Fibre
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Cotton, Milkweed Jute, Spruce Roots, Bark Fibres, Woven Reeds or Rags can be used as Plant Fibre, as can Abandoned Cobwebs & Tuft of Spider Silk, though they are not a plant.
Milkweed Jute can be obtained by putting Milkweed Roots in a Fireplace or Meatsmoker to make Charred Milkweed Fibre. Using a bucket of water on the charred fibre will create the Milkweed Jute. Alternatively if you can't afford a bucket, you can take the charred fibre out of your inventory and right click it on a water source tile to clean it.