This rite is usually performed by Nobles of a Familia with one or more fallen members (but not excruciated ones, unless the flowers somehow survive in seed form), who wish to be alerted when the missing Estates of the Familia next become ennobled (in cases where this information is not available from the Imperator). It may only be performed by a surviving member of the appropriate Familia, though once the rite is set in motion anyone may observe the results.
The rite consists of planting the seeds of the flower(s) of each Estate one wishes to inquire after, in soil that has been mixed with dried petals from the flower(s) of the design of the Noble that previously held the Estate. The seeds must be watered with the tears of one of the surviving Nobles for a day and a night to complete the ritual.
The seeds of a fallen Estate will remain dormant until a new noble is chosen for it (unconfirmed reports say that the rite occasionally reveals incipient commencements as well). Near sunset of the day of commencement, the seeds related to that Estate will suddenly sprout, growing to full maturity in a matter of minutes, and blossoming in full splendor in the light of the dying sun, regardless of environmental factors such as temperature, nutrient levels, etc.
The seeds of the Estates of surviving Nobles are usually also planted as part of the rite, as a symbol of unity with those who have fallen. (To fail to do so implies that one is performing the rite against the best interests of the Familia.) Such flowers will blossom in sync with those of newly ennobled Estates, though their seeds germinate normally rather than lying dormant like the other seeds.
The soil used for the rite must be kept free of other plants, or the symbolism of the Familia standing alone against the darkness (or in it, for Powers of the Dark) could be destroyed. In some cases, such contamination causes one or more of the dormant seeds to blossom prematurely or abnormally. In others, the seeds are rendered permanently sterile and worthless. Unfortunately, there is no other indication that something has gone wrong with the rite.
Advanced practitioners of this rite (those with high Spirit) may get results that enable them to gain greater insight into the nature of their new Familia by observing the growth of the flowers. For example, if two flowers of seperate Estates are suddenly twining together, it could indicate a potential close affinity or alliance between the two new nobles, or the fact that both estates are now held by the same Noble. Unusually pale blossoms could indicate a nascent Power of the Dark, unusually vivid ones may mean a power of the Light or Heaven, flowers that send roots, stems, or runners outside the confines of the vessel used for the rite might indicate a power that subscribes to the Code of the Wild, etc. Most such signs are ambiguous to some degree, so this is not an exact science.
Once mature, the miraculous blossoms can be used as part of a special estate-driven divination which will reveal hints concerning the location and identity of the new Noble. (In game terms, the Noble uses a level 0 domain miracle to feel for the connections between her own Estate and that of the new Noble, using the blossom as a bridge.).
Unfortunately, Nobles are slippery (at best) when it comes to divination, and divination itself is an unreliable power, so even the clearest of these hints takes the form of vague impressions and cryptic omens. Of course, once the Noble has correctly interpreted the basic place, it's usually a relatively simple matter to go there and use The Sight to discern who is a Noble and who is not.
Obviously, this rite is a useful tool, but one that most Nobles hope never to need.