Here are relevant references from the Books where reeds are mentioned.
I make no pronouncements on these matters, but report them as I find them.
Arrive at your own conclusions.
I wish you well,
Another of the new girls was thrown over one of the benches; she lay on her back; her head was down, her dark hair, long, wild, was in the dirt and reeds, strewn on the floor of the hall;
Marauders of Gor Book 9 Page 93
For an instant I was conscious only of the dirt floor, the reeds strewn upon it, the mad forest of running feet.
Marauders of Gor Book 9 Page 205
The man left tracks by the side of the pond, and then waded into the chill water. He broke off a reed and then waded deeper into the water.
The bow of the rence craft, still dry, nosed through reeds. Other craft, too, were about.
A gant suddenly fluttered out of the reeds, darting up, then again down, away.
Ellen stirred, awakening, on her stomach, lying in the mud, half in the water, amongst the reeds, clinging still to the wreckage of her basket.
There were two of them, standing in the water, one on each side of her. She did not look up, but hooked her fingers tightly in the remnants of the wicker.
"Let us see her," she heard.
Her fingers were then loosened from the wicker. It was then thrust away, back into the water. Her fingers dug into the mud of the shore, the water lapping softly about her. She then felt herself being turned about and put to her back.
About dawn she reached the shore and lost consciousness amongst the reeds.
The water there, say, some three or four yards from shore, was some eight to ten inches deep. It moved about her and between her thighs. It felt chilly and gritty. Under the water she felt the mud, slippery and cold, beneath her toes and knees. A breeze came over the water. It moved her hair just a little, she felt it on her arm, and it rustled beyond her, through the reeds.
She heard the younger lad now splashing through the reeds. In a short time he returned and her hands were bound behind her back. The rope was long enough to serve as well as a leash, and, moments after she had been ordered to her feet, some yard or so of it, rising from her confined wrists, had been looped and knotted about her throat, its free end then, some five feet or so in length, serving as a leash. Ellen knew that sometimes even desiderated slaves, before a submission ceremony, were put on a simple camp rope and led about, that they would better understand their condition and status, that of a domestic animal, but in her case the rope was not symbolic in nature, but effected a simple utility, constituting a device for keeping and controlling a girl. Ellen, bound, was led on her leash, stumbling, wading, through the reeds.
"Twice," said Tajima "tarnsmen returned, circling about, at a great height, and we must conceal ourselves, once in the reeds and mud near a small stream, once in leaves and brush."