"Not only is Easter called Lieldienas, but the pussy willow has supplanted the palm frond in Christian symbolism. Palm Sunday is Pūpolsvētdiena, literally, Pussy Willow Sunday, and little children are awoken that morning by the ritualistic swats of a willow branch and the exclamation, "Apaļš kā pūpols, apaļš kā pūpols, apaļš kā pūpols!" ("Round like (the catkins of) a pussy willow!") Also used "Apaļš kā pūpols, vesels kā pūpols!" - " Round like Pussy willow, healthy like Pussy Willow!" That way giving a blessing of good health for the year coming until Next Pussy Willow Sunday."
Know also that the Latvian word for pussy willows sounds a bit like the Latvian word for onions--a mistake I won't make twice (although my mom and I would sometimes use onion skins to dye our easter eggs, so maybe that's what tripped me up).