Floating row covers are lightweight, non-woven fabrics utilized by gardeners and commercial growers to protect crops in the field. They are often called “floating” because they are light enough to be laid directly over plants, though supports are frequently used. The fabric acts as a physical barrier while remaining permeable, allowing air, light, and water to pass through. This ensures crops remain hydrated and receive the necessary sunlight for photosynthesis, even while covered.
Composition and Material Weights
Floating row covers are typically manufactured from spun-bonded polymers, most commonly polyester or polypropylene, creating a durable and breathable gauze-like material. Classifications are based on material weight, measured in ounces per square yard, which dictates performance characteristics.
Lightweight covers, around 0.45 ounces per square yard, are primarily marketed as insect barriers, as they allow the highest level of sunlight transmission, often 90% or more. These lighter fabrics offer minimal frost protection, typically only about 2°F. Medium-weight covers, generally between 0.5 and 1.0 ounces per square yard, offer a balance, transmitting 70% to 85% of light while providing moderate frost protection of 4°F to 6°F, or down to about 28°F.
Heavyweight covers, ranging from 1.5 to 2.2 ounces per square yard, are used mainly for maximum cold protection. They can protect plants from temperatures as low as 24°F to 28°F, offering up to 8°F of frost protection. However, this greater thermal insulation comes at the expense of light transmission, which is significantly reduced to 30% to 50%.
Key Protective Functions
The most common application for floating row covers is to serve as an effective physical barrier against insects and pests. By sealing the edges, the covers physically block pests like flea beetles, cabbage worms, onion maggots, and cucumber beetles. This method provides organic pest management and must be deployed before the pest population becomes established.
Beyond insect control, the covers are valued for weather moderation, particularly for season extension. The fabric traps heat radiating from the soil, creating a warmer microclimate and providing protection against light frost. This micro-environment also acts as a shield, mitigating physical damage to tender seedlings caused by strong winds or hail.
By retaining moisture and slightly increasing the soil temperature, the covers promote faster germination and earlier harvests. Since the material is permeable, the covers can remain in place during rain or irrigation, ensuring that the plants stay watered without requiring the material to be removed.
Installation and Anchoring Methods
Floating row covers can be installed using two main techniques depending on the crop type and the grower’s goal. The material can be placed directly over low-growing, flexible crops, allowing the fabric to be lifted upward as the plants grow. When using this “floating” method, it is important to leave enough slack in the fabric to accommodate the plant’s mature size.
For taller crops or plants sensitive to physical contact, the cover should be supported using structures like wire, metal, or PVC hoops to create a tunnel. This supported method prevents the fabric from rubbing against delicate foliage, causing abrasion damage. Regardless of the support method, the edges of the cover must be thoroughly secured to maintain the pest barrier and prevent wind from blowing the fabric away.
The fabric can be anchored by burying the edges in a shallow trench and backfilling with soil to create a continuous seal. Alternatively, the edges can be weighed down using heavy objects:
- Rocks
- Boards
- Sandbags
- Specialized landscape staples
Anchors should be placed at regular intervals along the entire perimeter to ensure no gaps are present that would allow insect entry.
Timing Their Use and Removal
Timing of application and removal relates directly to the crop’s developmental stage, particularly for plants requiring insect pollination. For fruiting crops like cucumbers, squash, and melons, the row covers must be removed once the plants begin to flower. This removal allows pollinating insects, such as bees, to access the blossoms and facilitate fruit set.
Crops that are self-pollinating or do not produce a harvestable fruit, such as leafy greens, root vegetables, or cole crops, can remain covered from planting until harvest. Covers used for season extension or frost protection should be removed once the risk of freezing temperatures has passed. Growers must monitor temperatures closely, as the covers can cause overheating.
On sunny, calm days, the air temperature beneath the cover can increase significantly, sometimes 20 to 30°F higher than the outside air. Extended exposure to this heat can injure certain crops or lead to flower and pollen sterility in plants like tomatoes and peppers.