Friday, 3 June 2011

To be, or not to be a Herbaceous Perennial?

Typically textbook; herbaceous plants are classified according to plant lifespan. That is, annuals, biennials and perennials, where the latter outlives the former. The widely accepted definition of the herbaceous perennial, is hence a plant that lives longer than two years. No surprises there.

However, as so cleverly argued in Noel Kingsbury's recent article in the Plantsman, entitled 'The long-term performance of herbaceous perennials', despite their prototypical portrayal and the best possible care, some perennials are just not programmed to be everlasting. For yours truly, this official revelation represents the much needed substantiation of my not being a terrible gardener with a knack for losing precious plants. Instead, it means that for some perennials, there is little one can do to ensure that they don't shuffle off their mortal coil, before their defined 2+ age status.

Monarda Beauty of Cobham (July 2009)

Perennial longevity and clumping growth habit is much favoured in our household. The Greenhouse Borders are therefore planted solely with herbaceous perennials, with the intent for their growing into one thick mass of dense border. To ensure survival therefore, plant selection is limited to the tough, sturdy plants that are able to compete successfully and survive without much (staking) maintenance. However, despite careful plant selection and care, once in a while the plan, spectacularly malfunctions. We all know that as plants are living organisms, gardening is never, nor should it ever be, unproblematic. It is after all, part of its charm. However, if through simple acceptance of convention, we are failing to understand true plant characteristics, especially in terms of their long-term performance, we are doing something wrong.

Kingsbury's article, in the June 2011 issue of The Plantsman, is a must read for every gardener. Incidentally, The Plantsman, is a much too unfamiliar publication to the amateur gardener. My recent,  negligible blog poll as to which gardening magazine was a favourite amongst gardener bloggers, revealed too high a focus on the striking glossies; Gardeners World (30%), Grow Your Own (30%), Gardeners Illustrated (23%), The English Garden (7%), The Garden (7%), Amateur Gardening (3%), The Edible Garden (3%) and the Plantsman (0%). Agreed, the articles in the Plantsmans' repertoire are pretty academic and many over my head, but nevertheless a much valued publication by yours truly. I digress, my apologies...

Through his extensively published literary oeuvres, Kingsbury's research into the forms and behaviours of perennials, is widely celebrated. In this recent article, he represents his findings from a further research project, focusing on long-term plant performance. Additional congratulations are owed to the man, as this research is part of an EU-funded project, which has to be one of the few, where valuable EU tax monies, have actually been well spent. EU sniping aside, the research was aimed at addressing cost-effective management of public spaces, though his findings are extremely relevant to the horticultural industry as a whole, and in particular, just as yours truly, to the amateur gardening punter.

Kingsbury defines long-term performance as to issues relating to plant establishment, long-term growth in plant spread or the plant diminishing over time. By means of questionnaire survey, amongst a diverse gardening population, twenty plants from a set list, were scored for Kingsbury's five key performance indicators;
  1. Longevity
  2. Vegetative spread
  3. Competitiveness
  4. Speed of establishment
  5. Spread by self-seeding
Survey respondents provided details of their garden conditions, though Kingsbury argues that long-term performance issues are genetically driven, and hence environmental effects such as garden micro-climate and soil condition, have limited impact. We know that plants thrive in some areas, some prefer sun, others shade, though I agree with Kingsbury's fundamental point, in that plants' ability to thrive in the long-term is prescripted in their genetic make-up. It is this, that makes this research so interesting, as we are therefore addressing the plants' core DNA qualities, the results of which, will help us understand and respect them further.

Through clever data analysis and (A-level/University nightmare) standard deviation tests, the tabular presented results, show the number of respondent reported indicator scores, per plant type. A wide variation of the studied perennials are just that, though the research shows that a number of so described 'less-perennial' plants also exist. Unfortunately for me, that includes my favourite, and much the culprit of my planting malfunctions, the Monarda (hybrids).

