Those trees, however, that grow in close compact are competent owing to mutual dependence to resist winds more violent still. Thus he that is single, however, endowed with all the virtues, is regarded by foes as capable of being vanquished like an isolated tree by the wind. Relatives, again, in consequence of mutual dependence and mutual aid, grow together, like lotus-stalks in a lake.

In plain words: Vidura continues that trees growing close together hold each other up against even stronger winds. A person who stands alone, however good, is easy for enemies to defeat. Relatives who depend on and help each other grow together, like lotus stems in a lake.