Last night was unusually cold, and we had frost where we had not had any for many years. If plants in your garden have been damaged by frost, please resist the temptation to prune back the damaged parts. They may look unattractive, but there are probably more frosty nights to come, and the damaged parts will protect the plants from further damage. Pruning damaged plants is best done in spring after the weather warms.
If you have plants that are frost intolerant, you can protect these with a temporary cover. See: Cold and frost protection.
Seedlings are very sensitive to frost. You can provide protection for these by making a simple cloche. See: Cloche for seedlings.
With very cold weather set to continue over much of Australia for some time, gardeners can protect young seedlings with an easy-to-make cloche. This simple structure named for the French word for ‘bell’ keeps plants warm on chilly nights and can be easily ventilated so that they don’t get too warm during the day. When the nights are milder, the structure can be easily folded and stored until it is needed again.
Instructions for making cloches can be found here: Cloche for seedlings. ** And remember to leave frost-damaged parts on shrubs until all risk of frost has passed. They may look unattractive but the burnt portions are protecting the plants from further damage.
Chilly days and nights after a brief period of perfect gardening weather occur every year in many parts of Australia. Australia is the only place where spring is said to start on the first day of September. Everywhere else, spring starts at the equinox when day and night are of equal length. This year, the spring equinox occurs on September 23rd.
Unfortunately, Australia’s deviation from world-wide practice tricks some gardeners into planting out seedlings while nights are still longer than days and soil is still too cold for root growth of warmth-loving plants. The problem can be solved by placing this simple cloche over beds that contain cold-sensitive seedlings. See: Cloche for seedlings.
Some gardeners may not be sure whether they are in a Temperate or Cool climate and, where frosts occur, the position of a property within a neighbourhood (the microclimate) can affect how much frost may affect your garden. The diagram below indicates where frost is more likely to affect parts of your garden.
The position of garden beds can also have a marked effect on the amount of plant damage that frosts cause. Cold air, like water, always flows downwards; anything that blocks the downward flow will result in frost damage in that area. Buildings, solid fences and shrubbery, and flat land at the bottom of a slope can all allow cold air to pool, and plants in these areas are more likely to be damaged by frost.
In temperate climates areas that can be affected by frost, gardeners may find it helpful to use the guide for ‘cool climates’ in autumn and winter and use the ‘temperate climates’ guide in spring and summer because the world’s climate is changing and we have recently experienced harsher winters and hotter summers. It appears that the standard climate zones may have to be adjusted slightly in future. If unsure about what to plant at a particular time of year, a reputable local nursery will have suitable plants in stock and be able to advise you on what is best for your local microclimate. Be cautious though when buying seedlings from Australia-wide nursery chains, as some tend to send the same seedlings to stores in all climate zones.
By the way, advice to orient beds in a north/south direction to allow plants to receive ample sunlight comes from northern hemisphere gardening practices and only applies to very cool climates in Australia. Most areas of Australia get more than enough sun to ripen crops. In fact, plants can benefit from some relief from harsh afternoon sun in warmer climates during summer months. It is more important to position beds across any slope in the ground to ensure that all plants in a bed have equal access to water. Avoid placing vegetable garden beds under trees, as trees are very competitive for both moisture and nutrients.
Forecasters are warning of more hot days to come. During heat waves, pot plants become stressed more quickly than plants in garden beds, and your pot plants may not getting as much water as you think.
If potting mix dries out, the first sign may be complete collapse of a plant. If you water dry potting mix in the normal way with a hose or watering can, your plants may not be getting as much water as you think. This is because potting mix shrinks slightly when it dries, leaving a narrow gap between the mix and the pot. When you water, most of it runs into the gap and out through the drainage holes, leaving the mix around the roots still dry. Seedling punnets and smaller pots can be thoroughly watered by immersing the entire pot in a bucket half filled with water, or use a laundry tub if a lot of pots need reviving.
Water should come over the top of the pot. Leave the pot in the water until bubbles cease to rise. Short term immersion won’t hurt the plants. Then lift the pot allowing it to drain into the bucket or tub. This method of watering also works very well when your water supply for plants is strictly limited.
For pots too large to be immersed in a container, fill some large soft drink or juice containers and insert 2 or 3 neck down into the potting mix. Provide support if necessary and allow them to empty slowly into the mix. Re-fill the bottles and repeat watering until water is being drawn into the mix very slowly. If heat is likely to continue for some time, place some mulch or stones on the surface of the potting mix to slow evaporation.
Potting mix can become incredibly hot when pots are in full sun. During extreme heat conditions move pot plants to a cooler spot, including under trees. Grouping them together helps retain humidity around the plants and reduces water loss through the leaves.
