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In the 40 plus years since The Midwest Chapter was founded, members through trial and error have refined cultural practices to grow rhododendrons successfully in our harsh Midwest climate.

Proper plant selection, careful plant siting and proper soil preparation are some of the important components for successful cultivation of these beautiful plants.

The Midwest Chapter cultural guidelines on this page are tried and true practices we recommend for successful cultivation in our region. Of course, slight adjustments may be appropriate depending on your own growing conditions but the basic fundamentals as outlined have proven to be excellent guidelines.

 

 







Upper Midwest Rhododendron Culture

Most native soil in the greater Chicago area is very heavy clay compacted further by home developers. This soil condition requires amendments and modifications to grow healthy rhododendrons.

Preparing The Soil

Because rhododendrons require an exceptional amount of air in the soil, the soil should be loose, porous and organically rich with a pH range of about 4.5 to 6.0. A standard mix consists of equal parts of good top soil, peat moss, sand and shredded bark.

To prepare soil conveniently:

Planting

Large-leafed rhododendrons prefer filtered sunlight. A northern exposure close to buildings is a preferred location. Small-leafed rhododendrons, such as PJM or deciduous azaleas, flourish in direct sunlight. Protection from wind is important.

Controlling Pests

Healthy, well-grown rhododendrons are relatively free from diseases and pests.

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Winter Care for Rhododendrons

Quite a few of our chapter members live in Wisconsin and Minnesota and grow rhodies very successfully. It is important to first of all select hardy varieties and plant them in a somewhat sheltered location. Refer to "Upper Midwest Rhododendron Culture" for culturing information.

Soil preparation is extremely important. We do not recommend wrapping the plants with burlap in the winter. We found adding additional mulch around the perimeter of the plant in the winter (such as shredded leaves, pine needles or pine bark) is beneficial and helps keep the ground from freezing and thawing. You can also put some pine boughs in the ground around the plant if you feel you want to add some additional winter sun protection. With regard to snow cover, snow actually works as an insulator which is good and also protects leaves from winter sun burn.

The small leaf rhododendron varieties such as PJM and Olga are more tolerant of extreme weather conditions and perform well in exposed areas. I have found large leaf varieties become more tolerant of winter weather conditions after they have become established after a few years.

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FAQs

Pruning Azalea bushes
January 11, 2008

Question

We recently moved into a new house. The previous owner had planted azalea bushes up to 35 yrs ago and she cherished them. While they are beautiful, they are very close to the house and have overgrown the front window. We also need grading done around the outside of the house,and the azalea bushes are in the way. Is there any way of drastically trimming them down without killing them.

Answer (from Tony Greco)

Azaleas can be drastically pruned but I wouldn't cut them down more than 50% at one time to not put too much stress on the plants. If you need to remove more, consider trimming back in two stages.

Azalea roots grow laterally and close to the soil surface so if you're regrading, try to avoid putting too much soil over the roots.

I would also wait for the plants to bloom before pruning. This way you can enjoy the flowers and then prune before the growth spurt that immediately follows bloom. Fertilize the plants after you prune them with an acidic fertilizer and mulch your plants with pine bark mulch. It may take a year or so for the plants to completely revive but they should be fine.

Try not to let the plants become overgrown. It's better to judiciously lightly prune right after they bloom to keep them in bounds once they are the size you desire. Also, don't wait until late summer to prune since the next year's flower buds form in late summer. You don't want to prune off next years flowers.

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Azaleas and Rhododendrons as understory plantings
December 27, 2006

Question

I live in Northern Indiana which I believe is Zone 5. I have a shaded area under mature pine trees. The branches on the trees have been trimmed up 10' to 12' above ground level. To the immediate East of the shaded area is the neightbors pool fence which blocks some of the morning sun. To the immediate West is a garden shed that blocks much of the afternoon sun. I would like grow Azaleas and/or Rhododendrons, if possible, as part of the Understory. I would welcome any suggestions you can provide as to what Azaleas and/or Rhododendrons, if any, will grow in the above described environment.

Answer (from Tony Greco)

It sounds like you have a sheltered area you're working with which should be ideal. The pine tree should provide a nice acidic area which rhodies like but make sure the surface roots of the tree don't compete with the rhodies for moisture. Ensure your planting mix will retain moisture under the pine tree so you're plants do not dry out, especially the first year or two as they develop a root system. Refer to our web site for more info on soil makeup.

Although rhododendrons and azaleas are considered shade plants, they do require sun to set flower buds and stay compact. Any Zone 5 plants should do well for you but if you don't get much sun I would probably stay away from deciduous azaleas as they like quite a bit of light. Evergreen azaleas may be better azalea choices.

For large leaf rhododendrons, I would consider the Yakushimanum hybrids such as Ken Janek since they stay compact with beautiful flowers and foliage. These may not stretch as much reaching for sunlight since they are naturally compact. Small leaf rhodies tolerate more sun and may not be suitable for this site.

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Hardy Rhododendrons for the Midwest USA
November 13, 2006

Question

I live 65 north of St. Paul, MN. What would be the best rhodendron variety for me to grow? I planted two English Roseum plants last spring on the NW side of my house. Now I'm worried that they may not survive our severe winter. How can I protect them?

