Weather is about the wind, rain, sunniness and temperature of a particular time. It is one of Kiwi's favourite topics of conversation, and even more so amongst gardeners! Our uneven terrain makes weather prediction difficult, but you can find weather forecasts at the Metservice for Hamilton and Tokoroa, or at the end of television or radio news broadcasts. 

Climate is the average weather for a particular place over a long time (eg 30 years).  NIWA is a government owned agency that tracks and predicts our climate - useful for planning planting. 

Plants from different parts of the world have developed in a particular climate.  When we bring them to the Waikato, their survival depends largely on how closely we can match their climate of origin. 

Another other key factor is soil, which feeds the plant. 

New Zealand has four seasons:

  • Spring - September, October, November
  • Summer - December, January, February
  • Autumn - March, April, May
  • Winter - June, July, August
In the Waikato our prevailing (most common) wind comes tends to come from the West. Southerly winds tend to be cold and like south-westerlies tend to bring showers and sometimes rain and thunder.  (Very occasionally we get tornadoes but they are generally small.)  Sometimes tropical depressions move down over New Zealand, particularly during December and April, bringing some of our worst storms.  They can bring heavy rain and wind. 

There is a reason that the Waikato is "where the grass is greener": we tend to get rain all year round, which why we have so much horticulture and dairying in this area.  More rain falls in winter than summer, with Hamilton's average rainfall about 1,200 mm per year. Our climate is also fairly humid which can make fungal diseases a problem. We are known for our fog.  Fog  forms over moist or marshy ground (such as drained peat swamps) on cloudless nights with light winds, so are particularly common in Autumn.  Climate change is expected to not only increase our average temperature, but generate more extreme weather events such as droughts and floods.

Here in the Southern Hemisphere, the warmest part of your garden faces North: it will get the most sunshine. Hamilton averages about 2013 hours of sunshine per year.  Most food plants do best with 6-8 hours of full sunshine per day.  In the tropics the daytime length (ie period when the sun is in the sky) is pretty constant, but here the day length varies considerably.  Our winter solstice (the longest night/the shortest day), falls on the 21 June, when the sun rises about 7:30 am and sets about 5:10 pm, while the summer solstice (longest day of the year) falls around December 22, with the sun rising about 6 am and setting about 8:40 pm.  The equinox (when the night and day length are the same), falls in March and September: this is often a period of windy unsettled weather that can damage plants if they are not sheltered.  Some gardeners believe that the shortening days after the summer solstice trigger many plants to go to seed (start forming seed).

The coldest months of the year are usually July and August and the hottest months in January and February.  In Hamilton, the average maximum temperature in January was 24 degrees compared with July's 13.6 degrees.  The average January minimum temperature is 12.7 degrees, compared with 3.8 degrees in July.  Temperatures have been recorded as low as -9.9 degrees and as high as 34.7 degrees.  Hamilton gets an average of 64 frosts at ground level per year. (Information from the Metservice)  Generally the worst of the frosts are over by Labour Weekend in October. 

A private weather station in Tokoroa keeps some historical temperature averages.  In the years 2008-2010 Tokoroa averaged 52 frosts per year.  The average January maximum temperature in this period was 30.7 degrees, compared with 15.3 in July.  The average January minimum temperature was just 4.3 degrees, compared with -6.0 degrees in July.  Only December - March were frost free.  

 

Tokoroa is at an altitude of 326 meters, much higher than Ruakura in Hamilton at just 40 meters, and further south.  These are factors in Tokoroa having colder temperatures.  Snow is extremely rare in Hamilton, but less so in Tokoroa. 

 

Hamilton has varied terrain and varied soil types with it.  There is a soil map here.  Click on the area where you plan to garden and click to see the soil type, for example gravelly sand, clay, silt loam and peat for example.  Each type has its benefits and downsides, suiting different types of plants.  Tokoroa has predominantly volcanic pumice soils over volcanic ash and are often low in the trace element cobalt. 

 

Within your garden there may be many micro-climates - areas that are more windy, cooler, or wetter than others. There can also be variations in soil type. The observant gardener matches plants to the different areas, and creates new micro-climates using techniques like cold frames or changes the soil with the use of 'soil amendments' such as compost.

