DIY native grass lawn

Since the millenium drought, many gardeners and homeowners have had to reconsider the traditional Aussie suburban lawn. Or perhaps, if I remember my childhood accurately, have reverted to the more traditional version, which had patches of dust and dead grass through summers, and patches of ground as hard as concrete where it was well trodden — not soft emerald-green turf year-round. Perhaps it depends on where you grew up and how much you used the sprinkler.

Some have now renounced lawns completely. A waste of water! You could be growing vegetables there! Or, alternatively, why not astroturf it or concrete it? In the 1970s, white pebbles were fashionable as a rock mulch to replace lawns (they can look great, until a sea of weeds pops up between them).

Lawns have a legitimate function. You can sit on them and relax, the kids can play on them, the dog can sun itself, etc. They also keep your garden cool in the hot summer, unlike concrete and gravel and (ugh!) synthetic fake grass. And unlike concrete, they let the rain soak into the soil instead of creating a runoff/stormwater problem. And native animals may be attracted by them.

There’s no reason you have to have one, but since water-wise native lawns are possible, you don’t need to feel guilty for allocating some lawn space, even in the midst of water restrictions and drought.

It took me a couple of years to cotton on. After spending a couple of years reading about the ecology of native plants, I came across nativeseeds.com.au who advertise seed of carefully selected and bred varieties of native grass. (I’ve listed a couple other seed suppliers at the end).

Their marketing pitch hooked me immediately, although I was an easy target, being a native plants fanatic already. Points in favour of native grass lawns include that they can apparently stay (fairly) green in hot summer and frosty winters, with little if any watering and fertilising. Many varieties need only infrequent mowing (although the mowing height should be a bit higher than your typical, dense turf, and the resulting lawn texture maybe a little rougher).

I guess what really determined me to give it a go was the state of my existing lawn. Or should I say, my weeds. Brown and near-dead through hot weather, full of broadleaf weeds and annual barley grass in winter, and with a backbone of couch grass (Cynodon dactylon) that sent its evil underground runners out in all directions, invading my native garden and vegie patches alike. Couch is often sold as a lawn grass, but I count it as a noxious weed that should be eradicated.

Front lawn and garden beds, and the brick edging that it came with. The grass looks nice enough here in spring after two wet years, but it didn’t last.

The following year. A little less verdant in the summer heat.

The thing about most native grasses is that although tough, they are slow to get going. Currently I’m waiting for a wallaby grass (Rytidosperma geniculatum) to grow up among an earlier sowing of Redleg grass (Bothriochloa macra); the wallaby grass germinated in Autumn and grew to 1-2cm high seedlings, then its growth stalled. I know it can grow at our winter daytime temperatures, albeit slowly, but I’m guessing it’s probably biding its time (and hopefully sinking deeper roots) until the spring arrives.

Wallaby grass seedlings among dormant Redleg grass in winter

But if it had to compete with fast-flourishing introduced weeds and annual grasses (which used to occupy it’s position) it would probably not have much chance. So as part of establishing the lawn I’ve eradicated the weeds first (without using poison) and it’s going well so far.

In the spirit of sharing ideas, here’s how it was done.

1. Scalping

The first thing I decided to do was scalp the soil: remove the topsoil. The reason for this was to remove the bank of weed seeds and couch grass runners. I only had a small area, about 15 square metres give or take, essentially the garden path. I used a mattock and hoe to chip off the turf, only about 1-2cm deep. (This removed soil and turf I heaped up for six months composting, then turned into raised beds for vegies elsewhere in the garden).

Scalping the soil

2. Loosening

Having been a path, the soil here was badly compacted. It’s alluvial sandy loam, and the high silt content means that when compacted and dried, it approaches the consistency of concrete. I dug it up to about the depth of a spade, although it was set pretty hard, so I used a pick. Hard work!

3. Conditioning

Despite losing a layer of topsoil, once loosened, the soil fluffed up and appeared much higher. In time, it has settled back down. But while loose, I mixed in a few improvements. First, given how fast-draining this sandy loam is, I got 15kg of sodium-bentonite clay (bought in 5kg sacks as kitty litter at the supermarket) and spread it evenly over the dug-up clods. That’s roughly 1kg per square metre. Hopefully, it’s helping the soil to hold a bit more water.

