine and most other conifer bark does test out on the acidic side of the scale but the effect is temporary - as the bark ages and begins to decompose most of the acidity is lost. And it takes a great deal of any acidic organic matter to alter pH to any significant degree. And I would also be concerned about building up soil levels under the fruit trees. Changes in soil levels - even as little as a couple of inches - over the root zone of an established tree can lead to issues with oxygen deprivation and root smothering, resulting in the tree's death over time. There are also issues regarding nitrogen depletion when quantities of wood products (bark, sawdust, wood chips) are incorporated into the soil that would need to be addressed.

If your pH is not satisfactory for the rhododendrons, I'd consider amending the planting area with elemental sulfur. That is the standard suggestion for lowering soil pH. It is far more long lasting and more efficient than a bark product and poses none of the other risks. But if you are attempting a significant change - more than just a few points on the pH scale - you will need to repeat the application periodically as most soils have a buffering capacity that resists long term changes. Sphagnum peat moss can also be used to amend planting holes and lower pH in the immediate area. Since it is virtually fully decomposed, there is no concern about continued decomposition, nitrogen depletion and the leaching out of acidic compounds. This is the popular suggestion for amending soils to accommodate blueberries, very strongly acid loving plants.

I would start with a soil test to see what your soil pH actually is. You can probably get one done by the Michigan cooperative extension or if not, Cornell University will do them via mail. To my mind, trying to change the soil pH enough to keep acid-loving plants happy if you don't have naturally acid soil is more than I'd ever want to do. I know where I grew up in the Cleveland, OH area, rhodies were fairly common, but I don't know how similar Detroit's soils are to Cleveland's. If your soil is clay-based you may want to plant on a mound enhanced with organic matter to improve drainage so that they don't sit in wet compacted soil, but also mulch the root zone so that the moisture stays even.

You commented on legginess. As Mainegrower said, that might be caused by too little sun, but the variety also has a big influence on this. Check out the various Yaku hybrids such as Yaku Prince, Yaku Princess, etc. They tend to grow densely and not overly quickly.

Light levels also influence how well rhodies bloom, so as others have commented you want to aim for several hours of good light. I think my biggest concern would be that they would get overly shaded as the fruit trees grew, so think about where to place them so that they will continue to get enough light even as the fruit trees get bigger and cast more shade. Winter shade is good, but in the growing season you want more light.

If you can't provide good growing conditions for rhodies, look at other types of evergreens such as the shade-tolerant coniferous evergreen Microbiota decussata, yew (if you don't have deer) or evergreen perennials. Another acid-loving broad-leafed evergreen shrub that is more shade tolerant is Mountain Laurel, Kalmia latifolia, and if the pH is good but the light levels aren't, this might work as an alternative. The blog Dirt Simple, written by a Detroit area landscape designer, has lots of ideas for using pots, lights, and ornaments to enhance the winter landscape.

OP asked about Rhododendrons and Blueberries. I believe Blueberries need more sun and a lower pH than Rhododendrons. Correct me if I have this wrong.

I see a lot of good suggestions on soil preparation here but I would like to add something. I generally don't like relying on fruit trees for shade because most fruit trees are short lived and once they die you have no shade anymore. Yes it can be 15-30 years lifespan and that seems long but if you're young like me and have at least half a century to live, you're going to have to deal with cutting down the dead tree one day. Even if you say 15-30 years is way ahead in time, it WILL happen one day and you WILL have to cut it down one day(unless you move out from your house). And rhododendrons live longer than most fruit trees and once the fruit tree dies they will start scorching from the sun(if its full sun). This can be solved by planting a long-lived tree nearby so by the time the fruit tree dies the long-lived tree will be big enough to cast shade to the rhododendrons. Sounds a bit over-exaggerating but I feel its important to think about the future as well when it comes to gardening. However I only say that MOST fruit trees have a short life-span. Some trees like the persimmon can live as much as 80 years and if your fruit tree is a long-lived variety then you can disregard this post.

"you WILL have to cut it down one day" IME the life span of a fruit tree depends on the variety of fruit tree, both species and cultivar, as well as where it is being grown and the care it is given. I observe that folks in zone 7 seem to consider fruit trees much more short lived that I consider them to be. In my neck of the woods there are commonly fruit trees older than I am, and I am well into the second half of my first century, so more than twice Heruga's lifespan estimate, with no visible evidence of impending death. I don't think it should be of concern, especially since in both the northern OH and in NH, rhodies do just fine in full sun IME.

Most fruit trees need pruning. Wouldn't the rhododendrons get in the way?

I plant rhododendrons under Japanese maples which require a lot less pruning than most fruit trees. A pole pruner works for me. Loppers are needed for fruit trees and they have a lot shorter handles than a pole pruner so trampling and broken branches can be more of an issue. Around here most rhododendrons get taller than you want a fruit tree to to get.

Thank all for all the great suggestions. Maybe this will help with identifying the problem with legginess.

