Well,
grapefruit do not root as quickly as citrons, lemons or limes. I found that Volkamer and Rangpur are the most fasted twigs to root....
So more difficult are oranges, sour oranges and grapefruits, most difficult I found Pomelos, Kumquats and most mandarines.
So for the more or less difficult to root cultivars I use a rooting hormone, like Rhizopon AA 1%, which helps me to ensure root development.
To root a citrus twig, use a part about 8 to 10 inches long, left only 5 to 6 leaves attached, and cut those leaves with a very sharp, disinfected prunning shears about half, so only half leaves will remain on the twig.
Do a fresh cut close to a node at the base, and dip into the rooting hormone, if you consider necessary and stick it right into a sterile and infertile rooting media.
Mixtures or half sand and half peat moss, or half sand and half coconut fiber should be very well for rooting purposes.
Maintainace of a good rooting media temperature, of about 23 up to 24°C (25 up to 77°F) helps most to get good root development.
Provide a humid environment. Media should be moist, but not wet or dry. The air humidity needs to be close to saturisation, because without roots the plant cannot compensate water loss, so a saturisated air humitidy is benefical for the root development of the cutting.
So I use a indoor greenhouse for the windowsill, and there are a lot more indoor greenhouses which fit best for rooting a cutting.
Ofter simply take a pot, put in some self made dirt, stick the cutting and place a clear plastic bag over the pot and close it at to pot's top with a rubber band... and it works....
so, you can surely give it a try... only two things can happen: The cutting roots, and you have a new plant, or the cutting wilts and shrivels up dry, and it failed...
