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[Sophie]

After a couple of years offline I've come back :) There really is not much info around for gardening in Brisbane apart from you guys! Since those sad sorry seedlings I sun deprived in my unit, Ive had the luck to move to a house with a decent sized garden. Alas clay is the bane of my existence and despite all my best intentions (and pocketfuls of gold), Ive had only a few producing successes. My compost produced 11 deliciously sweet pumpkins (I think Jap), and a large leaf oregano that is really thriving. There were some rampant Tommy Toes but few now. Basil and parsley survived, though nearing the end and I have recently potted some cumquats (second attempts after the first one overexerted himself with an enormous amount of fruit and karked it). There is little shade in the yard and I am keen for some more (manageable) fruit trees. I've tried germinating all kinds of seeds (greens, flowers..) but have never seemed to have any luck both direct sow and in seedling trays... Is it the heat, ie soil too hot? What trees would you suggest for full sun clay?

[Sophie]

Thanks Dianne! I'll give your seed raising a go when I next get a chance to get the ingredients. I do love the Leprosperums... :)

[Dianne Caswell]

Your boxes should stay damp if you have the right seedling mix. My mix is - 1 Block of Brunnings Seed Raising Mix + 1/2 a Block of Fine Coir + 1/3 of a small bag of Vermiculite - Follow instructions on packs to expand and then mix the lot together. What you don't use can be kept in a bag when it has dried out. You may have a similar mix that you use or a favourite one.

[Dianne Caswell]

We planted Melaleuca Revolution Green and Gold, the gold is still there after 36years. Golden Gem, Leptospermum Pacific Beauty, Small Leaf Lillypilly's, all still growing. Also some dwarf Pines and Juniper which adds pine leaves to the mix.                                    

[Sophie]

Excellent thanks Dianne. Which native trees did you plant or would suggest? I would love to get some native stingless bees eventually so something with flowers or fruit would be an added bonus though we get bad hayfever from wattleblossoms...

I'll give the wooden seed boxes a try, can't hurt, though I would have thought wooden crates would dry out sooner?

[Dianne Caswell]

I know what it is like to have to garden on clay. We have all clay here, even our house has moved due to the dryness, especially during our 10 year drought. Then when we get a lot of rain our gaps come together again.

In regards to gardening, we have raised garden beds. If you are wanting to do some of your planting into the ground, I would recommend them. We put down newspaper and added a lot of what was called Lantana soil. It came from around Canungra area where the Lantanas still grows. We added grass clippings, Lucerne, Horse, Cow or what ever we could get to dig in. For shade we planted Aussie Natives that were fast growing, these were grown with the view of them being temporary. We also used an organic fertiliser, which was hard to find in the 70's. This was watered and all turned over until it resembled a friable soil that we could plant into.

We now have a garden which consists of Raised Beds, Terracotta Pots, Old Wooden Boxes lined with Hanging Basket Inserts. My Seeds are sown in wooden seedling flats and if you use timber the water will soak in and they will stay dark damp and cool. You can use old wooden fruit boxes cut down or old tea caddies. There are a lot of things that once came in timber.

I mainly use Tank Rain Water to water. So you can see there are many choices you can make, you just need to find one to suit your style of gardening. 

[Sophie]

Also Elaine, FYI ipads vs desktop - have just checked - I can see all the icons on the desktop but there are not additional options that come up on ipad... pity but I'll manage

Also Elaine, FYI ipads vs desktop - have just checked - I can see all the icons on the desktop but there are not additional options that come up on ipad... pity but I'll manage

[Sophie]

Thanks Dave, interesting. I will keep an eye out for white plates. The soil temp over 30 is a concern, explains alot really. Hopefully we will get some more rain... And things will start to cool

[Dave Riley]

You got me thinking Sophie -- so I went out and took the soil temperature in the shade of the plate and in full sun. 

You can do a lot with an oven thermometer.

The result: no major difference between readings this afternoon. 32C vs 35C at 2-3 cm deep.

But the seedlings seem to be doing better behind the plate than without it...so I'll monitor the experience for a time -- and if effective try to work out why.

I suspect that soil heats up at the same rate over larger areas than I assumed...and maybe cools down more slowly that we recognise. That is, it stays within certain limits relative to ambient temperature means you really need to foster micro climates to good effect. 

As we know the first burst from a hose on a hot day is scorching...so pity the soil that's out in all that heat.

Can upright plates act as a coolant? Change the air temp to their west? Can part shaded rocks? Tree logs?

If the seedlings cherished by plates take off better than those unaided I will have an answer. But for now, it isn't a matter of soil temperature.

In my head this fascintaing article seems relevant and it focuses on moisture rather than temperature. It addresses the big picture but i reckon my seedlings may get a look in.

In a dry region like the Australian wheatbelt, a decline in rainfall also means a decline in evaporation, not an increase as many people suppose.

When we talk about a decline in evaporation in this context, we are talking about evaporation over large regions like wheat fields, sheep paddocks, woodlands, grasslands and so on, not just the evaporation from a small farm dam.

When rainfall declines, the availability of water to be evaporated in the soil also declines. Quite simply, if there is little water in the soil then evaporation can’t increase.

So less rainfall means less evaporation, which in turn means less evaporative cooling of the land and the air immediately above it. To appreciate how evaporative cooling works, think about the principle behind the Coolgardie Safe or those old-school hessian water bags that have made a recent comeback in some hipster shops. Or if you prefer, think about how much cooler a lawn is than a concrete driveway on a hot sunny day – that’s because the lawn is cooled by evaporation.

In a drought, then, the relative lack of evaporative cooling means the land surface and the air just above it tend to get warmer still. Scientists call this a land-surface feedback. But that is just one part of the cascade that increases temperatures.

Where there is less rain, there are also typically fewer clouds and more sunshine. Extra sunshine means extra heat and this has to go somewhere. In normal circumstances, it would go towards evaporation from plants and soil. But with little available water it heats the surface of the land, which makes it even warmer again.

With everything pushing the temperature in the same direction, the net effect is even warmer daytime temperatures. So the lack of rainfall drives the temperatures up, not the other way around.

[Dave Riley]

"Do the plates heat up too much?' Well if we were playing 'Honey I Shrunk the Kids' I'd prefer a dinner plate between me and the relentless sun rather than to go without.

I've been interested in clay materials and prefer glazed white china to unglazed brown terracotta in regard to condensing heat. Or so my experience confirms. Shade cloth structures are Ok if you can make them  stay put and the frames don't rust.

I've also used rocks and tree logs for shade...

The issue -- with the plates --possibly is the ambient requirements of stems and leaves vs the roots..and despite what they say, I've not found mulch a great insulator to cool the earth although it protects moisture content.  After all the best coolant is water. 

Nonetheless, I've found a significant difference between the water levels in shaded clay pots and those in full sun. So I'm thinking shade is a powerful medium against evaporation even for ollas. 

That said, the advantage of white glazed plates placed vertically is that, unlike rocks,  they are sure to cool quickly because they are so thin.

Anyway thats' my hypothesis as I explore the way it works, or doesn't,  in situ.

But without shade, planting out seedlings in this weather may not be a good idea...and we've had to abandon the exercise in  the school garden.

Related is the fact that while heat may be brutal, what worsens it +++ is wind and with ex-TC Winston  a'huffing and a'puffin off the coast we've had plenty of that.

[Sophie]

Wise advice, will do. Thanks!