I also spread some Seamungus fertilizer/soil conditioner pellets at a rate of 50g per square metre. Not that native grass needs much fertiliser if any, but I wanted to get the soil microbes working hard and Seamungus claims to help with this. Seaweed fertiliser, rock dust, and similar things would probably work, too.

Last, I got a cubic metre of fine pine bark chips (about five-cent-piece sized) and spread them on it. Then I mixed all three additives into the top 10-20cm of soil with a garden fork and watered it all thoroughly.

The pine bark chips prevent compaction. Until they decompose, they are a porous, almost spongy (but not crushable) structure that keeps some air spaces in the soil. I got this tip from Jonathan Garner’s excellent introductory book Dry Gardening Australia.

I didn’t think about it at the time, but the scalping and the pine bark chips also have the effect of reverse fertilisation: they take nutrients away from the soil. This is good: introduced annual weeds love high nutrient levels, whereas the native grasses are often happier without them. A lot of nitrogen and phosphorous would be held in the leaves, decaying organic matter, root mat and the topsoil that I removed.

Bark, on the other hand, is broken down by bacteria and fungi, that gobble up and sequester the nutrients from the soil in order to do their slow work turning the bark into humus. Both these methods (scalping and reverse fertilisation) are recommended in Land of Sweeping Plains, the new bible on restoring native grasslands in SE Australia. On the small scale of the suburban garden, it seems economically feasible to do both scalping and reverse fertilisation, so I did.

I let this amended soil sit for about a month before sowing seed. The soil had time to settle, and the microbes time to get to work. I know that my efforts had some positive effect: the previously dry and compacted soil rapidly became filled with earthworms, doing their essential work to improve the soil structure.

In this time, weeds popped up here and there; it’s not possible to remove all weed seeds, bulbs and rhizomes. I was able to pull them out as they came up, and I’m still pulling the occasional Onion Grass (Romulea rosea) that pops up.

4. Planting.

I first planted Redleg Grass, in the spring. It’s a C4 (summer growing)* plant, and grows best in temperatures between 25° and 35° C. It’s seen in patches around the Western Plains grasslands, although I think it is most widespread on the inland slopes and plains of eastern Australia. I bought it in pelletised form, and raked it roughly into the surface. The test is keeping the seed moist for a few weeks while it germinates, and I think I wasn’t diligent enough at this (or at burying it with the rake) – some patches germinated much thicker than others.

5. Seedling care.

During the early summer while the seedlings were establishing, we had some decent rainfall. I went away for 3 weeks over new year, and came back to find the beginnings of a patchy but atractive lawn. Through the rest of this first summer I gave it regular soakings with a sprinkler. I’ve also kept from walking on it while the grass is getting established.

How it looked by new year. Seedlings starting to get established and cover the bare patches.

In the first year, I’ve read that Redleg grass typically grows a lot of seedheads. Certainly mine did as summer dragged on. The grass grows very low to the ground, but the red-tinged stalks are about knee high and look attractive to my eye. As they began to mature, a flock of Red-browed Finches began to pop by for a feed on the seed. I take that as an endorsement of my efforts by mother nature!

It’s winter. The Redleg grass still has its seed stalks, and the Chamomile sunray (Rhodanthe anthemoides) next to the path is about to open its flowers.

The next layer.

Redleg grass is a summer-growing perennial. It’s tough, but goes dormant in winter. It browns off, especially with frost. To get the year-round green native lawn so enticingly depicted in the seed catalogues, I needed a second, cool season-growing (C3)* grass.

Weeping grass (Microlaena stipoides) is highly recommended for native lawns, but our dry, sandy soil is good for wallaby grass, which I see surviving in patches even among the introduced Couch, Kikuyu and mats of Galenia weed along the river. So I got some wallaby grass “Oxley” (Rytidosperma geniculatum) to intersow in the patches between the spreading tufts of Redleg grass.

