Need advice on mini-ecosystem for this small yard

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Here's the part of my South Australian yard I'm having trouble with. It's 13 meters (43 feet) long and only about 1.5 meters (5 feet) wide. My wife won't let me do anything to the paving or grass, so I'm stuck with just this.

It's a dry Mediterranean climate with no humidity all year. Never snows but nights get very cold in winter. Summers get very hot, with about 5 months of continual 20+ degree C/70 degree F weather).

Because of the fence and house next door it gets no morning sun but intense afternoon sun that kills every seedling I plant there. The house next door is only about 1 meter (3 feet) from the fence, so any invasive tree roots on my side could damage their pipes and possible result in legal action against me.

Lining the fence with dwarf fruit and nut trees is easy. If I follow the shop recommendations I can only plant 4 trees, giving them 3 meters (9 feet) each. But I'd rather plant about 7-8 dwarf trees, focusing on growing upward and toward the lawn. Is it a bad idea?

Above the fruit trees I'd like 1-3 large canopy trees to maximise my food yield and to shade my yard during summer. The major problem is that EVERY single suitable tree I can find seems unsuitable: mulberry and mango has invasive roots that ruin the neighbour's drains; walnut and Japanese heartnut are toxic to the trees around them; melinga doesn't handle cold well; avocados are evergreen, which makes it harder to prune them when growing high over my neighbour's house. Can you recommend anything for this?

Finally, I want to use the ground as efficiently as possible. I don't know what I could plant there because I tried a veggie patch over summer and nothing stood a chance because the sun was so strong and required watering 3 times a day to have a chance.

Hi Tim.

That's a shame about your many constraints. Knowing about them, though, will make it possible to work around them.

My first thought when you mentioned that the grass must stay is that you might want to convert that lawn, subtly and slowly, to a polyculture lawn that fixes nitrogen. That will add fertility to your whole yard, over time. Even just some clover sown into it will improve the surrounding soil.

I would look at square-foot gardening and companion planting for your garden space. I find that approach particularly well suited to garden beds.

At the end of the day, just tend the soil. Make sure your soil life has everything it needs, and resources will be made available and moved around by that soil life.

I would make sure there's enough organic matter in the soil, and remedy the situation if there isn't. I would perhaps look into biochar, and if experimenting with that appeals to you, try that out to retain structure and microbe hotels in active soils.

I think it might be necessary to consider drip lines under a three inch mulch layer, into which you make craters to the soil surface, into which you plant. When seedlings reach sufficient height, the mulch can be crowded closer in.

I think you might also need to consider a canopy or cover that you suspend to provide a dappling of shade when the sun is at it's most relentless.

As to invasive tree roots, you could dig a trench between your trees' root zones and any infrastructure you want to protect, and put in a textile root barrier.

If I was in that position and had my current access to wood chips from urban arborists, I would backfill that trench with a mix of woodchips and the material removed, and inoculate the filled trench with a compost extract. That would act as a soil life bioreactor, nurturing the soil life we want and moving it out of the nursery into the rest of the soil. It actually can work that way. I have done it, with frankly astonishing results.

Of course, you are in South Australia, and there are probably things you can't do, like anything that encourages poisonous anything to nest around your house. I don't even know if you could use mulch like I do without incurring some horrible infestation of something or other.

But with that caveat in mind (thanks, Captain Obvious), feed the soil life. That much can usually be done largely surreptitiously.

-CK

Can you supply plenty of water? Do you have a good source of mulch? What is the soil like?

You can plant dwarfs closer if you keep them pruned and watered.

I don’t think you have room for a traditional canopy tree. Maybe a standard sized fruit tree. Really, I wouldn’t do that even. How about an overhead trellis with grapes or Kiwis?

Do blackberries and strawberries grow there?

I have a narrow strip between by brick front porch and my sidewalk. Everything baked there until I planted thornless blackberries. They grew fast enough to shade the bricks, so they didn’t get too hot. I also put Earthboxes and other planters in front of the bricks for shade the first year.  Now medlars and a cherry bush are growing there too. I planted morels underneath it all don’t know if it worked yet, but I’ve got some kind of white mycelium. Morel season any day now though!

I'm thinking of a mulberry tree by the fence, in the middle. If I let it grow on an angle and very wide, it could shade the yard while maybe still letting enough light for the other trees.

I wish I thought about this stuff when I was younger. I would have moved to a more remote place with an acreage where I didn't have to worry about these sorts of things!