A New Approach to Street Perennials

The UK debut of a revolutionary technique using perennials in public planting schemes was revealed by Bert Griffioen at the Palmstead workshop I attended recently. Bert hails from The Netherlands where his third generation family business focuses on the supply of perennials to garden centres and public space contractors across several countries in Europe.

Around 5 years ago he had a major problem as the demand for perennials fell sharply. When he asked his customers why this was, the response was cost of maintenance and the knowledge required to look after them. Bert then came up with an innovative solution: an example of the result is pictured above.

His technique is to mass plant a variety of tried and tested cultivars (typically 8-9 large plants/square metre) which can withstand close mowing by machinery in early spring just after the plants have started growing. These then grow back quickly to provide a low-growing, dense cover which suppresses weeds and reduces the need for irrigation. The clippings remain in situ, thus acting as a mulch. Great care is taken with soil preparation (even replacement where necessary), which Bert acknowledged is the key to the success of this technique.

Around 30-40 different cultivars have been identified as 'good doers' and Bert trials another 20-30 each year to see if they are suitable for addition to the mix. Choices include Salvia, Geranium, Hemerocalis, and Sedum. The kind of cultivar can also be very particular, for instance 'May Night' is the selected Salvia cultivar as it responds the best to this technique and as Bert said: the public doesn't care whether it's S. 'May Night' or S. 'East Friesland', they only see that it is blue.

Bert's company delivers the complete package design, preparation, planting and maintenance because then he knows that the technique won't be compromised and his reputation is retained. Typical costs in Holland are £35/square metre vs. £65/square metre for an annual bedding scheme. You can imagine that everyone in the room involved with public planting schemes sat up very noticeably when those figures were mentioned! I wish my local council had been there: we might have had a chance of replacing some of the gloomy green monoculture planting.

Scheme longevity was also discussed: when designs include bulbs, then 10 months of interest per year is possible and the plants can last for up to 10 years. However, some of the results shown on the day looked a bit 'blocky' to my untrained eye, but I'm sure it's possible for this to be easily addressed. As you can see from the photo at the top of this post, this roundabout scheme looks a lot nicer than most of the examples I've shown you previously. Yet it still retains plenty of visibility for both drivers and pedestrians so safety isn't compromised. I'm also interested to see there's planting leading up to each junction, which of course could be used to direct pedestrians to the safer areas to cross the road. It also ties in nicely with Ryan's OOTS post where he talked about rain gardening on San Francisco's pavements. Perhaps Bert's technique could also be used to provide a solution to rain runoff problems in our towns and cities?

It was obvious from the buzz afterwards that this talk was very well received and I understand that Palmstead are exploring the possibility of bringing this technique to the UK. It's good to be able to report some positive and innovative news about public planting for once :)

Many thanks to Nick Coslett at Palmstead Nurseries for sending me the above image, which is Copyright Bert Griffioen.

Update 6/10: I've received the following from Bert Griffioen after I'd sent him the link to this post. He adds so much great information that I'm including it here:

Thank you very much for your message, I enjoyed reading your article. You have understood very well what the technique is about.

Please allow one correction and one remark: we did not see demand for perennials dropping 5 years ago, it was the use of perennials in public spaces that had almost disappeared. The demand in the garden center market was (and still is…) growing and that made me wonder how a product that was more and more appreciated by gardeners, had lost it’s place in public plantings.

Your remark on the way we design, ‘blocky’ (there is no Dutch translation to that, but I understand perfectly what your mean) is something I might have expected. Nevertheless it has two reason: mixed perennial planting, which on request we also do, will soon, after the first year, start to look different from the original design. Simply because only very few perennials will grow at the same speed, which automatically means in the far majority of cases the stronger grower will take over. The weaker just will not withstand this and die.

By using the ‘blocky’ way, every plant will have it’s own space, in our concept for as long as perhaps 25 or 30 years. I have seen, also in Holland, beautifully designed perennial plantings, from which after a couple of years a big number of sorts has simply disappeared. Low maintenance, long lasting plantings simply do not go along with this way of designing.

Reason number two is the maintenance. In The Netherlands in many cases public spaces are being maintained by people with a slight mental disease. I’m sure you have these companies in your country as well. Knowledge of plants is simply not at hand, these people just will in some cases not distinguish a cultivated plant from a weed. This spring we have planted the roof of a big car parking, mixed, looked perfect, until the space manager reported all Euphorbia had been removed as the workers thought they were weeds….. Sometimes one needs these kind of experiences in order to feel confirmed you are on the right track…


  1. this type of planting would also work wonders as replacements for water guzzling, pesticide-riven suburban front lawns!

  2. Petoskystone - yes there's lots of possibilities :)

  3. I really like this idea - I wonder if my local authority would give me a roundabout to play with?

    I'm curious about the cost estimates though - is the £35 per mt per year an average over the lifespan of the planting? The maintenance in years 2 onwards will be less than that I guess, but the set up costs in the first year will be much more won't they?

  4. Nick - just consulted my notes and yes, more expensive start up costs was mentioned but not the actual amount. However payback on these costs was very quick.


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