Last week of Horticulture Level 4

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Frost and fog at Bannockburn campus

This was my last week at Central Otago Polytech! Horticulture level 4 is complete. All that’s left to do is celebrate! And fill in this blog with the week’s activities.

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Practice knot using #8 high tensile wire

On Monday we had a tutorial on fencing. Trevor took us through the basics of lining up a site, positioning posts, wires and how tension and strainer posts work.

For the practical part we tried out some wire knots. The first one was the end post tie off knot (in photo above and diagram below).

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And the figure 8 knot to join two wires together.

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The next topic covered this week was frost. This completes the climate and weather modules. I really enjoyed this topic. Frost is one of the things that can majorly impact your crop with immediate results – and not in a good way! If something goes wrong with your frost fighting system or you misjudge the weather you could lose your whole crop in a few minutes.

Cromwell usually gets around 10 – 12 frost events during spring. This is when you need to have a system in place to protect all the fresh, vulnerable growth. Common methods are wind machines that draw down warmer air from the inversion layer above and overhead sprinklers that freeze water around the outside of a plant, creating latent heat that keeps the plant from freezing inside the ice layer.

Helicopters can also be used to push warmer air down from the inversion layer, but this would be a very expensive way to protect from frost on a regular basis.

Older methods of frost fighting include orchard heaters. Man, do these things put out some heat!

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It is a diesel burner that puts out an amazing amount of heat with the vents all open. You would have them closed during normal use. You need about 50 per hectare to keep the temperature up over the area. Although they aren’t expensive to buy, they do use a lot of fuel so could be expensive overall.

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Me – spur pruning the pinot noir

The rest of the week was spent pruning the last of the fruit trees at the Kawarau Gorge and working on some tools with Trevor in the workshop.

It’s been a great year and I’m so glad I did this course. I’ve learnt so much and am excited to put it to use in the real world. Now on with the job hunt!

Term 2 – Week 7 & 8 – Pruning

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Winter sunrise over Alexandra

At this time of year the major job going on across vineyards and orchards is pruning. It can mean some very chilly starts!

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Pruning the Bannockburn campus vineyard

Setting up the vines/trees for next seasons growth is essential for crop management and maximising yields.

In New Zealand grapevines are mainly spur pruned or cane pruned on a trellis system. There are so many different ways it can be done though.

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The main different between cane and spur pruning is that with cane pruning you are cutting off nearly all of last year’s growth and laying down two canes (shoots) to act as the arms of the vine. With spur pruning the arms (cordons) stay in place permanently and the shoots are cut back to new buds.

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Before spur pruning

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After spur pruning

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Close up of a gnarly spur

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Before cane pruning

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After cane pruning

There are advantages and disadvantages for both. Spur pruned vines can lose their fruitfulness over time; cane pruning doesn’t since you’re laying down young wood each year. Also, since cane pruning removes most of the old wood it removes disease and pest damaged wood. Spur pruning is a lot quicker and easier to teach, but you may need to spend more time and labour on canopy management later.

Only one more week to go!

Last two week’s weather:

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Term 2 – Week 6 – Soils & Fruit Tree Pruning

This week was split between soil science and fruit tree pruning.

Soil science delved further into soil creation (pedogenesis), looking at the influence of parent material, topography, climate, soil organisms and time. I won’t go too much into that except to say they all play a role in how a soil forms.

We also learnt more about cation exchange capacity of a soil and its water and nutrient holding capacity.

Clay particles and humus are negatively charged, attracting positively charged nutrients in the soil. They will be held in the soil and not leached out. The acidity of the soil (concentration of hydrogen ions) controls which nutrients will be forced off, back into solution in the soil.

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Clay will sometimes have a positive charge but phosphate will snag them all leaving sulphate and nitrate anions to be lost by leaching if not taken up by the plant right away.

In sandy soils the macro pores are too big to retain much water. It pretty much drains straight through taking nutrients with it. Clay and humus can improve the structure of the soil, providing more micro pores that hold onto water.

This is where the water holding capacity of the soil comes in. You only want to irrigate to field capacity – the point where the soil is holding as much water as it can without leaching.

