Diooeae (a tribe of cycads); -----

Aizoaceae (family of African succulents),

  Aloeaceae (a family divided from Liliaceae in some classifications); -----

Aecidiaceae (plant family (synonym?)),

  Paeoniaceae (family of flowering plants),

  Saurauiaceae (Chinese gooseberry family, synonym of Actinidiaceae); -----

Fouquieriaceae (family of arid N. American flowering plants) - Longest with 1, 2, 3, 4 consonants.

Coccaceae (bacteria), Nioniinae (cicadellid) - Longest with 1 different consonant.

Araucariaceae (southern hemisphere gymnosperm family) - Longest with 2 different consonants.

Hantzschia (diatom), Eschscholzia (poppy), Eleutherodactylus karlschmidti (extinct tree frog), Rhododendron camptschaticum, - 6 consecutive consonants.

Schtschurowskia Regel & Schmalhausen, 1882 (Umbelliferae) - 7 consecutive consonants.