With some women it’s shoes or handbags, but with me it’s seeds, so I have to practice restraint when I go to Greenpatch Organic Seeds, as I did recently. Greenpatch supply a wide range of open-pollinated, organic seeds for vegetables, herbs, flowers, and grains, grasses and sprouts. You may have seen their seeds for sale at nurseries. Organic, open-pollinated seeds are not hybrids or GM seeds, and that means you will be able to save seeds from your crop for next season. Open-pollinated vegetable seed varieties are grown for flavour and vigour rather than shelf life.
Many of the seeds are produced at Greenpatch, but where cross-pollination can be a problem, other varieties are produced by local growers. I like buying organic seed that is produced in Australia because the seed comes from plants that have adapted to Australian soils and seasons. Previously, I had found that imported seed did not perform particularly well, and I achieved better results from seed I saved from those plants. We do save seeds from some of our crops but saving seed from all our vegetables and herbs can tie up garden beds for long periods while the seed matures, and being able to buy locally-produced seed makes life much easier.
Greenpatch also has a huge selection of fruiting plants, herbs, cottage garden and aquatic plants. Neville and Sophia have been producing seeds and plants on their farm for 20 years, and you can order seeds and plants by mail but, as Greenpatch is just off the freeway at Taree and only a short drive from our farm, I enjoy paying a visit and browsing through their stock for plants to add to our collection. You can see their catalogue at Greenpatch Organic Seeds.
If it appears to readers that I have been neglecting my blog lately, I apologise. My absence has been due to helping the Biological Farmers of Australia (BFA) prepare an organic gardening program for school children.
Although it is a very interesting project to be involved in, we have a deadline to meet, and it is currently taking up virtually all my time. I hope it won’t be too long before things get back to normal. In the meantime, please be patient. I will do my best to answer any gardening problems as quickly as possible.
Some parts of Australia have been enduring extremely hot weather recently and, apparently, there is more to come. Last summer, a period of intense heat caused scorching in many gardens.
To protect our vege patch this summer, we have been busy over the past few weeks putting up arches to support shadecloth canopies over our vegetable beds. Although European-based garden texts recommend full sun for most vegetables, where summers are hot and air pollution is low, full sun can result in sunscald. While Australian natives have evolved to restrict loss of water through leaves in hot, dry conditions, very hot plants, especially those that originated in cooler Northern Hemisphere regions – such as most of our vegetables and fruits, lose a lot of water through their leaves in an effort to keep cool.
Providing some light shade during the hottest part of the day can prevent sunscald and, by keeping the plants cooler, reduces their water consumption, an important consideration where water restrictions apply. Each canopy is positioned to allow morning sun to reach plants, yet not restrict air flow around them. Poor air flow (such as in fully enclosed areas) can produce conditions suitable for some fungal diseases to establish. Light shade can be provided by shade cloth or old netting curtains or sheets.
We use a lightweight, knitted green shadecloth, which probably gives about 30% shade, and has eyelets along the selvedge edges to make it easier to tie to the posts with strong garden twine. This allows us to adjust the canopy as the sun moves to its highest position around December 22nd (Summer Solstice), then moves northwards in the sky through January and February, our hottest months.
We have used ordinary wooden garden stakes to support the canopies. Due to the extremely strong winds this spring, we have had to drive the stakes deeper into the soil for stability – a process easier said than done at our place. We have shale subsoil, and the stakes tended to veer off at strange angles when hitting a lump of shale. No doubt star stakes would be easier to drive home vertically, but we have a roll of 38 mm plastic irrigation pipe that is the right diameter to slip over the ends of wooden garden stakes. Star stakes require a heavy-duty 51 mm polypipe for arches, or the 38 mm polypipe has to be lashed to the star stakes instead of slipping it over the ends.
Once the stakes are positioned, in pairs, 1.5-2 metres apart along beds, the pipe can be cut to size. The formula is half the width of the bed multiplied by ‘pi’, plus twice the length of the pipe to extend onto the stakes. But, cutting each piece of pipe one and a half times the width of the bed plus 70 cm, is a good rough guide for most garden beds.
I then measure the length the arches cover and cut the shadecloth to that length plus a quarter of a metre. I then turn in 11 cm of shadecloth each end and, using a doubled strand of strong fishing line and a bagging needles (although gardening twine is shown here for clarity*), I run a line of stitching across the shadecloth, 8.5 cm from the folded edge. Then we slip the end arches through this ‘hem’ to anchor the shadecloth. *The polypropylene tends to abrade garden twine during periods of very windy weather.
If neatness is very important to you, you can brace the end arches to eliminate any sagging in the shadecloth but, without the braces, it does the job and that’s the important thing. Although the shadecloth can be removed when no longer needed, the arches can be left in position permanently to support netting, when needed, or frost protection, if required.
