What does “angelorum planta agmini” mean?

Question

I at least partially understand all the invocations in Litaniae in omni tribulatione, but one stays mysterious: "Angelórum planta ágmini" It's quite Google-proof, a quoted search for it returned only references to the litanies. The oldest surviving record of the litanies is from circa 1400 AD, but they are older, perhaps even composed in the first generations of Dominican friars in 13th century.

Analyzing the text, I understand the first word for certain (plural genitive of "angelus"). The second word could be either singular vocative of noun "planta" or singular imperative of verb "planto, plantare" (the verb seems to fit the context better, but I'm not sure), and I have no idea with the third word.

Answer 1

The only way I can interpret this is as follows, although I am not certain:

[Maria, you are] an offshoot to the train of angels.

So planta is like the tendril of a larger thing, or like a foot planted down somewhere as a first 'base of operations'. Maria came to earth 'representing' or foreshadowing the angels that will probably come down from Heaven on the Day of Judgement, or something like that. Agmen means "multitude, train", as in a moving army.

The dative agmini is somewhat odd. And I don't know how common this metaphor of feet or sprouts of the multitude of angels is. But it's the only thing I can think of. And it isn't classical Latin, so new or uncommon constructions or senses are not unexpected.

Answer 2

I consulted the litannies and Cerberus' translation with my Latin teacher and he offered an alternative translation.

The other invocations in the strophe make rhymes by dativus commodi sive incommodi, so the dative should be of this kind in "angelorum planta agmini" as well. "Planta" means a sprout or shoot (as in Cerberus' translation) and "angelorum agmini" means "for the angelic army".

The theological interpretation is that though the number of angels is constant (since the fall of angels, when some became demons), new celestials and thus other members of "the angelic army" grow in us, who can hope in joining angels in heaven. Eternal life somehow starts now, so the metaphor of a plant growing from a sprout here on Earth to a tree in Heaven can be applied to every Christian (including "anonymous Christians"). Mary is the best one and a perfect example in this way (she become not just equal to angels, but a queen of angels!), and growing of others into the angelic level may be seen as possible only through Mary's help (or better, through her son Jesus Christ who wouldn't grant us this privilege without being born of Mary), so this title can be applied to her in some stronger sense than to anyone else.