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Nitrogen is the nutrient that is lost most easily from the soil. Aside from traditional fertilisers, nitrogen fixing plants can be helpful to add nitrogen to the soil. Plant roots and bacteria in the soil form a symbiotic relationship where the plant provides energy for the bacteria and the bacteria provide nitrogen to the plant. When that plant dies and breaks down in the soil other plants can then take up the nitrogen.

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We’ve come full circle now and are back to pruning – this week we’ve started pruning the fruit trees at Bannockburn Road. Pruning when trees are dormant means there will be a flush of new growth in spring. If you want to make a cut to a tree without encouraging growth you need to do it in summer.

Apricot trees are trained to grow in a vase shape, cutting back last seasons growth 2/3rds to an outside bud. This lets as much light into the centre of the tree as possible. Also taking out any diseased wood, branches growing in or crossed over.

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Pruning apricot trees – Karen and Praneel

Last week’s weather:

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Term 2 – Week 5 – Soil Science

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View of some terraces in the distance at Bannockburn, Kawarau River

This week we got stuck into soil science with Roger. There were several lectures and trips out and about to sample some different soil types. Surprisingly, this has been one of my favourite topics so far. I think that’s due to Roger’s wealth of knowledge about soils and horticulture.

So far we have covered the components that make up soil, soil development and horizons, structure, texture, nutrients and soil classification systems.

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Roger + spade = soil science

Soil is made up of organic matter, minerals, air and water. Organic matter provides nutrients for soil organisms and plants, gives the soil structure and increases the water holding capacity.

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The size of soil particles creates the soils texture. Sand is considered the largest particle, sandy soils are free draining and don’t retain water. Irrigation can be an issue. At the other end of scale is clay. Clay particles are tiny. There are micro pores between particles that hold onto water and nutrients making them unavailable to plants. Probably the easiest soil to manage is a mixture of all 3 types, sand, silt and clay. That’s called a loam soil.

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Texture triangle

This chart works out what sort of texture a soil has. If your soil has 60% sand and 10% clay it is a sandy loam. As you can see it doesn’t take much clay in the soil for it to be considered a clay. A 50% clay and 50% silt soil is still called “clay”.

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Different soil textures

Above are some photos from our outings to find different types of soil. At the top we have silt and clay soils.

Bottom left is an example of a gley soil. Organic matter sitting over the top of clay (O horizon over a C horizon). It has no drainage and is very water logged. This means the soil will be anaerobic, with none of the normal soil organisms to break down the organic material. Apparently a lot of the farmland in Canterbury was like this before the land was cultivated and drainage was sorted out.

Bottom right is an example of a semi-arid soil that has had irrigation. Semi-arid is probably the most common soil type in Central Otago. This soil develops where the climate is very dry. It’s low in organic matter (so lacking in nitrogen) and can have high salt accumulation since there has been little rain to wash it out.

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The nutrients a plant needs are broken down into macro and micro. Macro are nitrogen, phosphorus, potassium, sulphur, calcium, magnesium, carbon, hydrogen and oxygen. Micro nutrients are boron, chlorine, copper, iron, manganese, zinc and molybdenum. Basically, without all these in the right quantities the plant will have poor growth and poor fruit. In some cases too much can be just as much of an issue as too little.

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In this week’s propagation class we did lily scaling – the process of dividing lily bulbs to end up with more plants. They are dormant for winter now so can handle being dug up and broken to bits. You just snap the scales off at the base and pop them in a plastic bag with damp vermiculite. They get stored on the heat bed. You could do this at home using the airing cupboard. Here’s what the flowers look like:

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Lily regale

We also dug up some of the peonies and divided them as well. They are quite freaky looking! It’s hard to know where to start.

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Peony tubers ready to be divided

The flowers are gorgeous in the summer though, so it’s worth it. Here’s a photo of the peony garden I took at the end of last year:

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Last week’s weather – a lot of minus temps in the minimum columns!

