Thursday, 9 March 2017

Nature Strip Grasslands, Diversity for the Future

This article is the first in a two part series to impart the knowhow on establishing native Australian grasslands in a garden context, specifically for nature strips in the Melbourne area.

The prairie garden style, seen here at Frogmore Gardens, Lerderderg, Victoria

Prairie and meadow styles of design have enjoyed a huge interest from gardeners in the last 20 years, and little wonder.  Who doesn’t love the delicate ballet between blocks of breeze-catching texture punctuated by drifts of subtle colour?  The most beguiling aspect of this burgeoning popularity in Australia for  me has been the almost complete absence of our native grasses, so many of which remain an untapped resource in the designer’s kit.    In Australia we have an ecotype that beautifully mimics a prairie-style sensibility - our own native grasslands - once biodiverse wonders that blanketed vast swathes of temperate regions throughout the southeast of our continent.

Our native grasslands provide a rival to the well-established prairie style, which is usually achieved with exclusively exotic species.

There are so few well-managed grasslands left that people can go and see themselves, which goes a long way to explaining their absence in our gardens.  In Victoria, where I live, less than 1% of grasslands exist compared to their previous range.  As gardeners we often ‘ooh and aah’ over rare plants we grow, the vast majority of them exotic, but there are a plethora of local, indigenous grassland plants that are just as deserving of the title.  A sound way of ensuring their existence into the future is to grow them yourself.

I set out to create a native grassland, turning my naturestrip over to native grassland plants just on 18 months ago.  The results have been incredible, I’m very pleased with the way it’s shaping up.  Aesthetically I think it a very beautiful thing, though I’m sure lots of pedestrians probably walk past it and wonder when that skinny bloke is going to mow his bloody grass.  Far more stop and linger to take a closer look, some delight further still by asking questions.  
My nature strip grassland working up to peak aesthetic

You really need to want one in order to have one, they’re not easy things to establish and their maintenance requires more ecological than gardening-thinking.  They take effort and careful planning.  I worked in bushland management for several years, managing and monitoring some wonderful little (some tiny) patches of remnant grassland around Melbourne.  The experience was a steep learning curve, requiring a horticology approach rather than an ecological or horticultural one.  It was often tough graft, but the time spent was invaluable.  Getting to know patches of grassland around your area is a great start*.  

While native grasses such as ‘poa lab’ (Poa labillardieri) have entered the collective gardening conscience in Australia for a number of years, many other grasses have missed out.  Broadly speaking, there are several genera of garden merit that make great additions to grassland-style plantings.  These include, but are by no means limited to,  the wallaby grasses, Rytidosperma spp. (formerly Austrodanthonia spp.), the spear grasses, Austrostipa spp., kangaroo grass, Themeda sp., tussock grasses, Poa spp., and plumegrass, Dichelachne spp. - as a collection of genera they represent hundreds of species to choose from.  They make up the bulk of grassland biomass, though this list isn’t comprehensive by any means.  My advice is to learn about them, what they look like and how they grow.  They’re all different and provide a myriad of textures and colours at your disposal when designing with them.

Why Should You Want a Suburban Grassland?

Apart from there not being much of them left and their aesthetic beauty, once established (the hard bit), ongoing maintenance is relatively easy.  Once you get a good coverage of grasses they are highly effective at keeping undesirables out.  What weeds do grow are easily noticed and hand pulled.  Furthermore, native grasslands don’t require any supplementary irrigation at all.  The vast majority are ephemeral - they will often brown off, almost completely, which is a an ideal time to give them a mow.   They will readily reshoot when cooler, wetter weather returns.  Establishing them well is all about getting your timing right with planting/sowing.  Get this right and you’ll only have to water your plants in - they’ll never see the nozzle end of a hose again.  

The first photo give a glimpse of before and after planting and establishment. The second is a great snapshot of colour, form and texture contrast local species can provide - all of this is without any supplementary watering. This nature strip, as all nature strips, survives on rainfall alone!

Native grasslands have huge biodiversity values, not just for the plants they contain.  Myriad insect species call grasslands home, many exist only to visit specific plants, which is remarkable.  One of many examples, I have a couple of species of native bee that visit mine which are known to feed exclusively on wahlenbergia flowers.  Many other similar relationships exist in my grassland and for every insect I identify there are probably a dozen more I don’t even see.  A diversity of insects means a large population of potential garden helpers that will often help keep the populations of other problem insects in check.  Toward the end of winter for last three years I had massive problems with aphids on a Veronica perfoliata in my front garden.  I haven’t seen any at all this year and I suspect the new grassland and its residents are probably responsible.  These unseen helpers make pest management in the rest of my garden easier.  Where they come from and how they find their way to a 2.5m x 8.5m patch of land in the middle of the northern suburbs of Melbourne is a great mystery to me, one I would like to solve, but I’ll also be content with the romanticism of wondering in the meantime.

