How to provide frost protection for plants
Many non-native plants adapt to the changing weather conditions via their innate ability. With warmer climates and the want for more exotic plants in UK gardens, it's now not unusual to see palms, banana plants, yuccas or even Bird of Paradise plants. However, these and their exotic cousins often require additional assistance during a harsh British winter. There are now good options available to provide frost protection for plants; garden fleece is one such solution. In this article we’ll look at the versatility of 'garden' or 'horticultural' fleece, from protecting plants from frost, to providing crop cover. Helping you to decide the best garden fleece for you, as well as providing guidance on how to protect plants from frost.
Does fleece protect plants from frost?
A good quality fleece will protect plants from frost providing that it’s the right type. The fleece material creates a partial barrier to moisture. Whilst remaining breathable, it forms an air pocket that provides higher temperatures inside. Tiny water droplets in the air become trapped on the outer fibres of the fleece and ‘bead’ on, or near, the surface. These droplets may freeze if the air is cold enough, but the trapped air inside remains drier and slightly warmer. This makes it harder for frost to form on the plant nestled inside.
What is garden fleece made of?
Gardeners sometimes use their own 'home-made' garden fleeces. However, for effective frost protection, understanding the material composition of a garden fleece is important. This knowledge allows you to assess whether it will offer adequate protection during the winter months.
Select a heavy-duty frost heavy-duty non-woven polypropylene when deciding on your frost fleece. The term 'heavy-duty' might raise concerns about whether the weight of the fleece will pull down plants. However, properly constructed fleece products are quite light.
The best horticultural fleece typically consists of polypropylene fibres. Manufacturers spin these fibres into a loose sheet and then bond them together to achieve a uniform density. It's possible to find several different densities or weights of fleece available. Manufacturers typically group these into two categories: 'light' and 'heavy duty'.
Most make-shift solutions force compromise. Selecting a good quality horticultural fleece offers many benefits:
- Better heat retention
- Lighter weight
- Reduced water absorbancy
- Quicker drying
A good quality garden fleece will perform better, even under harsher conditions.
Does garden fleece let through water and light?
A question often posed, ‘does garden fleece let through water?' This is usually born of the concern that water will permeate through and freeze. Thus, not protecting the plant as imagined. However, that's not how plant frost protection with fleece works.
Garden fleeces do let water through. The quantity will vary depending on the weight or gauge of the material, and how you have used it. Light weight fleece will allow more water to penetrate, especially under heavy rain.
Heavier garden fleece will block more rain, up to a point. However, all good garden fleeces will also allow water to drain or ‘wick’ quickly out of the material.
If you have installed a fleece as a jacket around a plant, much of the material will be positioned around the vertical. Horticultural fleece wicks water away best when positioned in this way.
Similarly, one might also ask whether garden fleece allows light to pass through? All gardening fleeces will reduce the amount of sunlight that gets through to your plants. Typically, the lighter materials allow through the most light and heavier duty fleeces cut more out.
For this reason, you should only keep a fleece cover on your plants for as long as necessary. However, as winter turns to spring, more light will pass through the fleece. When combined with the advantage of a warmer environment and air circulation, the fleece cover proves its worth. It enables the transfer of plants outside, on average, two weeks earlier than normal.
Providing frost protection for plants and pots
When you’ve spent money buying striking large pots, or time caring for exotic plants in your garden, it's disappointing to see the elements impact them. Hard winters can be a cause of mishaps only noticed in the spring.
When you have a plant species for which frost is a concern, it's important to take measures to before the freezing conditions start. This will depend on the charteristics and hardiness of the plant. Established bay trees can generally withstand the cold, although they may struggle when temperatures plummet to -5°C or below. Banana trees, on the other hand, can only withstand minor frost.
Creating plant covers for winter
Installing gardening fleece to create plant covers for winter can take time, but isn’t physically demanding. A single wrap of heavy-duty fleece will may be enough for many species during most winters. A double, or even triple, layer being the best option if you only have thinner fleece at your disposal.
Plant cover steps
- Assess each plant that you want to wrap before you cut your fleece to size. Make sure to allow for some overlap. Don’t wrap too tightly, a loose fit will trap air effectively, whilst putting less stress on the plant.
- Draw together fleece wraps and tie them in place with garden twine or a thin cord. Secure above the top of the plant and again at ground level - around a pot or the base of a central stem. Make sure to allow plenty of fleece for drawing into each point of closure.
- Consider covering the main stem of some plants with a layer of fleece first, before doing the same to the mass of foliage. This will benefit more frost sensitive plant species.
Plants in pots
Fleece can protect plants in pots from harsh conditions. A single or double wrap of frost fleece will keep most potted plants safe through the winter.
Natural insulators, like straw or a loose bark mulch, can be included for additional peace of mind. When using these, place them around the base of the pot and over the soil before you wrap it up.
Remember to remove the fleece when the temperatures rise. Problems with mildew and rot can arise if a fleece is left on too long.
What is crop cover?
'Crop cover' refers to a material (or sometimes method) used to protect crops from various external factors like extreme weather (such as frost) or excessive sunlight. Sometimes a crop cover is also used to protect from birds, insects or other animals.
Aside from frost protection, you may also want to shield against heavy rain and light hail. Horticultural fleece has superseded old-style polythene sheets for crop protection in this capacity.
Fleece provides the benefits of improved airflow, and moisture retention below the cover is greatly reduced. This helps to prevent issues from older methods, like overheating in sunny conditions and ice build-up under the cover when the sun goes down.
Fleece used for crop-cover needs to be lightweight, as it is usually draped directly over plants without the support of hoops. Thinner varieties of horticultural fleece can be more prone to being torn. Therefore installation should be managed carefully. However, once in place, with edges normally pinned down, the benefits are immediate.
The temperature under the fleece will be held slightly higher than the ambient temperature, pests will find it harder to get at the plants, and the rate of growth should increase.
The improved conditions for the intended crop will also be helpful for weeds, so do look from time to time. Remember to remove crop cover fleece as soon as the weather warms; this will make it harder for rot and disease to get a foothold on the crop.
Ground cover for vegetable beds
Utilising a good quality garden fleece to pre-warm a vegetable bed before sowing can be effective in helping deliver earlier crops. This method involves covering the soil with a layer of garden fleece 2-6 weeks prior to sowing seeds.
The fleece acts as an insulator, trapping heat and raising the soil temperature, which is particularly beneficial during the early spring months when the air is still cool. Pre-warming can encourage seeds or seedlings to germinate faster and exhibit stronger initial growth when sown.
How to use horticultural fleece on pots
When it comes to wrapping pots for the winter months, using a thin fleece could work. However, better results would be acheived using a thicker, heavy-duty garden fleece. A single wrap (with a bit of overlap) of this around a pot will do a good job of protecting the pot and plant roots. Apply an extra wrap for very cold periods.
It’s a good idea to check that the base of the pot won’t be standing in water for any length of time. This could wick into the fleece and reduce its insulating properties.
Garden fleece reuse
Better quality fleece normally outlasts cheaper products, producing less waste. It also potentially allows for repeated reuse, offering better value for money.
You can wash and reuse thicker fleece, keeping a little less waste from going to landfill. And, when horticultural fleece gets damaged, it can be cut into smaller pieces - these can be used as multi-layered insulating wraps on pots and plant stems.