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Term 2 – Week 4 – Organic Certification

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Burn Cottage Vineyard – biodynamic

This week we learnt about going through the organic certification process. There are a few different ways to go about it. Either through Bio-grow, Asure Quality or Demeter. The first two are organic certification only, Demeter is for biodynamic properties. Biodynamic is a different philosophy from organic but even more strict on inputs.

The organic certification process takes 3 years to complete. There are audits each year to ensure all criteria are being met – these carry on for the whole time a property is registered as organic.

We went to Burn Cottage Vineyard in Cromwell (I’ve had their Moonlight Race Pinot Noir before and it’s really nice) which is run bio-dynamically. They make their own compost from organic materials, have their own livestock on adjacent fields, use under-vine weeders for weed control, metal poles as opposed to tanalised wood, have other crops and areas planted with different species and use many other practices that make up the biodynamic system. They feel that all these things make a real contribution to the health of the vineyard and in turn the quality of the wine.

Some parts of biodynamics don’t make sense to me, but organic practices certainly do. It seems to me that if managed properly crops can be just as good as conventional growing, better for consumers, better for workers on the property and far better for the environment. I guess the only negatives are that it takes more planning and time to execute so more labour costs, i.e. hand weeding vs. spraying with herbicide.

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April collecting wood from a cherry tree for grafting

We also started collecting some wood for grafting. The wood is dormant now so can be collected and stored until next spring when it will grafted onto rootstock. It is important to take dormant wood so that when you graft it onto active rootstock in spring the graft union will have time to form. Otherwise the union would not form (callus) quickly enough to supply water or nutrients to the scion. It takes about 7 – 10 days for this to happen.

The dormant scion wood gets wrapped up in soaking wet newspaper, put in a plastic bags and stored in a fridge or cool-store.

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Propagation update – lots is happening in the potting shed and glasshouses. The Clematis marata seed I planted a few weeks ago has germinated and I have 3 seedlings! It doesn’t sound like much, but the seed was really old so I wasn’t sure if I would get anything.

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Clematis marata seedling

The kowhai we sowed last November were ready to be re-potted into 10cm pots.

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We also did some deciduous hardwood cuttings. I did Vitis ‘July Muscat’, a table grape. Hardwood cuttings are much longer than the other cuttings I have done (softwood, semi-softwood or herbaceous). They need all that energy stored in the stem. These are have gone into 10cm pots of wet perlite. You could leave them outside over winter but we’ve put these on the heat bed to get some roots going a bit more quickly.

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Weather wise, it’s feeling a lot more wintry now. Lots of trees with no leaves and mornings switching between either crisp frost or heavy fog. Some vineyards have already started pruning.

Last week’s weather:

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Term 2 – Week 3 – Weather

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Snow that fell over the weekend

This week we learnt how to read weather maps and come up with our own forecasts. It was quite timely since we were due to get the first snow of the year that weekend – and yes we sure did get snow!

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Example of a weather map for the South Island

Some good websites for weather forecasts are MetService or MetVuw.

The maps show areas of high pressure or low pressure. The lines on a weather map are isobars that connect areas of equal pressure. When isobars are close together it means there will be strong wind.

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High pressure (over 1000 hPa) means weather will generally be calmer and will have clear skies. The higher the pressure number the slower the system will be moving. The wind will travel anticlockwise around a high (clockwise in the Northern Hemisphere). A ridge is a section of higher pressure extending from a high pressure system. Ridges give better than expected conditions. Highs move towards lows and will look like they are following them across the map. In summer weather should be sunny and warm and winter will be cool and frosty.

Low pressure is where all the drama happens. Clouds, rain, cyclones (940 hPa), hurricanes (800 hPa) and tornadoes (500 hPa). Air (filled with water vapour) is rising and expanding, when it reaches the dew point the water vapour condenses, forming clouds. Lows move clockwise. A trough is a section of lower pressure extending from the low, bringing worse than expected weather.

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Types of clouds

There are so many different types of clouds. The lowest being fog and highest are cirrus. Cirrus are the very high looking, wispy clouds. They can indicate that a change in the weather is coming in the next 24 hours.

Cumulonimbus clouds are massive clouds that go right up to the top of the troposphere. They can bring hail, lightning, tornadoes and flash flooding. They form when there has been strong heating at ground surface or from a cold front slamming into warmer air.

