שמות ז ,יב: וַיַשְלִיכוּ אִיש מַטֵהוּ וַיִהְיוּ לְתַנִינִם וַיִבְלַע מַטֵה־אַהֲרֹן אֶת־מַטֹתָם:
The Baal HaTurim comments that the word מאתם appears again in the episode of Korach (17:21) "and Aharon's staff among their staffs (besoch Matosom)". He cites a Medrash which relates that there, just like here, Aharon's staff swallowed the staffs of all the other tribes while it was in the Ohel Moed, and that this was the reason that they did not blossom. And it was when they retrieved Aharon's staff from the Ohel Moed that it spat them out. That is why, when the Torah writes "and Moshe took out all the sticks (kol hamatos), the word "haMatos" is written without a 'Vav', since it was really only Aharon's staff that he retrieved. This is why their staves were unable to blossom.