I loosened the soil with a garden rake, and in the larger bare patches scraped the topsoil aside to bury the wallaby grass seed about 5mm deep. In areas with thicker Redleg grass, I spread the seed by hand over the surface, and then watered in with a strong spray from a hose, burying the seed at least partially as the water floated the now-loosened soil and seed together in a slurry.

Once again I’ve had to keep the soil moist and pick out stray weeds through autumn as these seeds slowly germinated. And that brings me back to where I started. The wallaby grass is peeking up between the (now dormant, partly browned) Redleg grass and it should all take off pretty well in spring. (see the third illustration in this article, above).

I think this method has so far been very successful. In a larger space, it could have been made much easier (labour wise) by the use of a mini excavator or skid steer to remove topsoil, and a rotary hoe to aerate the soil. As it happens, I don’t mind a bit of heavy work on a pick and shovel, so I’m not bothered.

I’ve spent some time explaining because if you don’t know why I did all those things you might be tempted to skip them. Perhaps in some situations you would be justified in doing so. But if you under-prepare, not only will weeds and weed grasses out-compete your natives, you probably won’t even be able to tell which are the natives and which are the weeds to be pulled out. Baby grass seedlings all look fairly similar unless you know exactly what you’re looking for (and there will be zillions of them!).

To recap, here’s the short version of what I did and recommend to replace a scrappy lawn patch with native grass:

1. Scalp the topsoil, especially if there’s a history of weeds and/or fertilisers in your patch. The lack of weeds after I did this was quite remarkable compared to previous landscaping efforts, even though I only took a tiny sliver of topsoil. Larger scale revegetation projects often scalp as much as 10cm or more.

2. Aerate (turn over) the remaining soil to at least 20cm deep. This buries deeply many of the remaining weed seeds, if there are any. It also, most importantly, creates a softer soil for your seedlings to sink deep roots into. If you really think it’s not necessary, some digging will probably still be necessary for 3.

3. Reverse fertilise (and protect your soil structure) by mixing in pine bark or similar woody mulch (reasonably fine pieces). If compaction is less of a problem for the soil you’re working, something finer like sawdust might also work, but don’t use too much (being finer, with a much larger overall surface area, it’s initial nutrient-depleting effect will be much stronger). If you are sure your soil is OK (for example, if the topsoil was all removed by builders, or if lab tests show nutrients are already low) you may decide it’s OK to skip this.

4. Be patient and pull any weeds. Native grasses are slow to get going. Not only do they require some preparation, you will need to followup at first to keep the soil moist in the first few weeks, and control weeds for the first months at least.

It might seem like a lot of labour. I guess I enjoy the work and I enjoy being in the garden so it’s no great effort for me. Doing the work in a larger, more accessible area would open up the option of using machinery to speed the process. I’ve started the same process on the back lawn by loosing the topsoil and ripping the grass with a rotary hoe from the hire shop.

We’re very happy to be rid of the old weed-patch/yellow dead patch that was the garden path previously. The only external critical review has been from the birds, and as noted, the Red-browed Finches are very approving. A couple of Red-rumped parrots have also shown interest.

It’s not on a scale to make much difference to the wider ecosystem – unless more people give it a go. But it’s satisfying and educational in terms of learning about our native grasses. And… pretty birdies!

Now I’m working on a larger patch in the back yard. As I learn more I will no doubt update these recommendations!

* C3 and C4 in fact refer to the chemical mechanism by which carbon is taken up by the plant in photosynthesis – but also correspond more or less to climatic preference.

Seed suppliers

Native Seeds are pretty impressive and have selected varieties for more uniform germination, growth, etc. They have lawn, pasture, revegetation mixes and individual species for a wide range of climates and soils.

Seeding Victoria Inc. are the main seed bank for native revegetation, and supply an incredible amount of seeds. I haven’t used them yet.

Victorian Native Seed have a lot of interesting species available from their seed production area, including some native grasses. As far as lawn grasses go, their wallaby grass mix gave me good results.

I’m sure there’s others. If you know another supplier please leave a message in the comments below.

ADDITION, 2018: Flora Victoria are the biggest supplier of grassland seed for revegetation in Melbourne’s western plains area. They are able to supply in small quantities for domestic use sometimes, enquire through their website.