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Avoiding cultivar confusion:

September 27, 2010

For many years I (Tom Ogren) have been collecting data on which exact landscape plants are male and highly allergenic. I collect this data so we will know exactly which plants NOT to use in landscapes. At the same time I have also been collecting large amounts of data on which horticultural cultivars already in the trade are female, permanently juvenile, or otherwise pollen-free (PF)

I have also spent years researching multitudes of native plants, looking for over-looked species where with a bit of horticultural ingenuity, we could soon enough develop many more pollen-free cultivars (selections). During all this time I have also been propagating a number of very interesting new pollen-free selections that I myself found.

Recently I have started to engage in serious talks with a number of large wholesale nurseries to get The Allergy-Free Garden Collection© ready for sales to retail outlets. I am only talking to nurseries that are very productive, very well organized, long established, that grow a large diversity of plants, and only to nurseries that are of the highest reputation as to quality and integrity.

The aim is to put together a large collection (which will be called The Allergy-Free Garden Collection©) with a great deal of biodiversity, diversity of species, and also a huge diversity of individual cultivars. Included in The Collection will be a great many extra-useful and extra-attractive female cultivars. In addition there will be many selections included that are not female per se, but that are still, nonetheless, pollen-free selections. Again, with these plants also, strong emphasis will be placed on using only the best selections.

In the past decade landscapers, landscape designers, landscape architects, city arborists, and others involved in the landscape trade…they have often found it difficult, sometimes impossible, to find all the plants they’d like to use when creating allergy free gardens and landscapes. Retail nurseries themselves have often had great difficulty in locating female or other pollen-free plants for them to sell. The greatest problem allergy free gardening has had has been availability of the best possible plants.

With the creation of The Allergy-Free Garden Collection© the availability problem will be solved. The entire collection will be branded and each plant in it will pass through a strict certification process. Professionals and homeowners alike will finally be able to go to a local retail nursery or garden center and find all the allergy-free selections they need. Included in The Collection will be grasses, vines, flowers, and of course, many trees and shrubs.

There is an unfortunate situation that often pops up in the wide world of horticulture; some call it “cultivar confusion.” What this means is that sometimes when one buys a plant and the tag on the plant says it is, as way of example, ‘Royal Apricot’…sometimes what they actually get is some other kind of apricot tree, but not ‘Royal.’ You might just as easily purchase a tagged tree that is sold as ‘Blenheim Apricot’ when it is not. In the trade, these cultivars have long been mixed up, confused.

The problem of cultivar confusion is not so serious when we’re simply taking about which kind of apricot tree it is, but with other plants, the confusion can indeed lead to real problems. A real life example: A decade ago I helped to landscape the American Lung Association Headquarters, in Richmond, Virginia. They wanted a diverse, but very low-allergy landscape. I did all the plant selection for the landscape, and the intention was two-fold, to use only plants that ranked OPALS™ number three or better. In addition, we wanted to use as many plants as possible ranked as number one, pollen-free female selections.

Included in the plans was a long row of Taxus japonica, near the entrance, and we used a selection that we knew was always supposed to be female…one called ‘Densiformis.’ The local nursery that provided us with these attractive shrubs said that yes, they were indeed as tagged; they were ‘Densiformis.’ Now, since the original mother plant that supplied all the cutting for the cultivar that was named ‘Densiformis’, since this plant was female…one could assume that all ‘Densiformis’ would also be female selections.

The plants were purchased, the landscape was installed, and everyone was highly pleased with the results. This was in the fall. However, six months later I came back to Richmond to give a series of talks, and when I looked at the landscape… all the ‘Densiformis’ yews were in bloom, and every last one of them was a male. All of them had to be dug up and tossed, and then replaced with a different cultivar, one on which we were able to find actual female flowers and no male flowers.

So, what had happened here? Had the local nursery lied to us? No, they had not. They’d sold us what they thought was ‘Densiformis’, what they’d bought as that. The problem was that the wholesale nursery that sold them the plants, they had mixed up scion wood from one kind of yew with another kind. No doubt, they probably were selling some cultivar of yew that was supposedly male, that was actually female. They had mixed up the material in their propagating sheds.

This confusion in assigning the correct names to cultivars is actually all too common, and it affects the naming of cultivars from numerous species. For decades now I have made a practice of visiting as many good arboretums as possible. At a decent arboretum they will have the plants tagged with the correct genus, species and cultivar name. They will also have considerable biodiversity of both species and cultivars. Perhaps most importantly, they will have these plants growing in the ground, and often they will be fully mature plants. Looking at them one can see the form of the selection, can see how large it becomes with age, and because it is often old enough to express sexual maturity, the sex of dioecious cultivars can be determined.

But it isn’t as simple as going to an arboretum and recording what you see, because sometimes when you go to a different arboretum and you read the tags…ah, you find a selection that is supposed to always be, for example, a spreading, low-growing female plant…and although the tags are the same…the plants are not. What has happened here is that the arboretum itself, at least one of them, simply has the wrong information on their tags. The nursery that supplied the plants to them may have mixed up their tags. The result is confusion.

When I wrote Allergy-Free Gardening I did not include recommended female plants whenever I had already found that sometimes with that cultivar, the clones were confused, they were not always, consistently what they were supposed to be. In a few examples covered in the book, where a particular cultivar might have been very useful, I recommended that the readers only buy that selection if they actually saw any fruit on it…proof that it was probably the correct cultivar, and was female, hence pollen-free.

Simply to explain the problems inherent in cultivar confusion, and how they might impact a landscape being designed for people with severe allergies and allergic-asthma….it is hard enough just to explain the problem in a clear, easily understood fashion. But to design and plant a true low-pollen or pollen-free landscape, an allergy free garden landscape…the designer needs to be able to buy plants that he/she can trust to be exactly what they are supposed to be. This is one of the main reasons I am now working with these large growers to assemble The Allergy-Free Garden Collection©.

As we add every new plant to The Collection, we will first make sure that it will be exactly as it is tagged. Mature plants of each selection will be observed, over time, to make sure if the cultivar says it produces no pollen, that it is indeed pollen-free. When plants are being propagated, only one species will be done at a time, and only one cultivar will be done at a time. Every single plant in The Collection will be certified to be exactly as tagged.

It is entirely possible, in fact it is almost a certainty, that once this big Collection of female, pollen-free, and otherwise very low-pollen, allergy free plants is announced and released to the public…that it will soon be copied by other propagators and other nurseries. However, at that point we will have no control at all over the accuracy and integrity of those growers. The plants they will sell as pollen-free may well be, hopefully, but then, they might not be, especially if they fall victim to the existing confusion within many of the landscape cultivars already in the trade.

Often the only plant materials that the buyer can purchase with 100% certainty of getting actual allergy free plants, will be those from The Collection, and all of these will have tags with the logo of the word POLLEN, in bold face, inside a circle, with a slash drawn though it. Likewise, all plants in The Collection will be labeled as part of “The Allergy-Free Garden Collection.”

The Collection already exists, and new plants are being added to it almost on a daily basis now. By the time of its release to the public, there will be many hundreds of different allergy-free selections in The Collection.

One last note: Growing landscape plants, especially woody plants, shrubs and trees, is not an instant proposition, it takes time. Even though at the moment, The Allergy-Free Garden Collection© is not yet available for sale, there are still many wonderful possible choices that can be made. Any known female cultivar from a dioecious species that has any fruit or seeds on it, for example, will be a pollen-free selection. Any species of plant that is perfect-flowered and that has a low (1-4) OPALS™ rating, will be very useful in a low-allergy landscape.

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