Affiliate disclosure: As an Amazon Associate I earn from qualifying purchases. This article contains affiliate links.
Choosing between fleece and insect mesh depends on whether your primary goal is temperature regulation or pest exclusion. Horticultural fleece is a soft, fibrous, translucent material designed to insulate plants and accelerate growth by trapping solar warmth. In contrast, insect mesh is a transparent, open-weave polythene barrier designed specifically to block invertebrates while admitting light and air.
Table of Contents
Thermal properties and growth acceleration
The most significant distinction between the two materials is their impact on temperature. Fleece acts as an insulator, trapping heat from the sun to raise the ambient temperature around a plant. This can typically increase temperatures by approximately 2°C, which may advance the maturity or flowering of a crop by about two weeks in spring.
Fleece is available in different weights that dictate its protective capacity. For example, a lightweight fleece (17g per sq m) allows for better light penetration and is suitable for advancing young seedlings. A heavy-duty fleece (35g per sq m) provides greater insulation and is better suited for protecting tender plants from frost. To increase protection in extreme cold, fleece can be double-layered.
Standard insect mesh usually provides little extra warmth, but very fine mesh can significantly raise temperature and humidity. While it offers some shelter from wind and hail, it does not provide the thermal boost required to advance sowing dates or protect against frost in the same way fleece does.
Pest exclusion and mesh specifications
While fleece can exclude some invertebrates, insect mesh is engineered for precision pest control. It creates a physical barrier that is often more effective than chemical pesticides for managing root-feeding insects like carrot fly and cabbage root fly.
The efficacy of insect mesh depends on the hole size (mesh size). Choosing the wrong size can leave crops vulnerable to smaller pests:
- Standard mesh (1.3-1.4 mm): Effective against butterflies, moths, and larger flies such as cabbage root fly and onion fly. It also excludes birds and mammals.
- Fine mesh (0.8 mm): Suitable for smaller insects including flea beetles, cabbage whitefly, and leaf miners (such as allium leaf miner), as well as aphids and greenfly.
- Ultrafine mesh (0.3-0.6 mm): Provides the highest level of protection against very small invertebrates, including thrips.
- Butterfly netting (4-7 mm): Specifically designed to block white butterflies, provided the foliage does not touch the netting.
Weather protection and soil health
Both materials provide a buffer against harsh British weather, but they function differently. Fleece is highly porous, making it less prone to overheating and moisture buildup than polythene covers. It is particularly useful for wrapping tender plants during winter to protect them from wind and hail.
Insect mesh also protects against wind and hail, but it provides a specific benefit regarding soil management. By intercepting heavy rainfall, the mesh reduces the mechanical impact of large raindrops on seed beds and seedlings, which helps reduce surface crusting. Additionally, it reduces ‘soil splash’, which helps keep leafy crops cleaner and reduces the risk of soil-borne contamination.
Practical application and limitations
When applying either cover, the method of installation affects the result. For insect mesh, seal the edges to prevent pests from entering. The RHS recommends burying edges under at least 5cm of soil or securing them to a suitable ground-level board. It is also vital to leave slack in the material to allow for plant growth; stretching the mesh over hoops can widen the gaps and reduce its ability to exclude small insects.
Both fleece and insect mesh share a critical limitation: pollination. Crops that rely on insects for pollination, such as courgettes and strawberries, should not be covered during their flowering period, as the barrier will prevent bees from reaching the flowers. However, self-pollinating crops, such as peas, can be grown under these covers without affecting the yield. For example, using fleece or mesh on peas can prevent female pea moths from laying eggs on the plants during June and July.
Durability and sustainability
There is a stark difference in the lifespan of these materials. Polypropylene fleece is generally less durable; 17g fleece may only last a single year before breaking down into small pieces. It is also more susceptible to damage from animals, such as foxes.
Insect mesh is significantly more robust and can last between five and ten years. Rips in the mesh can often be repaired using patches and epoxy resin glue. From a sustainability perspective, both traditional polypropylene fleece and polythene mesh are difficult to recycle. Gardeners seeking eco-friendly alternatives can look for plastic-free fleece made from sheep’s wool or plant-based materials, and biodegradable insect netting made from plant starch.
Comparison summary for crop selection
To determine the correct cover, consider the following assumed scenario: if you are planting a crop of carrots in early spring and your primary concerns are both frost and carrot fly, a two-stage approach can work. You might start with a heavy-duty fleece to provide the 2°C temperature boost and frost protection during the initial growth phase, then transition to a fine insect mesh (0.8 mm) to maintain a sealed barrier against carrot fly throughout the growing season.
| Feature | Horticultural Fleece | Insect Mesh |
|---|---|---|
| Primary Purpose | Warmth & Frost Protection | Pest Exclusion |
| Temp Increase | Approx. 2°C | Usually low; fine mesh can warm crops |
| Durability | Low (often 1 year) | High (5-10 years) |
| Airflow | High (Porous) | Very High (Open weave) |
| Pest Control | General barrier | Precision (by mesh size) |
Useful products for this job
The links below open Amazon UK product searches. Check the exact item, seller, current price and compatibility before buying.
- Horticultural fleece: Used for frost protection and accelerating growth in early spring. Check the weight (g per sq m); 17g is for light protection, 35g is for heavier frost protection. Search Amazon for Horticultural fleece.
- Insect-proof mesh: Essential for excluding specific pests like flea beetles and carrot fly. Ensure the mesh size (mm) matches the size of the insect you are trying to exclude. Search Amazon for Insect-proof mesh.
Related garden guides
- How to store crop covers so they last longer
- Growing winter salad in a cold frame
- More greenhouse & growing guides
Sources and further guidance
- Fleece and crop covers | RHS Advice
- Insect-proof mesh | RHS Advice
- Pea Moth: How to Prevent Damage | RHS Advice
Guidance researched in September 2026. The feature image is an AI-generated illustration. Product guidance is based on published information, not hands-on testing.