Here is the weather forecast for Canberra's coming summer. It will be hot, with periods of cold as the sea mist drifts in. It will be wet, then dry, then very dry, then wet again. Some years it's hotter, wetter, or dryer, but weather in the Canberra region is always a basket of extremes.
Which is just what downy mildews adore.
Mildew will attack your zucchini, melons, pumpkins, cucumbers, apples, grapes and much else. It thrives in alternating hot and wet and hot or cold and dry. Leaves crinkle, shoots die, and then the whole plant dies, or in the case of grape vines, the entire plant decides to forget the rest of summer and go dormant till next spring.
There is a preventative, however, though you won't find it at the garden centre, as no one can profitably package it for plant sales. Its milk. Plain, full-cream milk, one cup mixed with two cups of water, sprayed under and over leaves twice a week. Don't use skim milk or fat-free milk, and don't spray more often, as too much dripping onto the soil may affect soil microorganisms, and stunt the plant. Aim for a thorough but not dripping cover.
There are several theories about why milk spray works. One proclaims that the protein in the milk reacts with sunlight, killing the spores. Another contends that the fat in the milk covers the healthy leaf, leaving less leaf for the mildew to colonise. The milk fat may also cover the spores, rendering them incapable of increasing. The true reason may possibly be all of these in combination, or none.
But it works, reducing downy and powdery mildew by about 90 per cent, ie; not totally, but enough for you to still get a decent crop. Sadly, milk spray alone won't prevent black spot on roses. Try adding two teaspoons of bicarb to milk spray for better success. The Rose Society of the USA used to recommend the following organic spray. (They may still do - I haven't looked up their recommendations for a decade or two.) Mix three teaspoons of bicarb with 2.5 tablespoons of PestOil (a commercial oil-based spray) then mix into 4.5 litres of water. Spray every four days for two weeks then once a week.
Black spot spores overwinter either on the dead leaves on the bush or on the soil. They incubate when the leaves are moist for four hours or more. One good evening dew is enough. Cover the bare soil by spreading with thick mulch every spring or late winter. Prune off ALL old foliage every winter. Add sulphate of potash to the soil for healthier plants, and/or spray weekly with seaweed foliar fertiliser - follow the directions on the packed or bottle.
Back to the fruit of the vine. I love vines. I also love every fruit and veg that grows on vines. You can plant them at the edge of the vegie garden then let them take over the lawn (they will be a bit more mildew prone in humid, long grass). They will happily clamber up and over the carport, given some sticks to support them up the walls. Vines can occupy any horizontal or vertical space you don't want, including a pile of weeds. Ours mostly seem to climb the lemon trees, possibly because we have lemons growing by the vegie gardens - both lemon trees and vegies like to be well fed, and so share their tucker. All vines, from melons, pumpkin or cucumber, need good feeding.
Summer vines also like long, frost-free summers, and that, sadly, our climate cannot guarantee. Luckily there are now fast-maturing modern hybrids. While I usually prefer growing plants that will grow true to type when I collect the seeds, it's worth growing hybrids to have a good crop of melons in the Canberra region.
Rockmelon Charentais 'Sultan' F1 is a modern hybrid of the old French classic, beloved for having possibly the richest flavour of all. You can smell a Charentais melon across the room. (Never leave a cut melon in the fridge except in a well-sealed container, or your cheese, tofu or even hommous will taste of melon too, which is not a good flavour mix.) Watermelon 'Conguita' F1 has a black skin, and seeds, but an unsurpassed rich flavour .
Plant any of the early-cropping melon seeds in late October - assuming a spell of warm weather - and then again in December, and you should be eating fresh, extraordinarily delicious melons from February till April, or the first really whopper of a frost.
I find apple cucumbers - any variety - crop earlier than the green kinds here. The greens have a better texture - unless home grown. Don't let your apple cucumbers get too vast, or their slices will be flabby.
Bush pumpkins - as opposed to the gigantic sprawlers - may just give you roast pumpkin by mid-December if fed extremely well and in a sunny spot. Look for Early Grey Bush pumpkin of you can find it. It has all the dark orange richness of its Ironbark ancestor, and keeps excellently, and you don't need an axe and 10 years of muscle-building to cut it.
I have no advice at all for early zucchini. I usually grow several varieties to compare growth, mildew and fast cropping. But yellow, scalloped, striped or the round zucchini which are my favourite all seem to crop about the same time - the common green zucchini might just beat the others by a week or so.
Zucchini 'Nitro' lives up to its promise of fruiting to late autumn when other bushes have gone to mildew. By then, however, we don't want to see another zucchini till October, which is when I get a craving for zucchini slice, which means I plant far too many bushes every spring. I still haven't learned that ''many zucchini'' doesn't equal ''early zucchini''.
Just remember to use ''milk spray'' at the first sign of curling whitish- or brown-edged leaves. Alternatively, plant successions of new seeds every six weeks or so. The best defence against mildews is a well fed, well mulched and vigorously growing plant, and that means a young one. Humanity (sometimes) becomes wiser with old age. Elderly vines just succumb to leaf blights.
This week I am:
- Looking out my study window at a sea of apple blossom, and hoping the bees have enough fine, balmy weather to do their pollinating.
- Watching Bryan haul out the lawnmower. No actual mowing yet, but at least the mower is by the front door.
- Mulching, weeding, and wishing that the grass seed I scattered on drought-bare paddocks didn't drift so far i.e. into the veg garden.
- Trying to work out where to plant the three potted date palm seedlings on the bank where our single large date palm gave us fruit - with no male pollinator - two summers ago in the bushfire heat. Hopefully one of new seedlings will be a male and in hot years we may yet be cheered by a date crop when the apples drop to the ground. Only another 10 or so years to wait...
- Checking the growth of the new fruit trees, all doing nicely thanks to the obliging rain, and counting the peaches, plums, damsons and cherries that have already set fruit.
- Dreaming of mid-summer corn, basil, tomatoes, cucumbers, zucchini and late summer melons, plus a host of sunflowers ...only a week or two to go till planting.