Below is an arrangement for my Mother-in-Law as a thank you. She prefers white flowers but I did not have enough in bloom so her second choice is peach. The below arrangement is my interpretation of peach (and what I had available for cutting). I chose roses that were just about to open versus fully open so that it had a longer vase life. If they are fully open, they won't live as long. Also, put in spirea, bougainvillea, and split leaf philodendron.
If I know I am going to cut flowers, I make sure they are watered. Yesterday, it rained so that took care of the watering. I, typically, cut the flowers in the evening. Try to do it in the morning or the evening, I believe one time of the day has more sugar and the other time, the flowers have more water.
I cut the flowers at an angle. I, usually, put a can of Mountain Dew in the container. I try to make sure there are no leaves inside the fluid of the vase because I think it causes fungus or bacteria or something. I, also, like the color of Mountain Dew. If I don't want it to be green, I use Sprite. DO NOT USE DIET SODA. I made that mistake only once. But the sugared sodas have citric acid and sugar and a bunch of other stuff that prolongs vase life.
I, then, condition the flowers (or at least that is what I believe I am doing). Ideally, you want to put them in the fridge overnight. In this case the arrangement was too big. So I put them in a dark bathroom. I am certain there are books on the subject but I know you want to keep them in a dark cool place after cutting. Preferably, overnight.
Now, how did I transport them in my car? I usually use a bucket. In this case a five gallon bucket and I put a garbage bag in it.
This can be placed in a seat and belted.
I put the arrangement in the bucket, but how do you keep it from bouncing around in the bucket.
I usually use left over styrofoam. You can use most things of bulk but this has been the most convenient Remember not to leave them in the heat (ie run the AC) because like most things a hot car will kill anything.