Answer (from Tony Greco)

English Roseum is known as an "iron clad" meaning it is very hardy and grows in harsh conditions. We have members in zone 4 in northern Wisconsin and Minnesota that successfully grow this variety.

I'm going to assume you prepared your planting site as we recommend on our web site (see Upper Midwest Rhododendron Culture). Make sure your plants stay well watered this fall as newly planted rhododendrons should not be allowed to dry out. Also, add a couple of inches of mulch such as shredded leaves, pine needles or pine bark mulch to protect the roots.

Direct winter sun can be a problem, especially with new plants but I don't think this should be a major concern on the NW side of your house.

We do not recommend covering rhododendrons in the winter; if planted properly and mulched well you should be OK. If you really feel you need to add some protection, put a burlap screen around the perimeter of the plants leaving the top open and fill the cage with leaves. I would avoid having the foliage rub against the burlap.

If these are your first rhododendrons, do not become alarmed when the foliage sags on cold days. This is the plant's way of protecting itself from harsh conditions. The leaves resume their normal appearance when the temperature returns to the mid thirties.

You should receive a lot of snow where you are which is good. The snow acts as an insulator protecting your plants.

As for other varieties to try, any of the ironclads such as Nova Zembla (red) and Catawbiense Album (white) should work. Also the lepidotes (small leaf) such as PJM and Olga should do very well. And of course the Northern Lights Azaleas developed at The University of Minnesota are very hardy.

A group of plants from Finland have been introduced recently that are extremely hardy. The following is a list of these Finnish hybrids that are all hardy to minus -35:

I would recommend shopping at good, reputable nurseries rather than the big box stores which sometimes carry varieties that may be too tender for a given climate.

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Taking Rhododendrons indoors for the Winter
October 1, 2006

Question

My niece rents an apt and bought 2 gorgeous rhododendra in pots for her patio. She wants to take them into her garage or basement over the winter. I don't think this is possible, is it? Can she take them indoors with normal light and keep them in her apt?

Answer (from John Golab)

Yes indeed, the potted Rhodo can be kept indoors near a window so some light is present. The coolest area inside the apartment is best. No mention of what city is indicated, so I will assume a Midwestern city with normal winter weather.

The potted plants can also be placed in a garage, potting shed, or basement provided there is sufficient light to keep them alive. They cannot survive in the dark. Artificial lighting can also be successful, much the same as germinating seeds. In all cases, water as necessary, not excessively.

One side note, the name or hardiness was not given for this Rhodo. Generally, storing the plant in a potting shed with sufficient light, unheated, will gain 15-20 degrees, as compared to the outside temperature.

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Summer Care for Rhododendrons and Azaleas in the Midwest
August 8, 2006

Question

Transplanted from a nursery a mature plant this late spring in early June, along with a vibrant azelea, should I trim either plant before fall? Any tips to ensure a good blooming season next year?

Answer (from Tony Greco)

I would strongly suggest you do not prune your azaleas or rhododendrons this late in the summer (August) if you want to maximize your bloom production next year. The time to prune is shortly after they bloom in late spring or early summer.

The flower buds most likely have either formed already or will shortly appear on your plants. If you prune them now, you will be losing this flowering potential next spring. It is also very unlikely there will be adequate time this year for new growth and bud development to mature properly. In the Chicagoland area, I have found when pruning late in the year, the new growth may not fully develop and harden off properly before winter and can be damaged.

If you have an unsightly branch or two that needs to come off, go ahead and trim it, but I would wait until next year for general pruning or shaping if you can.

I can only recommend you keep your plants well watered and mulched this year for maximum bloom next year. It is important they do not dry out, especially for the first year or two after planting, or their growth may be retarded which can affect bud development.

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Good Rhododendrons for West Michigan area
April 24, 2006

Question

My two newly planted rhodies died last fall and I am uncertain as to why. Can you recommend specific ones that like the west michigan loamy soil?

Answer (from Tony Greco)

Janet, sorry to hear about your rhododendrons not making it last year. 2005 was a tough year for plants mainly due to the drought we had. Not sure the reason for your problem but the lack of water could be part.

I trust the plants were planted and sited properly, but they do require quite a lot of water the first year until their roots get established.

You have wonderful growing conditions in western Michigan, as a matter of fact we get our plants for our chapter spring plant sale from commercial growers in the Saugautauck area. You should have a lot of choices. One variety that I see growing very well in Michigan is Scintillation. I grow this variety myself in the Chicagoland area and it does extremely well for me. Our website has a photo if you're interested in a pink. Our website is relatively new and we plan to post a lot more photos in the coming weeks.

Calsap is another beautiful plant, white flower with a dark purple eye.

Some other varieties I can recommend are Pearce's American Beauty, Janet Blair, Ken Janek and the ironclads including English Roseum (lavender pink), Catawbiense Album (white) and Nova Zembla (Red). Actually, all of the varieties on our website will grow well for you. It's really a matter of choice as to flower color, plant size etc.

I'm not sure where you purchase your plants but you may want to search out plants from local Michigan growers. I can always tell how the soil from Michigan growers is so sandy compared to the container grown rootbound plants from the big box stores.

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