 

If you have any questions, information or suggestions about weather, climate or soil, please add them to the discussion.

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Climate Outlook for February - April 2012

NIWA has published its next seasonal outlook at: http://www.niwa.co.nz/seasonal-climate-outlook-february-april-2012

The moderate La Niña weather pattern that has given us a slightly wetter summer is likely to continue into early autumn (March), then fading out.

Autumn temperatures for the Waikato region are likely to be near average - so around 16.4 - 17.0 degrees Celcius. 

Seasonal rainfall totals, soil moisture levels, and river flows are all likely to be near normal.  This means about 194 - 272 mm of total rainfall.

In our part of the Pacific region, January to March is the peak cyclone season. Generally at least one ex-tropical cyclone passes within 500km of New Zealand in 9 out of 10 cyclone seasons. 

Photo: I associate autumn with lots of foggy mornings followed by clear blue skies.  The herb in the foreground is fennel which has an aniseed flavour that goes well with fish.  The flowers taste just like black jelly bean sweets, but without the loads of calories!

Autumn is definitely here, with shorter daylight hours, cold nights and warm sunny days. The trees that lose their leaves in winter (ie deciduous) are turning beautiful colours.

Being active is a great way to stay warm!

Some plants love this weather - Clare recommends sowing celery, spinach, pak choi, spring onions, cabbage, carrots, silverbeet, broccoli, parsley and peas during April.  

 

Autumn Leaves

Many trees from colder countries in the Northern Hemisphere go into a kind of sleep over winter called dormancy.  When the weather starts to get cold they drop their leaves.  These trees are called deciduous. Most NZ native trees are the opposite -called evergreen (ie always green).

 

The best way to stay warm in the garden (apart from putting on warm clothes!) is through aerobic exercise – movement that makes your heart and lungs work!  In Autumn and early winter briskly raking dead leaves off the lawn and sweeping the leaves off your deck and paths is great aerobic exercise.  Wet leaves get very slippery and can make wooden decks rot, so it is good to sweep them up. 

 

You can use the leaves as a mulch or compost them. They are high in carbon.  You could stock-pile them in bags next to your compost bin to add to the mix over the coming year.  At Locovore, a market garden, they fill a garden bag with leaves at this time of year to make a type of compost called leaf mold. Put the leaves in a black rubbish bag (black absorbs heat). Do not to squash them down. Stir occasionally if you remember.  After about 4-12 months you will have compost with no weed seeds: good mixed with some sand to use in seed raising trays.   

 

Photo: Left - Outdoor broom for sweeping leaves off decks and paths.  Right: Rake - this one is adjustable - you can make the gaps between the tines (like fingers) bigger or smaller.

FROST

Frost forms when the temperature drops to 0 degrees Celsius or below, causing ice crystals to form. It makes your lawn crunchy and the garden white. ‘Tender’ plants are killed by this, so if you are growing tender plants, check the weather forecasts for temperatures below 3 degrees from autumn through to spring. 

Frosts are more likely when the weather is fine and there is little or no wind.  They usually happen in the very early hours of the morning.

A ‘light frost’ is where temperatures drop no more than -3 degrees Celsius.  Any lower than this is described as a ‘hard frost’.  Plants that can survive a light frost but not a hard frost are described as ‘half hardy’.  Plants that can survive hard frosts are described as ‘hardy’.

The easiest way to garden in winter is to grow only hardy plants—this is what the kitchen garden at Hamilton Gardens does.

Some trees are tender when they are young, but become hardy as they mature.  For example, protect your young citrus trees from frosts for at least 3 years.

The most common way of protecting your tender plants from frost is by covering them with a lightweight cloth overnight.  Recycled bubble wrap or old shower curtains will work.  Your plants need light, air and water, so uncover them during the day.

Photo: Ice out of a pet's water bowl on a frosty fence. The temperature had dropped to about -3 degrees Celsius. (Courtesy Bruce Mercer)

Spring does not mean the end of frosts:  the Hamilton weather forecast is for frosts for the next few days, so keep your frost tender plants covered at night. 

