Written by davethetreecenters • October 26 The Hardiest Rhododendrons of All – PJM

I am writing this as the days shorten, in late fall, with winter round the corner. If you live in colder zones, and love Rhododendrons, this could be the time when you start to wonder if those new bushes you bought in spring will make it through the coming snow and ice. I know, you have tried several times, and nursed plants with scorched leaves and dead buds back to life, in the hope that they would repeat that lovely display they had when you bought them. It can be frustrating, and perhaps you are ready to give up? Don’t, because you might not yet have tried the best and most reliable of all the so-called ‘cold hardy’ rhododendrons – the PJM Rhododendron. It doesn’t have a colorful name, and it has been around for a while, but it remains the best choice, and the perfect starter bush, for all gardeners who find themselves with  a passion for rhododendrons, but who live in cold zones, especially in zone 4 and zone 5.

The Story of the PJM Rhododendrons

Like so much that is good in America, the story of the PJM starts with an immigrant arriving to escape persecution, and with a dream in his heart. Peter J. Mezitt was born in 1885, into a family of Latvian farmers. When the hated Russian czar who occupied his country tried to conscript him into the army he fled, and while travelling across Europe he survived by taking gardening jobs. In 1911 he had saved enough for a passage to America, where he met Olga, and married her. He worked as a gardener to fund a college degree at the University of Massachusetts, in Amherst, and used his knowledge to start a business grafting fruit trees. In 1923 they borrowed money to buy 80 acres in Weston, began clearing the land and started Weston Nurseries. Within a few years they had cleared 10 acres, and by the early 1940s they had expanded to 200 acres of full-scale nursery production.

Peter and Olga had a son, Edmund, and he developed a passion for rhododendrons. He had seen the wild American rhododendron, Rhododendron carolinianum, growing in Tennessee and the Carolina, and dreamed of hardy plants that would bloom reliably in Weston. Although in the relative warmth of zone 6, New England winters can still be hard, and he also wanted to bring something new to gardeners in colder zones. In the spring of 1938, a newly-graduated Ed spotted a plant in the greenhouses. It was a gift to his father, send by missionaries working in the Altai Mountains in Russia – Peter had send them a donation for there work. It was Rhododendron dauricum var. sempervirens, an early-blooming species hardy to minus 25oF.  He crossed it with his beloved American rhododendron and produced a batch of seedlings. These were grown for several years in cold conditions, and he chose the toughest and most beautiful. In 1945 it was released, and it made Weston Nurseries famous. With modesty and a son’s gratitude he called it after his father, ‘PJM’. That’s Ed at the nursery in the picture at the top.

Forming a mound of 2 to 3-inch glossy leaves, the PJM Rhododendron develops into a bush as much as 6 feet tall and wide. Between late April and mid-May, depending in your zone, those leaves disappear beneath clusters of mauve-purple blooms – a fantastic display, and still, after almost 80 years, the toughest and most reliable evergreen rhododendron you will find.

Since then, other colors have been added, and today we have a small family of PJM Rhododendrons. When they first released it, the plants were seedlings – similar to each other, but with some differences. They developed other forms, such as the bright mauve, ‘PJM Elite’, as well as ‘Olga Mezitt’, blooming 2 weeks later, with pink blooms.

In the hands of other growers, those seedlings became more new forms, including some smaller, more compact varieties. One is ‘PJM Compact’, while ‘Checkmate’ is the smallest of all. Other colors were developed too, such as ‘PJM Lavender’ and ‘PJM White Form’. Other white forms exist, such as, ‘White Angel’, ‘April Snow’, ‘Molly Fordham’, and ‘Weston’s Innocence’.

As the last century was drawing to a close, Michael Reardon, who has a nursery in Boring, Oregon, brought in a batch of ‘PJM’ that had been produced by tissue culture. These ‘test tube plants’ are more likely to mutate, and one of these had. When it bloomed the flowers were bright pink, not lavender, but otherwise the plant was identical, and just as hardy. He called it ‘PJM Pink Delight’. Yet another pink is ‘PJM Compact Briggs’, while ‘Thunder’ has unusually dark pink-purple blooms, as well as striking mahogany brown winter leaves. Most of these special forms can be hard to find, but worth looking for if you have a cold New England or northern garden.

Growing PJM Rhododendrons

Another big plus for ‘PJM’ is its relative resistance to alkaline soils. Most rhododendrons need strongly acid soils, with a pH value below 6.0. Not this one. Even in neutral soil (pH 7.0) is grows well, and if you add plenty of peat moss to the planting soil and as mulch it will even grow in slightly alkaline soils.

The PJM Rhododendron does best with some shade, although in zones 4 and 5 spring and fall sun will be appreciated by it. Light dappled shade beneath deciduous trees is ideal, but it should be light, and protection from the morning sun in winter is a good defense against the leaves burning. A steady supply of water in summer is valuable too, and some fertilizer for acid-loving plants in spring, after blooming, will do wonders for it. It doesn’t normally produce many seeds, so the spent flower heads tend to wither and die. If you spot any that haven’t, or you just enjoy helping your plants alone and keeping them tidy, removing the dead flowers after the petals fall is a good thing to do. Snap them off – don’t cut – just above the first leaf. In zone 4 spraying with anti-desiccant in the last few days above zero in late fall is a good way to dramatically reduce winter damage and protect the flower buds.

The PJM Rhododendron is an easy plant to grow, compared to most other rhododendrons. When you see it blooming away, welcoming spring into your cold garden, you will thank Peter and Ed for their creation, a fitting tribute to the gifts to this country that immigrants bring.

***If you want to check the availability of any of the plants mentioned here, go to our Home Page, click on the ‘Search’ button in the upper right, and type in your choice – both common names and botanical ones will work. If, sadly, you find the item sold out, click on the ‘notify me’ box beside the size you want, and you will get an email the moment that plant is available again – it’s easy.