I have a couple of questions about flowering plants (indoor/outdoor). When a flower dies is it necessary to remove it from a plant? If so, I read that it was beneficial to leave it in the plant's soil? Is there any truth to this?
Removing dead/dying flower: Yes, it promotes more flowering/blooming for newer buds/blooms. It's not necessary for survival for most plants. There are the odd ones that stagnate such as dahliettas if not "dead headed" consistently. Putting flower in soil: It may be beneficial in the sense that it's compost material. Usually flowers, fallen leaves and other debris are cleared from the soil area and lower branches/leaves to prevent mold and fungus from growing and keeping pests or disease away. I've not particularly heard about purposely putting flower remains in the soil being beneficial. It'd be a waste of time to me.
Yes, absolutely cut off old blooms! On everything but orchids (these you should leave until the whole spike is through flowering) it's very good for the plant's health. Not vital, except for some of the aster-type flowers, but a very good idea nonetheless. The only case for not removing spent flowers is if you're anticipating fruit from the plant - it would be counterproductive of me to deadhead my Fuchsia boliviana, for example, becuase if I let it go it will produce tasty berries. I've removed the deadheads completely from potted plants since I lost a hibiscus to mold that was growing in the flower mulch. Outdoors, I normally just let the deadheads fall because something comes along in the night and eats them.
