I occasionally reference a chart that supposedly tells me what to sew when in SEQ.
But I always think that sewing here is something you wing as the challenge is either determined by those too hot or those too cold (& maybe frost) times.
Effective use of shade will cool a patch.So it is so easy to cheat the seasons.
Indeed if you look at the temperature range for Brisbane the seasons -- in the traditional European sense -- aren't really there:
This sort of climate is reflected in soil temperatures which are still quite balmy. Today the soil at the Brisbane Airport was 21C to 24C at various depths to 1 metre.(LINK)-- despite the air temp dropping to 16.4 overnight.
Add other variables into your planting regime -- elevated beds, mulch cover, level of moisture/irrigation, wind exposure/protection, shade level, amount of sunshine hitting the bed, etc -- then things are not as straightforward as they may seem.
I was interested in these factors not only as a guide to my own sewing but every day I get into our plunge pool and I log the water's temperature: with more than a chilled gasp. Today the water temperature was 24C when I submerged.
I also have indoor and outdoor thermometers.
Where we are, weather is effected by the proximity of the sea -- just as our 'soil' is partly ruled by the properties of the sand beneath us.
With your own bio-engineering in mind, any kitchen garden is sure to foster its own micro-climate. We do the same with seeds too -- right? -- we trick them into growing by nursing them with special care in special places or buy them as seedling ready to go..
In the Northern Hemisphere warming the soil has a long tradition: row covers, cold frames, etc -- getting a jump on Spring. Even in our region, the Maori added stones to their sweet potato mounds and faced them north --sometimes harnessing the heat from composting activity inside the mound.. Here, all I can find that may be useful is the fact that the darker the mulch, the more heat the soil will absorb.
For instance, cover your beds with straw and much of the solar heat will be radiated back into space because of its light, yellowish color. This is why row cover plastics are black.
While we can tweak it , the guidelines we are so often offered for our local climate don't always make sense. Corn for instance is recommended to be planted from September to February but in Iowa (USA) they plant out their corn when the soil temperature reaches 10C. Elsewhere cucumbers are sewn at 15C soil temp.Potatoes the same -- but then it is the temperature range that matters for these veg.
Of course a starting temperature in the soil or air will rise or fall and that's the assumption we make with 'seasons' in mind. but if your soil is warmer(or cooler) than you think it is --for whatever reason or manipulation -- then all power to you.
And I suspect that soil in pots will vary even more than in-ground gardens. And the size of the pot will make a difference too.
I like to go down to Mt COOTHA and I Figure if they are growing it then I Should be able to as well as it's not far away.
Certain temperatures are important for germination but I have been learning more about optimal temperatures for growth and fruiting more recently. Tomatoes that weren't fruiting a few weeks ago have flowers setting now. Pumpkins are sending out female flowers again and the passionfruit has lots of fruit now. It's cool enough for green beans now too. Most plants have a range in which they thrive, and outside that they slow down or struggle. I find it fascinating.
On gardening Australia when the went to a seed growing nursery it was mentioned that some seeds need light to sprout but did not go into detail some sprout seeds in flats and then transfer into the smaller punnets .
And another fascination is the extended range of some species as I read about what plants members are planting or harvesting from at any given time. That my Tromboncinos are thriving in what I consider out-of-season for cucurbits is yet another case of unlikely yet successful planting of something I read about here on BLF for the first time for me. This is one of the many benefits of BLF and our sharing of experiences to learn from.
In comparison, the AVERAGE Summer temperature in London -- as in England -- is 19C.
Check out Average 30cm Soil Temperature Data (1971 - 2000) for GB overall: LINK.
London has longer days in summer then Brisbane that may help with some crops.
As an aside, the Parisian market gardens of the late 19th century supplied, not only Paris, but London, with vegetables grown ingeniously within the city limits. As well as cloches (pictured at right) and the like they warmed their soil by layering it over collected stable manures which, as they broke down, created composting heat.
"What chiefly attracts the gardener to the great cities is stable manure ; and this is not wanted so much for increasing the richness of the soil — one-tenth part of the manure used by the French gardeners would do for that purpose — but for keeping the soil at a certain temperature. Early vegetables pay best, and in order to obtain early produce not only the air but the soil as well must be warmed ; and that is done by putting great quantities of properly mixed manure into the soil " --LINK
Geothermal is an option for heating the ground deeper down stays warm does not seem to get any recognition in Australia on the program dirty jobs they show drilling a bore hole that they put a loop tube in and then fill with geothermal grout and air is pumped through the other way is to put a network of pipes under a green house but in Brisbane probably does not get cold enough to make cost effective.
Charles Dowding, proponent of no-dig gardening in the UK does excellent videos on YouTube and he shows how he raises seedlings to get an early start on the season. He has a specific compost pile with lots of stable manure, on top of which he puts trays of seedlings to germinate. He monitors the temperature carefully. Obviously the same could be done on a smaller scale with a propagation heating mat but he has a market garden and needs to germinate hundreds of seedlings at a time.
I can't find an equivalent chart for SEQ but here's one for NSW: LINK. -Average Monthly Soil Temperature (C ) 1980-2006 at Tocal -- which is NE of Newcastle. Some interesting figures in frost prone country with a chill factor.
I had a soil thermometer a couple of years back but it fell apart. I may deploy my oven/meat thermometer as an substitute experiment. This time of year --given the prevalence of the warm air, it seems like a useful project.
The LINK to daily soil temps at Brisbane airport is well worth monitoring as a relative indication to your own patch's possible temperature.
Even in Warwick the soil is still warm.
When I plunged my beautiful beefcake body into the pool today, just below the surface temperature was 29C. With mixing it fell to 27C. For a good part of Summer here, the shallow waters of Moreton Bay in our region were like swimming in the warm ambience of urine.
Even there the current water temperature of Deception Bay today is 25.6C.
Just so you know, soil temperatures at the airport today are (5cm-1 metre deep):
Warm still underfoot.
Warwick is down to 18.5 - 21.5C. So if your plants think its still Summer, you can't blame them.