Drying Weed in the Sun: Why Light Hurts Drying Buds

Quick answer: Sun drying is not a method the sources recommend. Extension herb drying guides from the National Center for Home Food Preservation and Maryland say sun drying herbs is not recommended because they lose color and flavor, and Penn State says Pennsylvania’s humidity makes it a poor choice there. UVM Extension says sun drying is uncommon for herbs and flowers for the same reason. Oregon State says hemp flowers are most often dried in a dark room, and that light, air and heat can lower some cannabinoids in stored flowers. A dark, ventilated space is the better place to dry buds.

Can You Dry Weed in the Sun?

You can put buds in the sun, but no Extension source here supports it. Most of the direct advice comes from herb and food drying guides, so it shows good practice for aromatic plants rather than tested results for cannabis.

The herb guides are blunt. The National Center for Home Food Preservation advises against sun drying, because herbs can lose flavor and color in the sun. The University of Maryland Extension says the same and adds that high summer humidity may reduce quality. Penn State Extension says sun drying herbs is not recommended in Pennsylvania because high humidity prevents quick moisture removal. It adds that even at low temperatures, herbs can lose color and flavor when dried outside.

The one source that covers hemp says much the same. The UVM Extension Ag Engineering guide to drying herbs, hops and hemp says drying fruits and vegetables in the sun has a long history. But it says the practice is not common for herbs and flowers, since sun drying costs them color, flavor and volatile compounds, which are often the reason for the harvest.

For cannabis, the aroma and the cannabinoids are the reason for the harvest. That makes the herb guides’ warning worth taking seriously, even though none of them tested buds.

Sun Drying vs Dark Drying at a Glance

What Sunlight and Heat Do to Drying Buds

The sources point to three problems: lost aroma, lost color and uneven control.

Aroma and flavor. UVM Extension says herbs and flowers dried in the sun lose volatile compounds. The Iowa State University Extension herb guide says heat drying reduces flavor, color and essential oils. The Washington State University Extension guide says the sun can get hot enough to volatilize the essential oils that give herbs their flavor.

Color. Every herb guide here lists lost color as a reason to avoid the sun. The Wisconsin Extension herb guide says herbs can be dried outdoors, but they usually keep their color and flavor better when dried indoors.

Cannabinoids. Oregon State University Extension says research has shown that when flowers are stored with exposure to light, air and high temperature, some cannabinoid concentrations can suffer. That finding is about storage, not drying in the sun. Still, it is the closest cannabis evidence here on light, and it points the same way as the herb guides.

Control. Penn State notes that outdoor humidity can keep herbs from drying quickly. Outdoors, you can’t set the temperature or humidity. Oregon State warns that when humidity and temperature are poorly controlled, drying times can run long. UVM Extension explains why a closed room helps. Drying works when dry air passes over the plants, picks up their moisture and is then replaced with fresh, dry air. Indoors, a fan and a dehumidifier keep that cycle going. Outdoors, the weather decides how much moisture the air can take. The National Center for Home Food Preservation describes drying as simply exposing the plant to warm, dry air in a well ventilated area until the moisture evaporates, which a dark indoor room can provide.

For how the drying stage fits with curing and storage, see our top 10 tips for curing and storing cannabis flowers.

How to Dry Buds in the Dark

1. Choose a dark room. Oregon State says slow drying in a dark room, aided by a fan, a dehumidifier or a heater, is the most common way hemp gets dried.
2. Cover branches on the way in. Washington State says to carry cut herbs inside at once, or throw dark cloth or paper over them.
3. Keep the space warm, not hot. Iowa State hangs herb bundles in a dark, warm spot at 70 to 80°F. Oregon State gives 64 to 70°F (18 to 21°C) with 50 to 55 percent humidity for hemp. Wisconsin also gives 70 to 80°F for hanging herbs in a dry, ventilated spot out of direct sunlight.
4. Keep air moving. UVM Extension says a simple box fan can circulate the air in a drying space. It adds that greenhouse fans or blowers can move even more air.
5. Keep humidity in check. NC State Extension says hemp has dried well in buildings where the air keeps moving and humidity holds at 60 percent or less.
6. Hang or spread buds with space. Iowa State calls for small bundles or a single layer on screens.

