Should you keep your spring vegetable covers on or take them off now?
In short: Spring crop covers accelerate growth by trapping solar warmth, but timing their removal is a delicate balance. While these materials protect young plants from wind and pests, leaving them on too long can lead to overheating or hinder essential pollination. Knowing when to uncover your garden is key to success.
Gardeners use various protective materials to give spring plantings a head start. Fleece, typically 25 to 30gsm, is a common choice for converting surplus spring light into warmth. Other options include thermacrop, which offers wind protection, and insect-proof mesh. These covers work by raising temperatures by approximately 2°C, which can advance maturity or flowering by about two weeks. By providing a physical barrier, they also shield young vegetables from wind, hail, and pests like leek moth or cabbage caterpillars.
The choice of material dictates the level of protection. Lightweight fleece allows for better light penetration, while heavier grades provide more insulation against cold. Unlike unperforated polythene, which can cause heat damage or excess moisture, porous fleece and specialized crop covers allow heat to escape, preventing overheating. However, even these breathable materials have limitations. For instance, insect-pollinated crops like strawberries and courgettes should not be covered during their flowering period, as the barrier prevents essential pollination.
Deciding when to remove covers requires observing the weather and the specific needs of the crop. As temperatures rise—often noted by late April or May—the necessity for insulation decreases. While fleece can sometimes remain on throughout the summer to exclude pests, gardeners must monitor their plants for signs of stress. If you are using mesh to protect crops like cabbage and broccoli from pigeons, you might replace fleece with mesh as the season progresses. Ultimately, the goal is to balance the benefits of early growth and pest exclusion against the risk of hindering natural development.
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Sources
- Summary by Intellect · source: Results of different covers on new vegetable plantings in spring, and when to remove
- Also: Fleece and crop covers | RHS Advice
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