They should cling firmly to the central spine and only come apart when the lulav is being shaken. Not Grafted That one should be absolutely certain that the lulav was not grafted, though this does not necessarily invalidate the lulav, particularly in case of an emergency. That the lulav should have only one middle-leaf and not two, though according to some, that is only if they have come apart, but not if they are still attached by means of the brown substance that binds the lulav together. One should take great care, the Elef ha'Mogen adds, to use a new lulav from this year. One should take care not to leave the lulav in water for twenty-four hours.
Many people delight in a green esrog, preferring it to a yellow one.
If it is certain that if one were to leave it in a box for a long period it would turn yellow, then it is kosher, even when it is green. The reason that we make Sukos immediately after Yom Kipur, says the P'sikta, is because on Rosh Hashanah and Yom Kipur, G-d judged and sealed everyone for the forthcoming year. By going willingly from our house into the Sukah, we will have carried out our sentence and fulfilled our obligation, thus exempting ourselves from the need to suffer a far more bitter golus than would otherwise have been our lot. And it's good to know that this idea cuts across the board. Any sentence that we take upon ourselves, exonerates us from a far heavier punishment that we would otherwise have received at the Hand of G-d.