There are other actions you can take to protect your garden in hot, dry conditions. See Heat wave first aid
As you can see from the last photo (taken as the shade cloth was being installed), the tomato plants have responded beautifully in just three weeks. Tip: if using wooden garden stakes, pay the little extra and buy the pointed ones. They are easier to keep straight when driving them into soil.
Occasionally, I receive e-mails from readers who are confused about which gardening or climate zone they live in. Australia has been divided into as many as eight different gardening zones because of the huge variations in temperature and rainfall across our continent. Altitude variations or geographical features within each zone will modify temperatures and rainfall patterns, breaking up the eight zones even further.
To complicate the issue, climate change is resulting in evolving milder winter conditions in some areas and longer, harsher winters in others. Last summer, extreme heat or rain events played havoc with a lot of gardens across Australia, and the extent of further changes related to extreme weather events is impossible for anyone to accurately predict.
However, Australia can be divided into three basic gardening or growing zones; Warm, Cool, and Temperate (as indicated in the diagram below). The zone divisions are based on the types of plants that will grow in a moderately irrigated garden in each zone
Within these basic zones, altitudes and geographical features gardens at higher altitudes will be cooler than those at sea level in adjoining areas. Sea breezes can provide a milder climate for coastal areas than those a few kilometres inland. Gardens where cold air can flow downwards will be less damaged by frost than gardens in valleys or where solid walls block the escape of cold air. These variations are known as local microclimates, and gardeners may have to make minor adjustments to what they can grow each month according to local conditions, and evolving microclimates brought about by climate change.
New Zealand has a more constant climate and can be divided into temperate and cool zones. Frosts do occur, and snow falls on the mountains, but New Zealand is not subject to hot winds from a parched inland. New Zealand is a very suitable place for growing an extensive range of species from Europe, North America, and the cooler parts of Asia.
WARM CLIMATE ZONES
These are frost free, or may experience some frosts in inland areas during their short winters, and are not suitable for plants that require a defined period of chilling. Warm zones are suited to warmth-loving Australian natives and plants, including fruits and vegetables, from warmer areas of the world. December, January, and February can be too hot for gardening in a lot of warm zones, and some warm zones experience distinct wet and dry periods requiring conventional vegetables and some annuals to be grown at different times to other zones.
The Tropic of Capricorn runs through the northern states of Australia from Rockhampton and Longreach in Queensland, just above Alice Springs in the Northern Territory, and crosses the West Australia coast between Carnarvon and Exmouth. In areas from Rockhampton northwards, tropical coastal conditions allow an entirely different style of gardening, while in drier areas high temperatures and lower water availability make gardening quite a challenge. Winter temperatures in areas within the Tropic of Capricorn can be higher than summer temperatures in some Cool Zones, and common vegetables from temperate areas can only be grown during winter months. Consequently, I have divided this zone into two sub-sections. Warm zones:
All of Queensland (except for the southern highlands),
North coast of NSW above Coffs Harbour,
Northern West Australia,
Northern South Australia.
COOL CLIMATE ZONES
These are areas where low temperatures occur for long periods. Frosts are common in winter and can continue into spring. Snow occurs in some areas. Cool zones are suitable areas for growing many European, Asian, and North American plants that require a period of winter chilling. Many of the fruits and vegetables we are familiar with come from cooler climates. They, and frost-hardy Australian natives, grow well in Australian cool zones, but frost-tender plants, and plants which require a long period of warmth to flower or fruit are unsuitable for these areas. Australian cool zones:
All of Tasmania, and the ACT,
Southernmost part of South Australia including Mt Gambier,
Around Albany in Western Australia,
Most of Victoria (except for Melbourne and Benalla areas),
Far south coast of NSW,
NSW tablelands and highlands. New Zealand cool zones:
The interior of the North Island,
The entire South Island.
(However, within these areas, protected local microclimates along the coast as far south as Christchurch can be regarded as cool temperate areas, extending the planting range.)
TEMPERATE CLIMATE ZONES
These, strictly speaking, are all areas on earth between the Polar Regions and the Tropics of Cancer and Capricorn. Although winter frosts occur in some temperate zones, soil warms quickly in spring. The areas of Australia not listed above can be considered temperate zones, because an extensive range of Australian and New Zealand natives, and decorative plants, vegetables, and fruits from temperate regions around the world can be grown in these areas. January to late February can be too hot for a lot of gardening activity in some Australian temperate zones, but mild autumn weather usually extends from March through May.
Minimum temperatures within metropolitan areas of Sydney, Adelaide and Perth are similar and tend to be slightly higher than those in surrounding areas. Melbourne’s minimum temperature is only slightly lower, and gardeners in Melbourne may find that they can grow many temperate climate plants in protected gardens.
On the North Island of New Zealand, North and South Auckland areas, Hamilton, most of the west coast to just above Wellington, the Bay of Plenty area, and the east coast to Hastings are temperate zones.