Fronts are a boundary between warmer and cooler air. They don’t like to mix and cause trouble in the form of clouds and rain.

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Although a warm front sounds like it would be nice, it’s not! All fronts bring worse weather. Stationary fronts can cause lots of rain and flooding. Yuck!

I’m crossing my fingers for lots more high pressure systems coming my way, although if I can’t have that, I will take the snow 🙂

Last week’s weather:

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Term 2 – Week 1 & 2 – Plant Science

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The first two weeks of term 2 have been focused on Plant Science (botany). It is essential to have knowledge around the basic structure of plants and the processes within plants (like photosynthesis) to help understand some practical things, such as grafting, wilting plants, pollination, seed production and pruning.

We started off going right back to basics and looking at the smallest part of plants – cells!

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Plant cells are a bit different to human or animals cells but share many of the same features; nucleus containing hereditary material and mitochondria as the power house of the cell. Plant cells have a cell wall that covers the cell with cellulose that is semi-permeable allowing the movement of dissolved minerals. They also have a vacuole that holds water and minerals in a membrane that is separate from the cytoplasm and supports the shape of the cell.

We also covered stems, leaves, roots and flowers.

Stems and roots have areas called meristems, which is where cells divide and the plant grows. Meristems are found in the tips of shoots and roots (apical meristem) and around the outside of a trunk or branch (lateral meristem or vascular cambium). When you are grafting two plants together it is the vascular cambium regions that need to be joined for a connection to be made.

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Cross section of a woody dicotyledon stem

The stem also contains the xylem and phloem. The xylem moves water and minerals from the roots up throughout the plant. The phloem moves sugars and nutrients made by photosynthesis and respiration down throughout the plant.

Roots help stabilise the plant, take up water and dissolved minerals and nutrients from the soil and can also act as storage tissue for energy for the plant. Rhizomes, bulbs, corms and tubers are examples of storage tissues.

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Leaves are the main part of the plant where photosynthesis happens. There are tiny pores (called stomata), usually on the underside of the leaf, that open and close to allow gas exchange. The veins you can sometimes see on a leaf if you look closely, are made up of vascular bundles that consist of xylem and phloem cells.

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Flowers are the seed bearing part of a plant. They are where pollination happens and fruit forms.

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Plants can have flowers that are “complete”, meaning the flower has both male and female parts (roses, plums); monoecious, separate male and female flowers on the same plant (pumpkins, zucchini) or dioecious, separate male and female plants (kiwifruit, ginkgo). This affects how the plant pollinates, either self pollinating or cross pollinating.

There is a lot more involved in plant science, this is just a few basics that barely scratch the surface. I find diagrams make it easier understand and to get my head around all of the terminology.

Last couple of week’s weather – winter is on the way:

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Term 1 – Week 9 – Last week of term

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Early morning at McArthur Ridge vineyard

Term one is over! Actually it’s term 3 for me since I started half way through last year. I finished off my pests and diseases assignments and successfully did my plant ID test.

We harvested the chardonnay and pinot noir grapes at the Bannockburn campus. It was exciting to see them going off to be turned into wine. The vines look so bare now, no fruit and the leaves are falling off now as well.

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Chardonnay grapes

In propagation we processed some Pittosporum tenuifolium seed. Little pods hold lots of sticky seeds. Once you manage to get the seeds out you rub them with fine sand to separate them.

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Left: seeds in pods. Right: Pittosporum young tree and seeds rubbed in sand.

Over the holidays I worked at McArthur Ridge vineyard, helping with the harvest. It was a really great experience. Long days and hard work but very rewarding and such a beautiful setting. It’s such a huge operation (170 hectares of pinot noir) so it was interesting to see how it was all organised.

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Pinot noir ready to be picked

Last week’s weather:

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Term 1 – Week 8 – Tractors, Quads & Cuttings

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Dylan practicing on the John Deere

The majority of this week was focused on gaining skills on the tractors and quad bikes. We learnt how to check and clean the PTO connections and hook up implements to the tractors. I looked like a mechanic by the end of the day – grease and oil everywhere!

