"Rabban Yohanan b. Zakai used to say, 'If there was a planting [seedling] in your hand and they told you, "Here's the M'shiah [Messiah]," plant the seedling and afterwards go and greet him.'" I recognized this famous saying, but then I did a double-take. This chapter is "The Land of Israel," and this section is "The Land and its Settlement." What is this saying doing here? I've always understood this statement as a caution about over-eagerness for the M'shiah, perhaps a warning to be suspicious of a purported but possibly-false M'shiah, and a prioritization of small accomplishments in this world over focusing on the next world. None of this has anything to do specifically with the Land of Israel.
My guess is that B&R understood "planting" in light of text 3:2:22, about planting being the first activity the people is to undertake upon entering the Land. But then Rabban Yohanan b. Zakai's statement means something a bit different from what I thought it meant: now it's a statement about how important it is to plant in the Land of Israel -- it's so important that one even delays greeting the M'shiah in order to finish planting. Instead of an attempt to hold in check possible over-enthusiasm for the M'shiah, the statement accepts that enthusiasm and elevates planting in (and, it follows, settlement in) the Land even higher.
I wondered whether commentators on the original text might have explained the text in ways that would support B&R's apparent reading or my reading. Unfortunately, B&R cite the statement only to Avot d'Rabbi Natan version B. Schechter's text does not have any explanatory comment on this statement, and the version that appears in a standard set of Talmud is version A. (Likewise, Goldin's book on Avot d'Rabbi Natan uses version A.)