Greenhouse Shade Cloth: How to Choose the Right Coverage Percentage

Shade cloth is one of the most important yet frequently overlooked tools in greenhouse management. The right percentage keeps plants healthy through summer heat while maintaining adequate light for growth. Too little shade and plants suffer heat stress; too much and they become weak and leggy. This guide covers what percentage to use for the most common greenhouse crops.

Why Greenhouses Need Shade Cloth

Greenhouse glazing transmits high levels of solar radiation, which converts to heat inside the structure. On a clear summer day, an unshaded greenhouse can heat up well beyond the outdoor temperature, even in mild climates. This causes heat stress in most cultivated plants and can seriously damage tropical foliage plants that prefer cooler, shaded conditions.

Shade cloth reduces both light intensity and the solar heat load entering the greenhouse. Knitted, UV-stabilized polyethylene shade cloth is widely used in greenhouses because it holds up to multiple seasons of outdoor exposure, its lock-stitch construction does not unravel when cut to size, and its open mesh lets air circulate.

Percentage Guide by Crop Type

The ranges below cover the most common greenhouse crops. For a quick recommendation, the Shade Cloth Selector asks about your application, sun intensity, and color preference and points you to a percentage.

30–40% — Full-Sun Vegetables and Herbs

Tomatoes, peppers, cucumbers, zucchini, eggplant, and basil thrive in full sun but benefit from 30–40% shade during the hottest months to prevent heat stress, blossom drop, and sunscald. At 30%, light intensity remains high — the shade primarily reduces heat load rather than limiting photosynthesis.

40–50% — Mixed Crops and Nursery Stock

For hobby greenhouses growing a mix of vegetables, herbs, and starts, 40–50% is the most versatile range. It protects heat-sensitive seedlings while still providing adequate light for productive crops. This range is also common over propagation and nursery benches during summer.

50–65% — Cattleya Orchids and Tropical Foliage

Cattleya orchids, anthuriums, peace lilies, pothos, and many tropical foliage plants do best at 50–65% shade. Filtered sun prevents bleaching and leaf scorch while maintaining enough light for healthy growth and blooming. Cattleyas are among the higher-light orchids — too much shade produces thin, weak growth and poor flowering.

70–90% — Phalaenopsis Orchids, Ferns, and Deep-Shade Plants

Phalaenopsis orchids, maidenhair ferns, Boston ferns, mosses, calatheas, and other low-light plants need significant shade. At 70–90%, only 10–30% of sunlight reaches the plants. Phalaenopsis generally do well in the 70–80% range; the heaviest densities (87–90%) suit deep-shade plants and side curtains.

Quick-Reference Comparison

Interior vs. Exterior Mounting

External (recommended for cooling)

Mounting shade cloth on the outside of the greenhouse frame blocks sunlight before it enters the structure, so less solar radiation converts to heat inside the glazing. For that reason, external shade cloth generally provides more cooling than the same percentage installed internally. Finished shade cloth with taped edges and grommets pairs well with S-hooks or bungee cords for quick seasonal removal.

Internal (easier to install)

Interior shade cloth is installed on the inside of the rafters or ridge pole. It is easier to install and adjust, but light enters through the glazing and converts to heat before the shade cloth intercepts it, reducing cooling efficiency. It works best when precise light-level control matters more than maximum temperature reduction.

Measuring Your Greenhouse for Shade Cloth

For a flat sidewall or end wall: Measure width × height and add 12 inches on each dimension for attachment overlap.

For a gable roof: Measure slope length from ridge to eave and the width of the greenhouse. For a single piece covering the full roof, add 24 inches to both dimensions for draping over the ridge and eaves.

For interior horizontal installation: Measure interior width and length; add 6 inches to each for edge overlap at attachment points.

Pro Fabric Supply’s knitted shade cloth uses a lock-stitch construction, so it can be cut to size with scissors without unraveling. Cut pieces have raw edges; finished shade cloth comes with taped edges and grommets every two feet, ready to hang.

This is a general guide. Light requirements vary by species, cultivar, climate, and season, so watch your plants and adjust shade levels as needed.