One of the challenges for our garden overhaul is how much of the original garden to keep the same, and how much to change. This post shows how we added in a water harvesting feature (a mini swale) within an existing landscaped area, to enable the establishment of new plants - some local bush tucker species!
One example is in the front garden - it's a raised semicircle with attractive rocks and boulders, with a callistemon, two proteas and some kind of melaleuca. Seaside daisies and a couple of Hardenbergia tumble over rocks - as did a grevillea poorinda royal mantle until we had 2 days of over 40 degrees in January and it suddenly died. We also have rather a lot of osteospermum daisies (African trailing daisies) which are taking over and need taming. They're bordering on noxious weed status and these have self seeded from s naighbouring property - but they provide good bee fodder in spring as well as covering bare ground where little else will grow. And they're pretty. I plan to slowly remove and replace them, but better to have ground cover than bare earth in the meantime.
I got out my trusty loppers and started taking out the dead grevillea - and discovered a huge boulder that was completely covered. We had no idea it was there! It turned out there was quite an impressive row of feature rocks along the road side of this area. Clearing off the dead plant I discovered some lovely soil and organic matter that had clearly been building for many years. It was all slowly falling down the slope, catching in plants lower down and building soil. But I could also see that in heavy rain, the slope towards the street meant run off of precious rainwater (and potentially some of that new soil too) into the street.
I was curious to see how hard it would be to dig through the clay, but at this time of year it wasn't too bad, though it did get harder and drier the deeper I dug. My advice for anyone trying this sort of thing - start small, persevere and have patience! I used my mini mattock, got comfy on a cushion and got digging. I also moved the topsoil to one side, because it's good to keep that to put back on top of the earthworks after you have finished.
Two really useful pieces of equipment are an A-frame and a bunyip or water level (pictures below). Both can be made quite simply at home for very little expense and really not much effort.
With the A-frame, I attached a builder's spirit level to the horizontal strut, so if both legs are at the same level then the little bubble shows it. It's a case of moving it along the trench and checking that the bubble stays level, remembering where you placed each foot so the next measurement starts where the last one finished. Of course, it only shows whether the two feet are level at any one time, so it's possible to get a bit out by the time you've moved all that way along the trench - especially a narrow one like this. That's where the bunyip level is really handy.
The bunyip level is just two sticks the same height, joined by a transparent hose (mine is 15 metres long I think). It works because you glue a tape measure onto each stick at exactly the same height on each stick, so you can check the water level on each stick - if both sticks read the same number, they're level with each other. If there's a difference, they aren't - and the difference between the two numbers is the difference in height between the two sticks (and hence difference in height of the ground). A bunyip level can be used by one person for very nearby measuring, but you need two people to use it over any distance.
Although it's not visible in the above pictures, this swale has an overflow point - every swale needs one. It's at the back so should it ever fill up during an exceptionally heavy downpour, the excess water will gently drain into the bush behind. A swale like this shouldn't fill up all the way to the top - just enough to harvest some water, but not so much we're in danger of breaching the downslope berm (the 'wall' along the right hand side of each picture above).
The next steps were pretty quick. Firstly, I roughed up the base of the swale with the sharp point of the mattock to reduce the compaction from walking along it. We want it to be moist but not likely to hold water for too long so plants don't get too wet.
Second, I took the organic mulch that I'd saved (you can see it on the right hand side in the pictures above) and put it into the swale, and covered as much of the surrounding earth too. Because this is typically a pretty dry bit of the garden and the swale won't collect much water from up slope (which is only a small area) I planted directly into the swale - into the mulch and humus, above its base (after getting the base so level, I didn't want to spoil it by digging deeper into it! Using plenty of organic matter in the base of a swale should ensure that plants in there are moist but not waterlogged.
I planted some river mint (mentha Australis), pale vanilla lily (arthropodium milleflorum) and yam daisy (microseris lanceolata) to make this a little bush tucker track. They're so small I had to put rock markers around them so I know where they are! It's an experiment to see whether they like the conditions, but I hope that they will cope without much input now I've got their water sorted - this is a part of the garden that we often ignore. Will post an update on how it goes later in the year!
One of permaculture co-founder David Holmgren's 12 principles is to seek small and slow solutions and I guess this is very much a version of that. Fingers crossed, this one works like it should. I'll keep you posted!