Choosing our primary tree

My drylands food forest – and all four zones out behind the house – are planned around a primary tree. In the very centre or near enough to, tall, shady, able to protect the space from the ravages of daily weather. In this climate you need a primary tree, one that can help shield the many other productive plants so that their ability to produce is increased. It was a crucial thing to choose in the overall design. So I’m going to write a bit about that choice.

Ideally, I’d have worked with what was already here. And what’s here is lovely – a huge, double-trunked Port Jackson fig that must have been planted when the house was first built. It keeps the whole space cool right through hot summer mornings, until the sun manages to finally get past it. It’s what stops us from baking into biochar for the bright months of the year. Unfortunately, it was planted in the most stupid of places. As was the fashion at the time, you did a shrubby border around the fenceline and left the huge middle space as open lawn. Y’know, for backyard cricket and suchlike. It was probably a nice plant in that border, pretty variegated leaves and tough as nails. However it wasn’t going to stay a little shrub. The non-variegated stock grew around the rest of it and now there are two twenty-metre-tall trees. Planted less than 50cm from the fence. Over both neighbours’ sheds. Worse, it was planted on top of the sewerage lines. I hate to think of what blockages are going on down there. As much as I love tall trees and don’t want to have to take them out, this one is going to have to go. One neighbour keeps trying to take out any bit of it that crosses his side of the fence (almost 50% of the tree’s volume) because “it drops leaves, and my back is too old to pick them up every day”. So we needed to get the new primary tree in fairly promptly so it could begin growing and starting to reach a replacement height. And also get it right in the middle of the block, away from the sewerage pipes, fencelines and the neighbour’s chainsaw.

I spent a long time looking at possibilities. The factors I was searching on were:

  • reaches 20m in height in a feasible time
  • deciduous (both for winter light and for nutrient recycling)
  • non-sclerophyllous (so that the leaves will break down into soil humus in a reasonable time)
  • good for kids to climb
  • basically safe plant (non-poisonous, not too spiny or spiky)
  • climate-suited (essential), preferably from a similar climate or with a proven track record of growing in Perth (needs to survive summers with neglect)
  • ideally also productive and/or nitrogen-fixing, but not necessary
  • able to be sourced

We went with a Persian ironwood, in the end. My first three suggestions – mulberry, jacaranda and almond – were rejected by the landlord (who also loves large trees and was very keen for us to put in a suitable replacement tree as soon as possible). I’m not sure why. I just got a “no”. I know I considered carob and the Irish Strawberry tree, but neither is deciduous so it would have meant no winter light, and winter is an important growing season here. The moringa is an amazing tree, nitrogen-fixing, fast-growing, every part edible – but it tends to be too brittle for climbing and doesn’t make a broad canopy able to shelter others, so that was out. The druid in me resonates with oak, but oak makes shade possibly too heavy to have a secondary forest around it. Though I did think carefully about the cork oak, Quercus suber. The native tamarind, Diploglottis, looked pretty cool but wasn’t really main tree material – I marked it for a possible interesting heat-tolerant fruit tree instead.

The final shortlist I sent included the Judas Tree (from the eastern Mediterranean), Velvet Ash (Arizona), Gleditzia Sunburst, Chinese Pistachio, the Japanese elm, Persian Ironwood, the Cape Chestnut, Pistachio, and Goldenrain/Koelreuteria. Several of these I’d managed to spot around the city while making decisions, so I could have a good look at what they looked like in real life and be sure I was selecting good options. The chestnut got rejected immediately (spines). After some hemming and hawing, the landlord selected the Persian Ironwood, Parrotia persica. So, primary tree selected after six months of observation of the space. Permaculture recommends at least a year, but I needed to get it started growing because we have a timeline for losing the existing large trees. And its location was pretty well predetermined by the available space, everything else will get planted around it rather than the other way around.

The problem with spending so much care and time on a complicated decision is that you’re very aware of the opportunity cost – i.e. what you lose by choosing any particular option, usually the next-best thing. I have to admit there were some trees on the list I was sad to not have been able to plant. So I revisited my design, spending much time with sticks and sights out in what was going to become the drylands zone as well as extra time re-reading tree needs and growth details. Suddenly I found room for a Judas tree, a moringa and a male-female pair of pistachio trees along with the olive and citrus. Amazing how that happens.

The other problem with spending so much time is that the plants that were available when you started the process aren’t necessarily still available. I managed to find one lone Persian ironwood. At least, I hope that’s what it is – it was completely unlabelled, and I trust the staff at that nursery a little less now than I did back when I bought the tree (long story). But it seems to match leaf pictures online.

A young tree in the centre, about a metre-and-a-bit tall with three main stems. Each stem has large light green leaves along it. The tree is planted in the middle of a half-circle of logs perhaps two metres across. The circle is covered with straw and many small bushy green plants grow amongst it.

The Persian Ironwood (Parrotia persica) in new leaf. The bed marks a protected area where the soil’s been reconditioned for the tree’s use. Also growing there are lettuces (self-seeded), daffodils and many varieties and species of thyme. The mastic thyme from Spain is really loving the space, some of the others are finding it tough now that the seasons have swung.

It’s now been in the ground about a year. It’s growing very slowly, so much so that I find myself doubting whether it will really reach the height I wanted at any kind of usable speed. If at all – information from the Net on any given topic improves noticeably year by year, and what’s out there now seems to understate the height and speed of growth more than my initial readings. But I will cross my fingers and keep holding out for what will hopefully one day be a gorgeous tree that my grandchildren can climb.

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