Five peonies: the vase decides how this bunch looks
A small count is judged almost entirely by what it stands in. Five heavy heads on straight stems have no mass to hold themselves together, so the container does the work that a large bunch does on its own.
Get the neck wrong and the stems splay against the glass within an hour.
What the neck has to do
A peony stem is thick, hollow and fairly rigid, and it does not bend to sit neatly against a wall of glass. Five of them need a neck narrow enough to gather the stems at one point, which keeps the heads over the centre of the vase rather than hanging off the rim.
Too wide, and the bunch collapses outwards into a flat ring of heads.
Too narrow is the other failure, and it is the more common one. Peony stems are broad, the cut ends need water reaching them from all sides, and five crammed into a slim neck press against each other, seal off the flow and start drinking unevenly. A neck that takes the gathered stems with a little slack around them is the working answer.
Height and balance
Set the vase against the stems before cutting anything. The rule florists use is that the heads should sit roughly a third above the rim, which puts the weight low enough that a knocked table does not tip the lot over.
Peony heads are top-heavy once open, and a tall slender vase with a small base is the shape that goes over, whereas weighted glass or stoneware with a broad foot handles the same bunch without incident.
Cut the stems to the vase rather than buying a vase for the stems. Most people do the opposite and end up with five stems standing far too high, heads waving above a narrow column.
How much space it takes up
Very little on the day it arrives, and noticeably more by the third. Peonies open outwards, and five closed buds that fitted a corner of a desk become five broad bowls that need clearance on all sides. Leave room behind the vase as well as in front of it.
A dining table is the obvious place and usually the wrong one. Guests look over a bunch of this size rather than around it, which is fine, but any table in daily use means the vase gets moved several times a day, and every move loosens the gathered stems.
A hall console, a bedside table, a kitchen shelf away from the hob: any of these hold the bunch without it being handled. Five peonies read well in a small room precisely because they do not compete with anything else on the surface. A mirror behind the vase doubles the heads and costs nothing.
Before the courier leaves
If the bunch is going to somebody else, it is worth knowing whether they own a vase at all. Plenty of homes do not, and a small bunch delivered to a flat in Prague with no container ends up in a saucepan or, worse, in its wrapping on a windowsill until the evening. Students, people who have just moved and anyone living out of a suitcase all fall into that group. A jug does the job perfectly well, provided the stems are gathered at the neck. What does not work is a wide bowl, where the heads slide apart and float outwards. Ask, if you can do so without spoiling the surprise.
Ask for the bunch to be delivered with water at the cut ends and, if you can, add a plain glass vessel to the order.
That single question saves more small bunches than any advice about the water itself. Everything else about a bunch this size follows from where it stands.