Prepping Your Strip

Before you do anything check your local council’s rules around naturestrip gardening.  They vary considerably between municipalities, most require a permit and others may even slog you a fee for the privilege.  For Melbourne specifically, site prepping is best done in late summer/autumn/early winter, whilst aiming to plant in late autumn to winter (when rainfall is reliable and plentiful here) so get your permissions in order well beforehand.

It’s now autumn and you’re looking at your nature strip - what do you see?  There’s probably grass and likely a few different species of it.  Kikuyu is common in Melbourne’s nature strips, as is Ehrharta erecta (panic veldt grass), couch, and winter grass (Poa annua) waiting to pop up once the weather cools off.  There are likely broadleaf weeds too, such as dandelion species, flick weed, oxalis, chickweed and pimpernell, among many, many others.  The critical thing to understand at this stage is that all these plants have been dropping seeds into your little strip far longer than you’ve been eying it off as a potential grassland garden.  There is a sleeping army of thousands (millions?) of seeds just waiting to germinate and cause you grief.  The rise of grief bears an inverse relationship to enthusiasm - a parlous state that will put your grassland at risk in the future.  Avoid it as best you can.

  • Taking a close look at this stage may also reveal some surprises - on the other side of my street there’s a naturestrip with a remnant patch of wallaby grass (Rytidosperma sp.).  I find this astounding considering our suburb was developed in the 1920s.  The site in question has a large brush box growing in hard, impenetrable soil from which nothing much else grows, so it’s seldom mowed or weeded.  Local parks are also a good place to go looking for remnant patches of local grasses, especially if your park is a wee bit neglected (we have a large patch of weeping grass, Microlaena stipoides, holding its own against kikuyu in our local park).

To make the establishment of your grassland as least stress-filled as possible, your existing nature strip grass needs to be cleared and this weedy seed load dealt with somehow.  You’ve three main options on this front:

  1. Scalping the soil, taking at least the first 3 inches off, seed load with it, and getting rid of it (expensive and not very sustainable, but highly effective in controlling weed seeds).  A turf cutter does this job brilliantly well.
  2. Solarising the whole area by placing black plastic over it for several weeks in late summer - this will cook a large mount of the seeds, though not all, as well as kill grasses and broadleaves (effective on some weeds, but not all, and it looks atrocious).  Steaming might also work but I can’t vouch for its effectiveness.
  3. Herbicide is another option (judgment on the ethics of their use should be suspended for the purposes of this article).  It will clear grass and kill the weeds that are growing, but it won’t deal with the weed seed load at all.  This option requires intensive hand pulling as weeds come up, mainly during winter.

Deciding which you use will depend on your budget and the amount of effort you are prepared to put in.  The bushland manager in me saw me using the last - killing off my kikuyu with herbicide and hand weeding.  I spent a lot of time weeding, time that would make well-hardened gardeners shriek in horror.  But there are two reasons why I went down this path.

Firstly, I rather enjoy weeding, especially with a beer in hand.  The second is that hand weeding means you are down there on your hands and knees regularly, right at the coalface of your changing ecology, watching it and making observations of the little differences that emerge week-by-week.  You constantly learn about the plants and the way they grow together, often without realising it.  If you hand weed you will soon be able to tell the difference between goodies and baddies, like a weedy Poa annua seedling and a local wallaby grass seedling.  The phrase ‘getting your eye in’ applies here in a big way.  If you get your eye down to this level and pick up those differences you’re well on your way to a successful suburban grassland of your very own.

If you’ve gotten this far, well done!  Questions and discussion below - I’m happy to field any inquiries on the topic of site prep.

The next installment will cover selecting species, planting and a controversial question: to mulch or not to mulch?

Until next time, happy gardening.

A bit of spring bling in my nature strip grassland is native flax, Linum marginale, it's a stout, wirey short lived perennial. Don't be fooled by the 'short lived'. It seeds prolifically and recruits just as readily. It will form drifts in abundance if planted in the right conditions.

*Local grasslands around Melbourne.  The following list are those good for exploring and observing throughout the year, hitting their aesthetic peaks in late spring through to mid-summer, they include:

  • The northeast corner of Proclamation Park, Sylvia Grove, Ringwood, Victoria.
  • Craigieburn Grassland Nature Reserve
  • Melton Botanic Gardens, extensive areas of revegetated grasslands.
  • Geelong Botanic Gardens also has an extensive planting of native grasslands along its main driveway entrance, a really beautiful sight in mid-late spring.

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