We see here another example of details appropriate to nocturnal actions. Odysseus and Diomedes could leave these spoils behind without worrying that someone else will take them during the night; instead, the concern is that they may not be able to find them again in the darkness, hence the need to make a sign conspicuously or clearly (δέελον δ᾽ ἐπι σήματ᾽ ἔθηκε, 10.466). Odysseus creates such a sign by tying the branches of the tamarisk tree (a large, dense, shrub-like tree) to the reeds below. We will see later, of course, that this sign works, when Odysseus and Diomedes stop and pick these spoils up on their return (10.526–529). This sort of planning is necessary in the dark.
The tamarisk grows often near water, and the reeds mentioned here also suggest a wetland environment, perhaps the bank of a river. We see these characteristics of the plant in its other appearances in the Iliad: Achilles leans his spear against a tamarisk before he leaps into the Xanthos river to kill the Trojans he has forced into it (Iliad 21.18) and later, when Hephaistos sets the corpses in the river on fire, tamarisks are among the plants listed as burning along the river (Iliad 21.350). The denseness of the plant is seen at Iliad 6.39, when the horses of Adrestos become tangled in a tamarisk and his chariot is broken, setting the horses loose. We have seen that a woody or marshy area—that is, one filled with plants—is often chosen for an ambush (see “The Poetics of Ambush”), and the tamarisk itself may also have a particular association with ambush. In the Homeric Hymn to Hermes, the god, who is called “a robber, driver of cattle” (ληϊστῆρ’, ἐλατῆρα βοῶν, Homeric Hymn to Hermes 14) and “a spy at night” (νυκτὸς ὀπωπητῆρα, Homeric Hymn to Hermes 15), among other epithets, is himself associated with the night and the ambush theme, as we also see in his role in guiding Priam during Priam’s infiltration of the Achaean camp in Iliad 24 (see “The Poetics of Ambush” and above on 10.1ff. for fuller discussion). According to the hymn, on the evening of the day he is born, Hermes steals the cattle of Apollo (see “The Poetics of Ambush” also for how cattle rustling is part of the larger ambush theme). When Hermes is driving these cattle at night, he stops and makes himself sandals, weaving together tamarisk and myrtle branches (συμμίσγων μυρίκας καὶ μυρσινοειδέας ὄζους, Homeric Hymn to Hermes 81). Odysseus ties together tamarisk and reeds here in another kind of weaving of this plant, accompanying another night ambush. Schnapp-Gourbeillon (1981:115) suggests that this plant has religious associations (see also Wathelet 1989:221n35).