Spencer's Epithalamion and Prothalamion both highlight the theme of marriage. However, the Epithalamion celebrates Spencer's own marriage to Elizabeth Boyle, while the Prothalamion is a nuptial song celebrating the respective marriages of Elizabeth and Katherine Somerset (the daughters of the Earl of Worcester) to Henry Gilford and William Peter.
The Epithalamion celebrates the groom and bride's preparations on the day of their marriage. Both the Epithalamion and Prothalamion highlight the importance of nymphs to the wedding preparations. In the Epithalamion, the nymphs cover the bride's path to the bridal bower with flowers. They protect the sanctity of the woods and the lakes so that the bride will have a perfect wedding day. Likewise, in the Prothalamion, the nymphs gather a profusion of flowers in order to braid Katherine and Elizabeth's bridal crowns. Spencer makes full use of pagan images of fertility in both poems.
However, Spencer also celebrates the marriage act in very Christian terms in both works. In the Prothalamion, he wishes Katherine and Elizabeth pleasure in the marriage act and "fruitfull issue" from the consummation of their marriages. The Epithalamion goes still further by describing the bride's physical attractions, and the 10th stanza's paean to the bride's beauty is evocative of the sensual passages from the Song of Solomon.
Her goodly eyes lyke Saphyres shining bright,
Her forehead yvory white,
Her cheekes lyke apples which the sun hath rudded,
Her lips lyke cherryes charming men to byte,
Her brest like to a bowle of creame uncrudded,
Her paps lyke lyllies budded,
Her snowie necke lyke to a marble towre,
And all her body like a pallace fayre,
In the Epithalamion's 11th stanza, Spencer praises his bride's internal beauty: her "sweet love," "constant chastity," "Unspotted fayth and comely womenhed," and "mild modesty." Here, he highlights the Christian definition of unvarnished, inner beauty. On the other hand, the Prothalamion chooses to highlight the mingling of the sacred and the secular in marriage. Spencer contrasts the fairness and whiteness of the twin swans with the muddied waters of the river. The swans represent Katherine and Elizabeth's virginal purity; even the "gentle streame" seems impossibly corrupt and commonplace against this backdrop of feminine perfection.
Interestingly, the Prothalamion chooses not to focus on male (or female) sexual desire, but the Epithalamion hones in on the bridegroom's desire for his bride in Stanza 16. In this stanza, the groom very obviously yearns for the "long weary day" to end so that he can consummate his marriage to his bride. He wants to see her spread out on the bed covered in "odourd sheetes" of "lillies and in violets." In Stanzas 22 and 23, he asks the goddesses Juno, Hebe, and Hymen to bless him and his bride with children:
That we may raise a large posterity,
Which from the earth, which they may long possesse,
With lasting happinesse,
As can be seen, both poems celebrate the theme of marriage; the Epithalamion highlights the personal nature of a marital union, while the Prothalamion also chooses to address the social significance of a marriage union among the nobility (please refer to Stanzas 8 and 9 of the Prothalamion for this). For more about this, please refer to Some Themes in Spenser's "Prothalamion"Daniel H. Woodward, ELH, Vol. 29, No. 1 (Mar., 1962), pp. 34-46, published by the Johns Hopkins University Press.