I bought a Forsythia branch at my local market 5 days ago. I have it in a tall vase with room temperature water but it has already started to dry out and all the flowers and leaves have all fell off! Why did this happen and can I revive it? :-(
If you didn't change the water, it is possible that some fungi have multiplied enough to kill the plant. Your only chance of reviving the plant is to cut and discard the part that stayed in water and plant the top part in humid/moist soil. Make sure the soil is not too wet, otherwise fungi will rapidly take over. This way, your plant will grow roots if it is not dead by now.