Conditioning is the process of preparing freshly cut stems to maximize water uptake and vase life. Different flowers need different conditioning methods.
This works for most flowers: re-cut stems at a 45-degree angle under water, strip all foliage that would be below the waterline, place in a clean vase with room-temperature water and floral preservative, and let hydrate in a cool spot for 2–4 hours before arranging. Applies to zinnias, cosmos, celosia, snapdragons, rudbeckia, and most others.
For flowers that wilt easily or have woody stems: dip the bottom 1–2 inches of the stem in near-boiling water for 5–10 seconds, then transfer immediately to cool water. This forces air out of the stem cells and improves water uptake. Use for dahlias, stock, and any flower that wilts despite being freshly cut.
Daffodils: Must be conditioned alone for 12–24 hours. Their sap harms other flowers. Do not re-cut after conditioning or the sap will flow again.
Tulips: Prefer cool, shallow water. Wrap loosely in paper during initial conditioning to keep stems straight.
Basil: Use room-temperature water, not cold. Cold water blackens the leaves.
Peonies: Can be dry-stored in a refrigerator for weeks in tight bud, then opened by placing in warm water.
Commercial preservative packets contain sugar (food), citric acid (lowers water pH), and bleach (prevents bacterial growth). You can make a basic version: 1 teaspoon sugar, 1 teaspoon bleach, and 2 teaspoons lemon juice per quart of water. Change water and re-cut stems every 2–3 days for maximum vase life.