The Shade Tunnel for Leafy Greens

 

So much of what is written about growing leafy greens, salad and dainty herbs is written for the temperate and sub-tropical climates typically found in Southern Qld, NSW and Victoria. In the temperate areas, salad vegetables are grown outdoors, in full sun, in the summer. In sub-tropical areas, salad vegetables grow well with a little protection from taller growing vegetables and will grow well into autumn. Seed packets state that their contents will gladly grow in full sun.

 

Perhaps the single biggest obstacle for the tropical gardener comes from that first experience when they busily follow the instructions on the seed packet and sow away happily only to have their efforts mostly destroyed that evening by torrential rain which rips away the top layer of soil, carrying delicate seeds with it. What does survive may sprout but the sun wilts and withers the young seedlings and perhaps a lone survivor might make it to a stage where the grasshoppers defoliate it in a matter of hours. What’s more, this is what happens in winter! Imagine summer when the conditions become twice as extreme.

 

One solution is to grow tropical leafy greens which show a considerable resistance to the onslaught of tropical conditions. Abika, Ceylon Spinach, Sissoo, Mushroom Plant and much more. You can read about them here.

 

I love these tropical greens and they certainly provide a much needed boost to the diet in the wetter months however, I couldn’t go without my lush leafy greens, dainty herbs and salad leaves. Lettuces, rocket, parsley, spinach, silver beet, and brassicas – the list goes on. All those traditional vegetables.

 

As most do, I failed in my first attempts to grow these cooler climate greens and began to question if it was even possible. There seemed to be so many challenges but I was determined to rethink the old knowledge and ignore the instructions on the seed packet.

 

First of all, the concept of growing leafy vegetables in full sun is a concept for cooler climates. Even morning sun, half day sun or dapple light is too much for the delicate leafy greens. A ray of tropical sun will burn a hole in a lettuce leaf, even if it is only on it for a moment. If you grow the vegetables under trees, the delicate salad leaves are destroyed by the copious amount of twigs, debris, leaves and branches that are knocked down in solid rain. Even solid rain will destroy plants.

 

Shade cloth is the best alternative as it gives the plants protection from both sun and falling debris. It also softens the impact of heavy rain. I decided upon 50% shade cloth that would be pulled tight over a structure. The structure would be in full sun and over the day would allow enough light through to grow healthy happy plants.

 

Leafy greens need to be loved, nurtured and molly coddled to grow into fat juicy delicious greens. Intermittent watering, harsh sun, insect attack and other stressors will lead to tough and bitter greens. The shade cloth will protect the plants but also keep the bugs out, another bonus. Combined with a good watering system and rich soil, I should be pushing up these greens most of the year.

 

The structure itself is very simple and affordable to build. You can find the plans and other uses for this design here.

 

Once the basic structure is built all you need is to install a simple watering system. The ceiling bats used have a groove down the centre which is perfect for a length of poly pipe. I attached to this two overhead sprinklers and ran the connection to a nearby tap. I could water as much or as little as I liked. I also had a large amount of corregated iron hanging around which I used to build up garden beds on the interior and the exterior of the structure. My intention was to have the leafy greens inside and the outside beds were to be used for vegetables that love the sun.

 

As I was starting this project in spring, I knew the wet season was looming but I saw that as an opportunity to experiment with what I could grow. My garden beds are about 50cm high and I chose to fill them with a soil product we know locally as “mill mud”, a by-product from the local sugar mill. You could fill your beds with any garden mix, compost or even a no dig style of garden. As long as what you choose is rich, well drained and ideally, free from weed seeds.

 

Keep the shade tunnel moist. A light misting periodically throughout the day will help to keep the temperature down. Damp shade cloth acts like an air conditioner as the external breezes hit it. I tap timer could give you short burst of misting throughout the day.

 

I started out with seedlings of all sorts. I chose loose leaf lettuces with heat tolerance, mitzuna, kalian, tatsoi, Chinese celery, chicory, rocket, radishes, beetroot, Choy sum, silver beat and a few other sorts. I took the time to propagate the seeds in trays and then planted them into the garden beds. The radishes and rocket were planted in as seeds. Radishes are fast growing and within four weeks we were making salads of radishes mixed with baby leaves of all sorts. Everything flourished, well into the summer heat. By Christmas, we were enjoying a huge amount of lovely fresh greens and my guesst were amazed that my lettuces in the shade house had not bolted to seed. By mid January, the heat and humidity was really ramping up and I noticed that some of the more tender brassicas began to fail. They seemed to suffer from some sort of rot bought about by the humidity but a few days after that I was confronted with a caterpillar plague of biblical proportions. Everything had been munched!

It was certainly a lesson learnt in the need to keep the door closed and excluded those lovely butterflies and their eggs. The chooks ate well over the next few days as I ripped up all the damaged veg and caterpillars. I was determined to carry on.

 

As the summer got hotter and wetter, I reseeded the beds with rocket, mitzuna and basil. Usually I would grow basil without much protection but the grasshoppers have been particularly bad this year. Mint, another victim of grasshoppers was also moved into the shade tunnel. The patch of chicory and Italian Parsley (the caterpillars did not touch these) powered on. I did try a packet of lettuce seeds but the germination rate was very low. Lettuce finds it hard to germinate over 30 degrees Celsius.

 

Weeds are something that will always need to be kept in check and my shade tunnel was no different but I find it very easy to whip around and pull out any weeds once a week.

 

It is now March and as I start to consider the cooler weather that will be upon us soon, my shade tunnel is doing very well. I plan to plant out my “winter” leafy greens in April and will be growing broccoli, lettuce, spinach and more but until then, I have large amounts of goodness to eat.

 

The top lessons learnt were to make sure your design is bug proof – and always close the door! Don’t be complacent were weeds are concerned and be aware that a beautiful butterfly trapped in your shade tunnel will quickly lead to more caterpillars than you can imagine. I have also found it useful to have a spray bottle of natural pyrethrum nearby to deal with any pests that get through your defences. A properly managed shade tunnel will allow you to grow leafy greens and tender herbs all year round.