THE PALMS — In central Europe, large clusters of plants, interwoven with flowers and adorned with ribbons, are fastened to the top of a wooden stick. All sizes of such palm bouquets may be seen, from the small children's bush to rods of ten feet and more. The regular "palm," however, consists in most European countries of pussy willows bearing their catkin blossoms.

http://www.catholicculture.org/liturgicalyear/activities/vie...

Am Palmsonntag versammeln sich die Kinder vor der Schule und gehen dann mit dem Palmbuschen durch den Ort bis zum Marktplatz vor der Kirche.

Dort findet bei schönem Wetter dann die Palmweihe statt. Die Weidenzweige für den Palmbuschen werden selbst ge-pflückt, und mit Brezeln, ausgeblasen-en, bemalten Eiern, Hobelspänen, Kreppapierstreifen und mit kleinen Äpfeln geschmückt.

http://www.raurisnet.at/kultur/brauchtum/palmbuschen.htm

The Palmbuschen is made from a wooden pole, which can be up to 2,5 metres tall, to which people attach twigs from willow (before it flowers), and evergreen trees like yew, juniper and boxwood. The Palmbuschen is then decorated with pretzels, apples and coloured ribbons.

After the Palmbuschen has been completed, people take it to a church so that it is blessed. They then take them around the fields, which are thought to bring good luck for harvests.

http://www.plantscafe.net/media/files/enar06_MG_Art_M6_Cultu...

You could use this phrase. As far as the "Palmkätzchen" I would simply say "Blessing of Pussy Willow Branches".

Lots of Google hits not only relating to Catholic liturgy but also tourist-related articles talking about Palm Sunday in southern Germany and Austria