The rotem is referred to a few times in the Old Testament. The rotem is identified as broom in the NIV. The main broom species found in Israel is the white broom (Retama raetam). Recently another broom tree, the Retama caper was discovered in the southern Aravah. This was after it was thought to be extinct for about 50 years.

The white broom has white flowers which appear in February and March. It grows to about three metres tall and may reach up to six metres across. This provides shade for those who are exposed to the hot desert sun, and make sense for Elijah to find shade under it as I Kings 19 records. It has a short trunk which branches out from the base, with what are best described as drooping branches. 

Retama raetam

The white broom (Retama raetam). PICTURE: Ariel Palmon (licensed under CC BY-SA 3.0)

The broom can survive in poor sandy soils and they are found in arid regions of Israel such as the area around Beersheba. Israeli botanist Nogah Hareuveni points out that, "the rotem is one of the most effective plants for holding back sand dunes. Ratam in Hebrew means to harness, rein in, hold; hence perhaps its Hebrew name." 

The genus of Retama (broom bushes) are native to North Africa, the area of the Levant (Israel and Lebanon) and some parts of southern Europe. 

Job speaks of the mocking of the young men, as like eating the roots of the rotem:
"But now they mock me,
men younger than I,
whose fathers I would have disdained
to put with my sheep dogs.
Of what use was the strength of their hands to me,
since their vigour had gone from them?
Haggard from want and hunger,
they roamed the parched land
in desolate wastelands at night.
In the brush they gathered salt herbs,
and their food (literally bread) was the root of the rotem (broom) tree." - Job 30: 1-4
The white broom roots are very bitter and so Hareuveni suggests that the passage means that the roots were actually being sold to be used as kindling, in cooking stoves. 

A 19th century visitor to Palestine, Johann Ludwig Burckhardt, observed the Bedouin of the Sinai burning the roots of the Retama into coal. He said that they make the best charcoal and throw out the most intense heat. This image is mentioned in Psalm 120: "He will punish you with a warrior's sharp arrows, with burning coals of the broom tree."

According to Hareuveni, the embers of the white broom tree "retain fire and heat long after they appear to be dead ashes".

When fleeing into the region of Sinai, Elijah sat down under a rotem to keep out of the hot desert sun:
"Now Ahab told Jezebel everything Elijah had done and how he had killed all the prophets with the sword. So Jezebel sent a messenger to Elijah to say, 'May the gods deal with me, be it ever so severely, if by this time tomorrow I do not make your life like that of one of them.' 
     "Elijah was afraid and ran for his life. When he came to Beersheba in Judah, he left his servant there, while he himself went a day’s journey into the desert. He came to a rotem (broom tree), sat down under it and prayed that he might die. 'I have had enough, Lord,' he said. 'Take my life; I am no better than my ancestors.' Then he lay down under the tree and fell asleep.
     "All at once an angel touched him and said, 'Get up and eat.' He looked around, and there by his head was a cake of bread baked over hot coals, and a jar of water. He ate and drank and then lay down again. 
     "The angel of the Lord came back a second time and touched him and said, 'Get up and eat, for the journey is too much for you.' So he got up and ate and drank. Strengthened by that food, he traveled 40 days and 40 nights until he reached Horeb, the mountain of God. There he went into a cave and spent the night." - I Kings 19:1–9

Hareuveni made this comment regarding the white broom: "The traveller who looks on the ground beneath the white broom will also be able to see the mattress that served Elijah when he slept under the broom: a layer of thin, dry branches that drop off in the arid periods when the bush cannot supply nourishment to all the branches."

A similar situation happened with Abraham’s concubine Hagar - and in a similar area to Elijah too. Hagar also sat down under a ‘bush’ to keep out of the hot desert sun. Although it is not specifically referred to as the rotem (rather the general word for plant, se’ach, is used) it is possibly the white broom that is being referred to in this passage.

"Early the next morning Abraham took some food and a skin of water and gave them to Hagar. He set them on her shoulders and then sent her off with the boy. She went on her way and wandered in the desert of Beersheba. 
     "When the water in the skin was gone, she put the boy under one of the bushes (se’ach). Then she went off and sat down nearby, about a bowshot away, for she thought, 'I cannot watch the boy die.' And as she sat there nearby, she began to sob. 
     "God heard the boy crying, and the angel of God called to Hagar from heaven and said to her, 'What is the matter, Hagar? Do not be afraid; God has heard the boy crying as he lies there. Lift the boy up and take him by the hand, for I will make him into a great nation'." - Genesis 21:14–15.

This is an edited excerpt from Alvin Johnson's iBook 'Biblical Flora', 2017. The book is available for free download on iTunes. A teacher's edition is also available for purchase.