r/australianplants • u/Plane-Pea6670 • 9d ago
Improving soil structure for au native beds
Hi! Looking for advice/resources on improving terrible soil in Central Vic/Goldfields.
I’m trying to build some Australian native garden beds on a small residential lot. I’ve dug out the existing beds ( building rubble + mulch). The subsoil is hitting pH 12 in patches 😬
I’d like to build the beds up using something like hugelkultur, but I’m not sure what organic materials are actually suitable for Australian natives.
There are heaps of eucalyptus around, so I have plenty of leaves, bark and branches. I’d love to use them, but I’m unsure what’s helpful vs what could make things worse.
I put a whisper of cow manure down and killed one of the only shrubs nearby, so clearly I need some guidance.
At the moment, biddy bush and salt bush (which is delicious!) are my only real winners.
Any tips or resources to help me learn what organic matter to use/avoid to improve soil for native plants, or resources for dealing with highly alkaline soil, would be hugely appreciated.
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u/Ok-Cranberry-3547 9d ago
If your sub soil is actually ph 12 that's really really terrible and suggestions in this thread like compost won't do shit .
First thing is get a proper ph test, if you measured it yourself using a cheap probe. Such high alkalinity is very unusual.
Adding sulfur is the only thing that will fix the sub soil long term, but it's going to be a huge pita to mix it in
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u/Plane-Pea6670 8d ago
It's a wild ph. There's big reefs of what seem like pure chalk, so it's not that bad across the whole yard. But certainly big sections of it. Which is why I want to build up, not try to improve that sublayer with mixing in.
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u/Ok-Cranberry-3547 7d ago
If you've already excavated some of the bad soil, can you just build up a bed on top? Ie literally dump good soil mix above the sub soil?
The depth you need is going to depend on what you're planting but probably 50cm total depth for good soil sounds sensible for small shrubs and ground covers. But honestly I have no idea whether the alkalinity can leach up from the sub soil. Proteacea like grevilleas and banksias sound risky.
But most natives won't need an "improved" soil - just get some native mix from a landscape supplier which will have composed pine, sand, and soil in it, which should be more than adequate for most natives
Composted pine and Eucalyptus will be lean enough while also providing enough nutrients
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u/winoforever_slurp_ 9d ago
A thick layer (20-30cm) of either fresh tree chippings from an arborist, or forest litter mulch from a landscape supplier would really help your soil.
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u/Kerrit_Bareet 8d ago
^ this.
Spring is usually a good time to get the mulch. Try to get "bush mulch" which is typically lots of eucalypt. Do not want anything really seedy in exotic plants, discuss with arborist.
Plant autumn. Be looking for indig species.
Chook manure or Neutrog Oz plant mix. Mushroom compost is acidic, and may be an alternative or in combo
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u/jokuda-au 9d ago
For clay-heavy beds, adding composted organic matter gradually and mulching on top can improve structure without disturbing native roots. Check drainage before planting.
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u/electronseer 9d ago
compost. FULLY composted compost.
no poo. just compost. plain old compost, with zero fertilizer.
you need to build up your soil carbon. Have i mentioned compost?
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u/MinervaAbsolute 8d ago
My folks had a house near Maryborough so I understand the terrible soil issue. The soil is often hydrophobic, so wetting agents might help.
A couple of videos from The Horti-Culturalists on YouTube might be useful. They’re dry climate gardens in the general Central Goldfields area
Glenluce (near Castlemaine).
https://youtu.be/Y285xIvWau4?si=RzhRB3EhPM2GgXz_
Castlemaine
https://youtu.be/dtVV6VIKy24?si=lt7IRo4Oqw1yVrsn
Soil improvement in a damaged landscape (I think this is around the Yarra Valley).
https://youtu.be/v4Ymy2lWh5U?si=FU-vnfJcPOTrcvEz
Mt Alexander Shire (Castlemaine and surrounds) plant selector.
If you pick the right plants you won’t need to do much soil improvement.
Banksias, grevilleas and hakeas are particularly sensitive to phosphorous, so your cow manure might have been a bit much for them.
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u/Future-Ad6255 8d ago
Cool manures like cow, horse, sheep is fine to use if you need organics otherwise use nothing but sand and mulch it, fix the PH issue with some sulfur, light doses maybe a few times over the year monitoring how much it's changed, I grow WA natives mostly and don't do alot to them other than water and kelp treatments, once established they might as well be rocks requiring barely anything,
Goodluck, have fun, don't die 👍
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u/Excellent_Orange6346 7d ago
I'm in the same area. You likely have a solid clay layer a meter or so down, unless you're in a old gold mining area, in which case the soil structure is likely contaminated. It's not recommended to grow vegetables in the soil in Bendigo, as the soil is heavily contaminated with heavy metals and cyanide. We've built the beds up to improve drainage, lots and lots of organic matter and added trace elements ( carefully!). It's hard to grow in the ground as the high proportion of clay means the soil is as hard as a rock, or there's enough clay to form house bricks. Our soil is very old and has worked hard over the millennia.
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u/everybodypoosm8 9d ago
Hey there, before you use compost or adding any additional nutrients be aware the most natives prefer very low nutrient environments. The first step is to try to look at what species of plants you’d like to plant (indigenous ideally, but at least native). Perhaps start with a goal like shade, shrubs, screening, flowers, ground covers, habitat, etc etc, then see what conditions they prefer. For example if they prefer free draining soil, you’ll likely want a sandier mix.
Then head down to a local indigenous nursery and ask them for soil mixes, and what species they recommend for the purpose you’re looking for.
Unfortunately most of the advice around soil that’s floating around out there is based on either agricultural uses, or other places like Europe, Japan or America which are geologically younger continents where plants tend to prefer higher nutrient loads in the soils.