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PTO that hooks up implements to the tractor

I can now take the buckets off and on the John Deere and Claas tractors, use the tractors to tow a sprayer (2,000 litres) and mower. The sprayer is 5 metres long so I was a bit nervous about turning at the end of the rows. Luckily I didn’t take out any trees…

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Tractor and sprayer in action

On the quad bikes we practiced reversing with the trailers. That was a real challenge for me. By the end of the week I had improved a lot but it doesn’t come naturally to me.

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In propagation class we did a lot of cuttings. I went off and collected the material for my cuttings, Hebe ‘Autumn Glory’. It’s a really nice shrub that has purple flowers. Back in the potting shed I trimmed them up, cutting the stem just under a node, cut the lower leaves and all flowers off, dipped in #2 hormone and popped them into a tray with 50% potting mix and 50% pumice. Hopefully they will have a good strike rate.

At this time of year most cuttings would probably be considered semi-hardwood. The new growth from summer has started to harden off but tips might still be a bit soft.

After that I helped Karen re-pot the cuttings she had done previously that have now rooted. There was a pretty good success rate, only about 10 of the cuttings didn’t have new roots. We re-potted them into 10cm pots with standard potting mix.

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Re-potting cuttings that have rooted

I checked up on the cuttings I had done last week (Heliohebe hulkeana) and all of them have rooted except for one. Pretty happy with that result!

Last week’s weather:

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Term 1 – Week 7 – Alternative crops & Seed sowing

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Bridge over the Clyde river in Alexandra

The main crops currently grown in Central Otago are grapes/wine, cherries, apples and summer fruit. This week we looked into alternative crops for Central Otago; crops that will grow well here, will potentially have a market and can be grown on a smaller scale than traditional crops.

Some ideas are: berries, olives, saffron, strawberries (maybe hydroponic), walnuts and peonies.

Saffron (Crocus sativa) is an autumn flowering crop so it could fill a gap for some growers after their main summer harvest. The corms start sprouting in April with the flowers coming shortly after. Flowers need to be picked before they open, then the stamens are removed and dried. The plants then continue to grow throughout winter and are dormant over spring and summer.

Saffron is the most expensive spice in the world so there can be high returns – 1kg = $20,000 – but you need so many flowers to get the quantities needed. It takes 150,000 flowers to get 1kg of saffron. Corms can be lifted and divided about every 3 years.

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Branch tied down for better positioning

There was another session on tree training for the young cherry trees. This time on the central leader style – one main vertical trunk with several layers of near horizontal branches at right angles. String is used to tie down the branches into the right positions. This needs to be done while the trees are still young and supple enough to be manipulated.

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Jeanine with her finished tree

In propagation this week we spent some more time on seeds and dormancy treatments to start germination.

  1. Stratification – treating seeds with moisture, cold for a certain number of weeks. Usually need for plants that come from a cold climate.
  2. Scarification – rub with sandpaper to break the seed coat allowing moisture to imbibe.
  3. After ripening – warm dry storage after collection

I found it interesting that some seeds need total darkness to germinate, like cyclamens.

To sow the seeds we used a ‘seed raising mix’ made up of 50% potting mix and 50% sand. The sand allows a lot of oxygen to circulate around the seed. You don’t want the seeds to get too wet. Spread the seeds out and cover with vermiculite to twice the diameter of the seed. You could use a thin layer of potting mix instead.

Damping off is a fungal disease that causes problems for seeds and seedlings. It causes mushy spots on seedlings and withering at the base of the stem. Seedlings will collapse and die. Damping off can be prevented by not over watering seeds, using new uncontaminated potting mix and by cleaning seed trays in a chlorine solution.

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Collected seed ready for sowing

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Clematis marata collected from Mt Rosa – old seed so I sowed the lot

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Greenhouse 1 is full of freshly sowed seeds

On Friday we had the Central Campus Plant and Food Fair. It was a really fun day. Lots of plants were bought (one couple spent $800 just on lavender plants!) and the food put on by the cookery students was delicious.

Last week’s weather:

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