I have some rhododendrons planted in my yard directly in the soil. The ones I planted two years ago, are doing well. The oldest one's about 5 year old now. Nova Zembla and Roseum have developed the legginess problem that I see around other peoples yards. These one's have been through two harsh windy winters with record -27 low for this region. So I'm not sure if that the cause or something else. They're along a 5 foot tell fence that shades them from direct sunshine. However strong winds in Winter come off the water in Winter. Summer is hot and humid, with enough rain through the year except for one month.

I realize it may not be ideal for all the reasons stated in your posts. But I don't see any other way of doing it, but panting the fruit tree rhododendrons above ground.

I think it will be better drainage and fix pH problems, and less competition with fruit tree roots.

Would this soil mix work well :

1/3 Pine park + 2/3 peat moss + some lavarocks for drainage.

above pictures taken today

The photos show the typical growth pattern of rhododendrons growing in an area with too little light. Both Nova Zembla and the Roseum series can grow to enormous size over time. They have inherited their hardiness as well as their need for a good deal of direct sun from their wild rhododendron catawbiense ancestor (definite in the case of Roseum, probable for Nova Zembla) a species that grows naturally on exposed mountain tops. The fence may well be providing important shelter from wind, but the rhododendrons will continue to stretch toward the light in this location.

Pure pine or other conifer bark is really all you need. I would, however, check into any bark mixtures with compost, etc. available in your area.The dust-like peat sold in bales is more harmful than anything else. Once it dries out, it becomes extremely difficult to rewet or conversely turns into a soggy mass that breaks down quickly and deprives rhododendron roots of the oxygen they need. There really is no need for the lava rocks. Bark mounded above grade will drain sufficiently well without any addition of rock.

How far from the trunks of the trees do you envision planting the rhododendrons? If your goal is fruit production, you will have to prune and perform other maintenance. Walking directly on the area where the rhododendrons are growing will compact the soil, something you do not want to do around rhododendrons. There is also a potential conflict between a fruit tree's nutritional needs and those of rhododendrons.

Wild blueberries do grow in and need intensely acid soil. Modern hybrids still need acid soil but not as extremely acid.

I'm thinking 5 feet away from the trunk in a ring. I aim to be pruning the fruit trees on a regular basis, and keep them around 12 feet high, and possibly shorter. So having access is a problem should the rhododendrons ever get large. But that's probably 10 years away from now, and maybe I can go with compact varieties and mitigate this problem.

I purchased some compact rhododendrons from Walmart before which claim to stay at 4 to 5 feet tall.

So that should give me 4 feet of space on the inside of the ring away from the trunk....maybe I should plant further away.

Unfortunately the fence doesn't protect from wind in those pictures. The wind usually blows towards the fence.

That's interesting about the light. I always assumed that I needed to protect them from direct sunshine. Maybe a different species, but the rhododendrons that are doing the best for me are in a sheltered north corner of the house, and don't ever seem to get any direct light at all. They look far healthier.

A lot of the larger growing rhododendrons start out leggy and then get a crown when they get larger.

"I purchased some compact rhododendrons from Walmart before which claim to stay at 4 to 5 feet tall."

Though the size claim may be correct, I would take the labeling of big box store rhodies with a grain of salt or perhaps a bushel of salt. Look them up by name from a reliable source such as a botanic garden or specialty group to find out a reasonable size expectation within a given time period. The American Rhododendron Society's plant data base gives size estimates at 10 years, but most will continue to get larger than that over time. Few plant tags give the ultimate size of a plant; usually it's a 5 or 10 year size IME. IME most of the BB rhodies offered tend to be larger-sized ones since they are faster growing and so get to a saleable size more quickly, so are less expensive to produce.

In my garden, Nova Zembla is one of the ganglier plants, and I think needs either a lot of sun or thoughtful pruning to look dense. For your other one, I don't know if it's English roseum or roseum elegans, but my roseum elegans in sun from morning until around 2 during the growing season is dense and seems quite happy with that amount of sun. It is a quite large plant, however and around here can get to 15 feet or more, so you most likely will want to prune it or move it if it is a RE rather than English roseum.

You may also discover that not all the rhodies (along with other plants) sold at your local big box store will be fully hardy in your area as many plants sold in BB stores here aren't. I often look up a plant on my phone or tablet before putting down cash if I have any question about the reliability of info given on tags.

I do think that you should consider the concern expressed by others about the soil compaction around the rhodies that will occur from pruning as they are shallow-rooted and don't like compact soil. Is there somewhere in front of, next to, or behind the fruit trees but a bit of a distance away that you can plant the rhododendrons?

In a decorative planting they look good under apple trees but anywhere there is to be a lot of pruning or other orchard fruit tree maintenance activities a thicket of brittle shrubs underneath is going to be a bother.

Even if these are dwarf fruit trees, planting the rhododendrons 5 feet from the trunks seems much too close. 8 to 10 feet would be a more reasonable minimum. On the other hand, rhododendrons are very easy to move so a 5 foot distance might be fine to start with except for the difficulty of maneuvering around them to work on the trees.

In regard to Mike's comment above, once a rhododendron grows tall enough to reach an area of open sunlight, it will produce dense growth at the end of the leggy trunks. This is not a growth characteristic, but rather an adaptation to its environment.