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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If you have any frost tender plants in the garden, I hope you've put them under cover as the weather forecast is for just 1 degree overnight.  Weather forecasts are imperfect, so if the temperatures are predicted to drop to 3 degrees or below I tend to cover tender crops as a precaution. 

Frosts generally occur when you have a clear sky, low temperatures and little wind. Tiny ice crystals form on the surface of the ground, your plants and other places like car windscreens. 

Plants that face the morning sun are particularly vulnerable as they defrost very quickly, breaking the plant's cell walls.  This can kill some plants used to growing in warmer parts of the world, turning them floppy and brown.  In larger plants leave the damaged leaves to protect the rest of the plant until later in spring: if you are lucky the plant may send out new shoots. 

But your best approach is prevention: grow cold-hardy plants outside at this time of year, or at least cover your vulnerable plants using one of the cold frames (or cloches) shown by Clare Jackson at a recent workshop, or some sort of frost cloth - old shower curtains or bubble wrap work well.   

Purple lilac is considered a good indicator plant: when the first green leaves appear on it, you can plant cool season crops suitable for spring conditions such as peas and beets.  And when the lilac is blossoming, there is  little risk of further frost so it is reasonably safe to plant summer crops such as beans and corn outside.  It will be interesting to see how this tradition holds up with the changing climate - our warmer than usual winter has had things flowering at some very odd times. 

There is more information about frost protection methods on the FAO site

Lilac - Indicator Plant

A lilac shrub on Cambridge Road in Hamilton has been flowering for over a week, while  lilac on Shakespeare Road in Cambridge has only just flowered. 

It is normally not considered warm enough to plant summer crops until after Labour Weekend (late October), but if you choose to use lilac flowering as a guide, you can plant fairly safely outside now.

NIWA's seasonal climate outlook for Oct-Dec 2012 is for average to above average temperatures: if the lilac is correct, above average temperatures are most likely.


Photo: Lilac flowers.

Daylight Saving time begins tonight: the clocks go forward one hour. This means more daylight in the evenings, which is excellent news for those of us who like to get out in the garden after work!

Here's the poem to we use to help remember which way to turn the clock:

In spring the clocks spring forward

In autumn the clocks fall back.

Green house made from recycled bottles

Thanks to Burton Worth for these photographs taken at a community garden in Wales. 

The bottoms were cut out of the bottles so they could be stacked into eachother.  Cambridge NZ Community Garden are hoping to make one similar.  It creates a warm microclimate.


This green house at Bright Smile (Community) Garden in Bella St, Thames, NZ is also made from mostly recycled materials.

CREATING WARMTH: a commercial tunnel house

Tunnel houses are usually an arched building covered in clear plastic, used to create a sheltered, warm environment.  Because they're covered in plastic, they are sometimes called polyhouses (as opposed to glass houses which are made of glass).

The tunnel house in the photo is being used to growing feijoa trees from cuttings. 

This is at Waimea Nurseries, near Nelson at the top of the South Island.  They grow about 15 different varieties of feijoas - NZ is the main feijoa breeder in the world, most are bred by Roy Hart, a NZ Tree Crops Association member.   

Waimea Nurseries produce nearly half a million fruit trees each year - apples, cherries, citrus, persimons, ...  They sell most of their trees to NZ garden centres (about 350 of them) and commercial growers.


Internationally, some tunnel house structures are made from bamboo, a renewable and often free resource.  There is a video some in India below - the sound is not good, but there are close ups of the way the structure is made about 1/3 through the video. 


CREATING WARMTH - more on Tunnel houses

Tunnel houses are also called hoophouses in some countries.

A step-by-step photographic guide to making a beautiful polytunnel from bamboo was created by Sunseed Desert Technology. 

When used in construction, bamboo needs to be protected from being wet or it will rot, so a concrete footing is often used.  It will usually last 2-5 years.

Sunseed Desert Technology also suggest you could use other types of cane or flexible woods, such hazel wood, which grows here. 

Hazel is very flexible when the wood is young - it is sometimes tied in a knot and left to grow for a few years, then harvested to use as a walking stick with a curved top. It also produces hazel nuts (the ones used in Nutella and the Ferrero Rocher chocolate treats)!

Photo: Bethy White's tunnel house, near Otorohanga.  It is full of subtropicals-that's galangal (a relative of ginger) coming out the door. 

The sliding door is recycled. You need a door at each end so that you can create a draft on hot days.

The white fabric around it is upside-down carpet (also recycled), which reflects light (good for plant growth) and acts as a mulch.  She also has the carpet under her washing line - it helps to dry her washing faster!

CREATING WARMTH - hoop cloche

Here in Hamilton a temporary cloche is used to protect a tender crop during early spring or late autumn. 


Make it:

A row of half hoops (can be made from recycled wire) is covered with heavy plastic - like a mini-tunnel house! 

Pin the edges with tent pegs or weight with something heavy - bricks or stones.

Leave the ends open for air-flow. 


Creating Warmth - Tunnel house pest prevention

At the Grandview Community Garden a group of volunteers from Hamilton City Council weeded and leveled the tunnel house floor last week. This will eliminate slug and snail habitat.

The tunnel house still needs a little work to finish it: if you are interested in helping please contact the WIC Community Garden Mentors, Clare 021 0387623 and Tim ph 021 2243109.


FREE BAMBOO (and bamboo shoots)

Hamilton City Council has stands of bamboo that they are willing for people to harvest: contact John Mills, Operations Manager, Parks & Open Spaces, Ph: (07)838 6625.

We also have a source of giant bamboo - contact me for Dion's details.  


Want to learn more about using bamboo or to share your knowledge?  There is a NZ Bamboo Society.



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