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Dublin: 11°C Saturday 29 January 2022

When to use horticultural fleece: 'The Irish spring can bite you in the bum'

Let’s hope that’s the end of the cold nights for this year, writes Michael Kelly.

Michael Kelly Grower

I AM PRETTY sure that most years in these pages, I have advised against complacency when it comes to how the Irish spring can bite you in the bum. And this year, I completely ignored my own advice.

Lulled into a false sense of security by the longer days, the growing grass, the emerging leaves and the blossoms on trees, I’ve been in full-on spring mode over the last few weeks. Last week we planted out 70 tomato plants in the big tunnel, and I also transplanted a load of spinach and beetroot seedlings in the veg patch outside.

Polar air in spring

And then? I went out on Tuesday morning and was alarmed to discover a thin layer of frost on the windscreen of the car. Temperatures had plummeted overnight with a blast of polar air bringing colder air temperatures.

Though it seems like a temporary blip, and warmer temperatures are on the way this weekend, we were down as low as 0 degrees at night this week. For most of the week I was fretting, in particular, about the tomato plants.

It’s not the end of the world if I lose a few dozen beetroot or spinach seedlings, but the tomato plants are an altogether more valuable affair. From a pure monetary perspective they are probably worth €5 per plant at this stage, and from an end produce prospective, they are worth far more than that.

Let’s say that a healthy plant can produce 300 cherry tomatoes and that a punnet of 20 organic tomatoes would cost you €3, that means each plant can produce €45 of tomatoes in a season. That means the crop is worth over €3,000. Yikes.

A worrying week

Of course, the monetary value is only part of the appeal. The sheer deliciousness of the tomatoes and the fact that I can “store” them as sauces for the freezer, sundried tomatoes and tomato ketchup, gives them a value way beyond what they are worth if I had to buy them.

So we’ve been keeping a close eye on the plants this week, ready to roll out fleece on top of them at night. The sunny weather during the day at least is a bonus, warming the polytunnel by day and it will hopefully retain some of that heat into the night to keep the temperatures up a few degrees.

Spare a thought for our commercial apple producers, who must be having a particularly worrying week. Cold nighttime temperatures are particularly damaging to fruit trees. Temperatures that drop below freezing can cause significant damage to fruit blossoms, particularly when the blooms have opened (as they certainly have in our garden).

Significant damage can be caused to full blooms at temperatures lower than -2 degrees Celsius and trees will lose over 90% of their fruit if the temperature drops to -4 degrees Celsius.

So, let’s hope that’s the end of the cold nights for this year.

The Basics – Horticulture Fleece

shutterstock_579235027 Source: Shutterstock/theapflueger

Horticultural fleece is a useful piece of kit for the home-grower, particularly in the spring when you are trying to get seedlings established outside and we’re still vulnerable to frost. Aside from frost protection, fleece can simply help plants to grow more quickly in the spring when temperatures are relatively low. It will generally increase temperatures by about 2 degrees Celsius, which can bring plants along by about two weeks.

Fleece is white, light and soft to touch. You can buy it in small quantities (cut to size) in garden centres, or in larger rolls if you need a lot. You can cover a row of seedlings with a layer of fleece, using some soil to weigh down the sides. They can be used with or without hoops.

For frost protection I generally just lie the fleece on top (it’s very light). Fleece can be bought in different grades. Light fleece gives less protection but better light penetration (and is cheaper). It is more inclined to tear than heavy-duty fleece.

Fleece can also be used for pest protection. For example, I often use fleece to cover my carrot crop to keep the carrot root fly away or to keep the cabbage white butterfly off brassica (kale, cabbage etc) plants.

Recipe of the Week – Sesame Pak Choi

shutterstock_567755959 Source: Shutterstock/iMarzi

We have beautiful small pak choi leaves in the polytunnel now – it seems to do better in the polytunnel in the spring than it does in the heat of the summer. Here’s a lovely way to cook it.

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This recipe, which serves six people, looks for 9 pak choi. I never wait for pak choi to form a “head”, but pick the tender leaves instead and allow it to sprout again – so I halved the quantities before cooking this recipe.


  • 9 pak choi
  • 2 tbsp groundnut oil
  • 2 tbsp toasted sesame oil
  • 1 large garlic clove, crushed and finely chopped
  • 1 mild green chilli, seeded and finely chopped
  • 1 tbsp Thai fish sauce (optional)


If using full heads of pak choi, cut a thick slice from the root to separate the leaves. Rinse and drain.

Heat the groundnut oil in a large wok over a medium heat and add 1 tbsp sesame oil, the garlic, chilli, fish sauce (if using) and pak choi.

Toss until coated and clamp a pan lid over them. Reduce the heat and cook for 3-6 minutes, tossing occasionally, just until the leaves have wilted (the stalks should be tender-crisp).

Add the rest of the sesame oil and salt. Toss the leaves and serve immediately.

Michael Kelly is founder of GIY and GROW HQ. 

Click here for more GIY tips and recipes.


About the author:

Michael Kelly  / Grower

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