Photo: frost on sprouting broccoli. 

Broccoli is a brassica, and like most (all?) of this family it is frost hardy - it is not damaged by frost.

Spring is nearly here...

At this time of year, many of us wonder why we have chosen to live in such a cold rainy place!  A walk around a garden in a sunny moment between showers may cheer you up: the stonefruit trees (plum, peach, almond, etc) are either blooming (flowering) or about to flower. 

Some of the deciduous plants (the one that dropped their leaves over winter) like currants are starting to show new leaves.  The raindrops hanging from the branches sparkle in the sunlight.  The bright yellow flowers on my bok choy are feeding insects and promise seed for next season's crop. I have more tui (a native bird) visiting - they look and sound beautiful.

Spring officially starts on 1 September.

 

Photos:

Top: Black currant leaves opening

Middle: Almond blossom

Bottom: Plum blossom.

The Benefits of Compost

Composting is not just good for your garden and your budget (reduced rubbish bag costs), but the planet as well! 

Organic waste is a problem in landfill (rubbish tips) as it produces methane, which is a greenhouse gas.  Greenhouse gases contribute to global warming and rising sea levels.  Transporting organics to landfill also increases carbon use, and landfills reach their capacity sooner.  

Hamilton City Council has started an Organic Feasibility Study to see how the city can reduce the amount of organic waste going into landfill, particularly from businesses.

Composting helps to put carbon into the soil, rather than into the air.  So if you are composting: well done!

CALCIUM (Ca)

Calcium is a fertiliser: all plants need some calcium to be healthy - and so do we!

Soils in limestone country may already be high in calcium - there are areas of limestone around Raglan and Te Kuiti, for example.  Farmland is often high in calcium.

Organic sources of calcium include:

  • dolomite lime
  • gypsum (calcium sulphate)
  • calcite (calcium carbonate) - limestone - formed from ancient shells
  • ground shells (eg ground oyster shell, also called oyster meal)
  • ash from untreated wood (also includes potassium (K), important for forming fruit)
  • dried, ground egg shells – eg put shells in oven after you have finished baking, switch oven off and leave to dry overnight.  Use a mortar & pestle, or food processor to grind them up
  • Bone meal, or Blood and Bone - sold as a powder made from animal bones, also contains nitrogen (N) and phosphorus (P).

If you want to make your own shell or bone meal, try burning the shells or bones first.  

Use these sources of calcium sparingly: more is not always better!  Perhaps the best way of adding calcium to your soil is via your compost - sprinkle a little through the layers.

If you do add calcium directly to your soil, mix it into the soil before planting. 

Adding calcium to soil is sometimes called 'sweetening' the soil. 

Shells, ash and bones are renewable sources of calcium - and can cost you nothing.

If you are a science geek (I know there are a few of you out there!) you can read more about calcium, including its relationship with pH here.

Tip: Many of the fertilisers you buy in the shop list the amount of "NPK" = the chemistry symbols for nitrogen (N), phosphorus (P) and potassium (K).  These are some of the important minerals needed by plants - but there are many more that plants need, such as calcium and magnesium.

Photo: Grinding dry egg shells in a mortar and pestle.  Tomatoes often benefit from a tsp of this mixed into the soil when you transplant them.

Peat Soil

The Waikato has about 94,000 hectares of peat lands - about half of all the peatlands in NZ.  In places the peat is 18 metres deep!  Peat forms in wetlands (also called bogs or swamps) and is made from partly decomposed plants (see photo, below).  Peat is very slow to form - here, our peat took over 18,000 years to develop, so even though peat is organic, it is generally viewed as a non-renewable resource.

Another reason for conserving peat is that it is mostly carbon, as it is cultivated and/or dries out it releases carbon dioxide  into the atmosphere, contributing to global warming. (Learn more about Waikato peat bogs here.)  Much of our peat wetlands have been drained.

Peat is naturally anaerobic (has no oxygen present) and is very acid (soil pH <4.5).  Draining and cultivating peat soil makes it shrink - I had friends living in a house on peat soil near Waikato Hospital: the house moved as the peat shrank, making the doors and window stick.