Heat builds up in piles as well. Washington State warns that cut herbs heaped in even a small pile heat up fast and can start to ferment or rot. Oregon State also describes post harvest steps as a way to preserve the structure of the trichomes on hemp flowers. Our cannabis trichomes 101 guide explains what those resin glands are.

What to Do If You Must Dry Outdoors

The sources don’t describe a safe way to dry cannabis in open sun, and we won’t offer one. What they describe are shaded, covered structures.

UVM Extension says that for small volumes, a window screen set on saw horses in the shade can serve as a drying system. It also says greenhouse and high tunnel dryers usually add 50 percent shade cloth or a temporary shading coat to limit sunlight. The University of Missouri Extension says CBD hemp gets hung to dry in a barn or shed.

If the only space you have is outside, the closest thing the sources support is full shade under a roof, with air moving and buds kept out of direct light. Washington State’s dark cloth or paper cover is one way to keep light off cut plants while you move them. Even then, Penn State’s warning about outdoor humidity still applies. Bring the buds into a dark room as soon as you can.

Troubleshooting Light Damaged Buds

Buds faded in color after drying near a window. Every herb guide here links light and sun drying with lost color. Move the remaining buds to a dark room. Sun drying is not recommended by Maryland or the National Center, since herbs can lose flavor and color.

Buds smell weak after a sunny dry. UVM says sun dried herbs and flowers lose volatile compounds. Dry the next harvest in a dark room. Growers who dry in greenhouses often add 50 percent shade cloth or a kaolin clay coating to limit sunlight, UVM notes.

Buds dried slowly outside on a humid day. Penn State says outdoor humidity can block quick moisture removal. Move them indoors where you can control humidity.

Cut branches sat in the sun before hanging. The National Center for Home Food Preservation adds that harvested herbs should not lie in the sun. Cover them on the way in next time, as Washington State suggests.

Damp buds came in after an outdoor dry. Our post on how to deal with wet weed covers next steps.

Sources

• National Center for Home Food Preservation (University of Georgia), Drying Herbs: https://nchfp.uga.edu/how/dry/herbs
• University of Maryland Extension, Harvesting and Preserving Herbs: https://extension.umd.edu/resource/harvesting-and-preserving-herbs
• Penn State Extension, Preserving Herbs by Drying: https://extension.psu.edu/preserving-herbs-by-drying
• UVM Extension Ag Engineering, Drying and Curing Herbs and Flowers (Hops, Hemp, and Everything Else!): https://blog.uvm.edu/cwcallah/2021/02/23/drying-and-curing-herbs-and-flowers-hops-hemp-and-everything-else/
• Oregon State University Extension, Post harvest processing of hemp flowers: https://extension.oregonstate.edu/catalog/post-harvest-processing-hemp-flowers
• Iowa State University Extension, Growing, Harvesting and Drying Herbs: https://yardandgarden.extension.iastate.edu/how-to/growing-harvesting-and-drying-herbs
• Washington State University Extension, C159 Harvesting Herbs: https://wpcdn.web.wsu.edu/extension/uploads/sites/44/2026/06/C159-Harvesting-Herbs-2026.pdf
• Wisconsin Extension Master Gardener, Drying Herbs: https://mastergardener.extension.wisc.edu/files/2015/12/drying-herbs.pdf
• NC State Extension, Hemp Harvest Timing and Drying: https://hemp.ces.ncsu.edu/hemp-harvest-timing-and-drying/
• University of Missouri Extension, MX79 Harvesting Industrial Hemp: https://extension.missouri.edu/publications/mx79