Pensthorpe Millenium Gardens 2007

I adore the Monarda and consequently, several varieties, crop up in our Greenhouse Borders; Beauty of Cobham, Croftway Pink, Blaustrumpf, Prairenacht, Schneewitchen, Ou' charm, and (believed to be, though lost the label and memory) Mohawk. Being such valued specimens, they get it all; the right soil conditions, plenty of organic matter, good sun exposure, wind protection and yet still, successive springs one is too often faced with the prospect of their being nothing there, but an ex-plant. The value in Kingsbury's research is that one is now educated to this plant's 'less-perennial' nature. The research results, showed that Monarda's spread clonally in such a way, that Kingsbury argues, makes them vulnerable through failing to set core growth. Similar results were found for Achillea taxa and Heuchera micrantha, the former also planted in our border, and just as the Monarda, a plant we have had 'issues' with.

Other plants score poorly on the long-term performance scale due to their slow establishment, meaning that they are 'easily lost in their first years'. I now understand, why one must persevere with plants such as the lovely Baptisia Australis and Dictamnus Albus, which though long-lived, take such a long time to establish, and in that process are therefore very vulnerable indeed.

Unfortunately, more of my favourites score poorly in the results. Aquilegia vulgaris, Knautia Macedonia and Echinacea are even further demoted, to 'short-lived' perennial status, as they form tight, non-spreading clumps and are hence 'unstable'. Thankfully for yours truly, the Aquilegia is a successful self-seeder, the satisfactory results of which I have recently plucked out of the adjacent garden path. There is some good news, my recent addition to the border, the Filipendula Rubra, is dubbed a 'guerilla-spreading species', able to successfully intermingle with other vegetation and hence has good long-term potential. I certainly like the idea of guerilla plants, and intend to seek out more of them. Other successful garden path pluckings, include the Alchemilla Mollis, which similar to survey respondent results, is very successful at self seeding. Some of the respondents went as far as relegating this plant to weed status, though personally speaking, that is too drastic an accusation.

One can see therefore, that if one is armed with this kind of information, we have a much better chance of succeeding in the garden with herbaceous perennials. Incidentally, the research is also invaluable in terms of specific plant selection. For example, by means of the readings on the 'Vegetative spread' and 'Competitiveness' scores, one can select plants that can stand up to super tough vegetation, such as the dreaded ground elder. Unfortunately, we have a smidgen of ground elder growing rampantly in our garden, and just as has been proved through Kingsbury's research, our Geranium (Oxonianum) stands up successfully to this super nasty.

The moral of the story is that many perennials though of great ornamental value, have their limitations in terms of long-term performance. This information is invaluable to gardeners. One can only but appeal for further education, as to which plants have stronger 'staying-power over time' and their associated trade off(s) - vigorous spreader, slow to establish, looney self-seeder etc.

Kingsbury highlights his frustration, as to the failure of reference literature and especially plant labeling, to inform the public as to plant longevity, consequently leading to frequent disappointment. I could n't agree more, though foresee potential mimicking of the excessive food labeling sagas in the supermarket trade. Understandably, I suspect that nurseries won't be too keen to label plants as 'short-lived' perennials. Though, labels should include more information as to plant (long-term) survival mechanisms, possibly following Kingsbury's key performance indicator scale. Perhaps, I can satisfy some potential anxiety for nurseries out there as to higher labeling requirements. The knowledge, that the precious Monardas are vulnerable in terms of long-term performance, does not in any way, wane my adoration for them. Far from it in fact, as it may result in a specialist nursery,  enjoying the prospect of an annual retainer.

As per the trite, though true cliche, information is king. It will be interesting to see where this research leads in future. Thank you Noel, for bringing this to our attention. I for one, am very grateful indeed, particularly as you have unknowingly restored confidence in my, no longer waning, gardening aptitude.

1 comment:

  1. Crikey! Just got back to being able to comment and I'm lost for words! What a lot of information :) Interesting stuff though.Mo

    ReplyDelete

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