Peat is flamable, and can even burn underground.  Peat fires used to be common in the Waikato - another good reason not to smoke!  Waikato is famous for being foggy, but as more and more of our wetlands have been drained, and the number of peat fires have reduced, we are getting less and less fog.  You can read more about Waikato's landsape, soils and climate on Te Ara - the Encyclopedia of New Zealand.

Peat was a traditional ingredient in store-bought potting mixes, but it is increasingly being replaced with (renewable) coconut fibre (coir).  If you are making your own potting mix, you can replace the peat with leaf mold (rotted leaves), rotted sawdust or a mixture of these.

Plants that come from boggy areas like peat soils, including blueberriescranberries and Camellia sinensis - the plant used to make tea.

Photo: Peat soil, blueberry orchard, Monovale, south east of Hamilton.

Fireworks, Fires and Fertilisers
You will have noticed lots of fireworks going off this week: we are celebrating Guy Fawkes (5 November), an event that has its roots in English history. This event has traditionally also been celebrated with bonfires: people sometimes bake potatoes or toast marshmallows (a type of sweet) in the fire. The word 'bonfire' came from the words 'bone fire'.
November in the northern hemisphere is autumn, and it was common to kill some of the animals that had been fattened up over the summer, preserving the meat for winter when there would be little for the animals to eat. The bones would be burned with (untreated) wood and the ashes used as garden fertiliser. Bones are a renewable source of the mineral phosphorous (P) and wood ash contains potassium (K). Both minerals are essential in small amounts for healthy plants. You can learn more about some renewable home-made fertilisers here.
Some NZ local Councils ban bonfires in towns and cities all year round. Most (perhaps all) Councils ban bonfires over summer when plants are dry and the risk of them spreading is too great. Fire bans are advertised on the radio, local newspapers, etc. During a 'restricted fire season', you will need a permit from the Council - this can take around a week to arrange, so plan ahead. An 'open fire season' means you can have a bonfire and don't need a permit.
Remember: If you are on peat soil, do not have a fire where it can touch the ground - peat burns! If you are not sure if your property is on peat soil, contact your local council and they can tell you - this service is free.
You do not need a fire permit if you use an incinerator, pizza oven, BBQ or cooking fire: you can use these all year around. Even an incinerator made from a large metal drum with an air hole cut out of the bottom will help the fire burn with less smoke than a bonfire. Here's instructions for a DIY incinerator that can also be used as a patio heater. It is made from recycled materials.
Warn your neighbours when you plan to have a fire (including smoking fish etc) - otherwise they may think your house is burning down and dial 111 to get the Fire Brigade to rescue you. You may also be able to arrange to have the fire when they are out. Some councils will fine you if you create lots of smoke that annoys your neighbours - so don't burn green (fresh) garden waste. Do not burn plastics, tyres, etc: these contain toxic chemicals. The best time of day to have a fire is in the early morning when there is little wind: the smoke will go straight up without bothering your neighbours.
Don't set up your fire under a tree. Always make sure you have water or some other way of putting out the fire close by. There are some good tips here. If you have any questions about fires contact your local Council or the local Fire Service Safety Officer.

Tim’s tips on how to be water wise in your garden:

  • Minimise the amount of water you need to use: in the Waikato we have a good year round rainfall so it’s quite possible to water only at the time of planting. Incorporating large amounts of rotted organic matter in the soils at time of planting and mulching plants as they grow means that your garden beds act as water storage, saving a lot of time and money. Digging a large planting hole and filling with rotted mulch or good compost will save time in the long run and help ensure a good crop.
  • With well prepared and mulched top soil plants should be able to draw water from surrounding soil to get them though dry spells of one or two weeks. If you do have to water then a good soaking in the evening once a week will replenish the soil “stores”.
  • Choose plants that don't need lots of water
  • Contour your garden to make the most of your water, and plant thirstier plants such as potatoes lower down the slope or deeper where they will naturally get more water.
  • Collect and store rainwater for your garden if this is practical. Remember in the home garden the best place to store water is in the soil.

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