Nine in the second place is a favourable line, and what it favours is an unequal attachment that draws on something below rather than above. A querent here is typically strong in the matter at hand and short of whatever grounds it, and the line indicates that a connection with a weaker, earlier or less established party will supply what strength alone has not. The decayed willow putting out shoots is the operative picture: new growth appearing low down on old wood, which is where willow shoots actually come from.
The reading should not be split off from the text's own comparison, an old husband taking a young wife, called advantageous in every way. That valuation belongs to the Zhou period, framed by a society that measured a union by the heirs it might produce and applied different standards to the ages of the two parties, and it is reported here as it stands rather than tidied. What carries over into any other setting is the structural point the willow makes on its own. This line reaches downward, and downward is where a root can form.
When the line changes, the lower trigram Xun becomes Gen and the figure becomes Influence, King Wen 31, the hexagram of mutual attraction between two parties who genuinely answer one another. The movement confirms the reading. An attachment that begins with one party supplying what the other lacks is on its way to becoming reciprocal, which the fifth line's mirrored image never manages.