For example, on the way back from our nursery visit in the afternoon we passed a long row of multi-stemmed Prunus serrula, no more than 2 years old. They were dying because the design had them perched on the top of low mounds and surrounded by grass. This was taking all the available moisture and so the trees hadn't been able to get their roots down to the now relatively lower water table than if they'd been planted at street level. It was painful to see and I was shocked when I was told the total cost of planting a tree is around £500 when taking design costs etc. into account.
Apparently this isn't an isolated incident. The main killer of our street's trees is drought stress through a combination of one or more of: poor design decisions, incorrect planting or lack of follow-up care. They suggest using the bag watering system shown above, which delivers water through a couple of holes in the bottom of the bag. Whilst it's relatively cheap (£25), I'm to be convinced it has a real place on our streets. I'm sure they'd be relatively easy to vandalise or steal.
Climate Change was mentioned, but was dismissed by Richard Bisgrove as an issue for most current/ proposed schemes as plants are much more resilient than credited. This also assumes the scheme gets refreshed in the 15-20 year timescale mentioned previously. However, extreme weather events are a different matter: an increase in soft, green, absorbant plantings should help to reduce their impact. [Here's Richard's very good article about the impact of
Last winter was seen as a 20-year weather event which impacted on commonly used plants such as Geranium 'Rozanne' (died) and Cornus alba (bark eaten by mice). Richard Bisgrove also said sugar maples could become a more viable planting option as our autumnal weather seems to becoming much more like that of the States and Canada.
The rapid spread of horse chestnut leaf miner means they probably won't be used in future planting schemes. Limes (Tilia sp.) and Dutch elm disease resistant Princeton Elm (Ulmus americana) were suggested as possible alternatives. I finally got to speak to our county arborist on Friday about this issue, which I'll tell you about in a future post.
Westminster council has 1 million visitors/commuters passing through their parks every day, so the management of the grassed areas is 'interesting'. Grass mixes suited to dry conditions [thus less irrigation needed] and wear and tear are used, plus mixes for shade where appropriate. In the winter, all grass area are hollow tined and the holes filled with recycled rubber crumb. [this approach might be appropriate for e.g. National Trust's most popular historic gardens - they often cordon off lawned areas to allow them time to recover, though I wasn't sure about the use of the rubber crumb]
Other management strategies adopted by John Tweddle at Westminster council include:
- There's a tree canopy issue in London as these, particularly the London Plane, are shading out much of the planting below. A programme of crown lifting is being carried out [also needed on the public land next to our house!]
- Increased use of drought tolerant planting
- Replacement of annual bedding schemes with herbaceous and shrub plantings to reduce upkeep costs
- Recycling of green waste as mulch - reduces the need for watering and reduces pests. This also includes the replacement of lawn mowers with ones which return the clippings instead of collecting them
- Reduced usage of drinking water [i.e. expensive] for watering e.g use of grey water. Also a borehole is being sunk at Lords cricket ground, so hanging baskets will be spot watered via water bowsers filled from there. They've also found no irrigation often leads to better displays when combined with mulching, especially with herbaceous and shrub plantings
- Use of organic seaweed extracts sprayed on plants leads to hardier plants with increased vigour and disease resistance
A number of these measures [plus a number of other non-plant related ones he mentioned] means reduced upkeep costs. A win-win all round :)
Brita von Schoenaich said that the implementation and maintenance of the design is usually outside of a designer's control and 'creating something beautiful on public land is against all the odds'. I asked her later what the main criteria were in a design brief - budget's the main one, far above anything else. I wonder if this might lead to inappropriate plant choices sometimes i.e. cheaper ones to buy and plant which may need more maintenance. I also got the impression on the day there's not much interaction between the major stakeholders in public planting, which might have a hand in some of the issues mentioned as well as those I've seen Out on the Streets?
I did originally plan another post on planting ideas, but I see I've mentioned most of them in this piece. Lots of inspirational parks and landscape architect's work were shown during the day, which I'll be researching further during the winter months so I can compile a resource guide. It seems more appropriate to do a post on planting ideas once I've completed that work.I have a post on the afternoon's nursery visit still to do - though you can have a preview via the link and they've got a cash and carry promotion on this week, well worth the effort if you're in the area - but that can be covered outside of Out on the Streets. It was a tremendous day and I came back enthused and inspired. I still don't really understand the end to end process from design brief to maintenance, but perhaps that was too ambitious for the day. If anyone out there has anything that'll help me, do please get in touch!
As well as being my last article on my workshop attendance, it's also my last one for Out on the Streets this quarter. Thanks to those of you who've contributed thus far. If you'd like to contribute, then there's still a few days left for you to do so before I compose my wrap-up post at the end of the week :)