Arranging daffodils in a vase combined with other flowers will make those flowers wilt, even though the vase has plenty of water. Unfortunately daffodil sap (and that of many other Amaryllidaceae plants) introduces both bacteria and toxic alkaloids into the vase water that causes grief to many cut flowers, including tulips and also roses.
You’ve probably noticed that when you cut a daffodil stem, it weeps a thick and sticky sap, or mucilage. Bacteria thrive on this mucilage in the vase water, blocking some plants like roses from being able to draw water up their stems, so they start to wilt. For tulips sharing a vase with daffodils, the alkaloids in the mucilage can cause them to wilt.
If you recut stems on bought daffodils, or you’ve picked them fresh from your garden, you’ll need to stand them in a separate vase of water for several hours before combining them with other spring-flowering beauties.
Another tip for cutting your daffodils for vase display – although you can cut them as soon as they display a ‘gooseneck’ (their typical nodding form), and this is how commercial growers often harvest them for easier shipping, the blooms will last longer in the vase if they are picked as soon as they’re fully open.