Translation:He used to speak to his grandmother every morning.
Could you also translate this as "He usually spoke...", or would you have to use "tale" in the past tense instead of the infinitive for that? ( - since "plejer" has been translated as "usually" while in its present tense form)
The translation for 'at pleje' as 'usually' is .. not a very fortunate one. 'Pleje' is a verb, of course, and should be treated as such, but the English language doesn't have a present form of 'used to'. You -could- translate the sentence like so, but I would recommend keeping the structure rather close to the given sentence.
The actual translation of 'usually', the adverb, is 'sædvanligvis', so you'd go with "Sædvanligvis talte han med sin bedstemor hver morgen."