Leaving flowers in a car is generally a bad idea, and for anything more than a few minutes, it's a fast way to ruin them. The primary culprit is the car's interior temperature, which can skyrocket to dangerous levels far beyond the outside air. This heat, combined with a lack of water, causes flowers to wilt, dehydrate, and die rapidly. Even on a mild 72°F (22°C) day, the temperature inside a parked car can reach 116°F (47°C) within an hour, creating an oven-like environment that is devastating to most cut flowers.
The science behind this is the greenhouse effect. Sunlight passes through the windows, and the upholstery, dashboard, and seats absorb the energy, radiating it back as heat that becomes trapped inside. This extreme heat accelerates moisture loss through the petals and leaves (a process called transpiration) much faster than the stem can draw up water. The result is a limp, dried-out bouquet.
Some flowers are more resilient than others. Hardy blooms like alstroemeria or chrysanthemums may last a bit longer, while delicate roses or tulips are exceptionally vulnerable. If you must leave flowers in the car, absolute best practices are crucial. Park in a shaded garage, never in direct sun. In summer, consider using a sunshade for the windshield. For very short stops, placing them in the trunk can be slightly better than the passenger cabin, as it's darker, but the trunk still heats up significantly and is not a long-term solution.
The bottom line is to treat your car as a temporary transport vehicle, not a storage unit. The safest approach is to make the flower delivery or errand your final stop before heading directly home.
| External Temperature | Estimated Interior Car Temperature After 30 Minutes | Likely Effect on Cut Flowers |
|---|
| 70°F (21°C) | 104°F (40°C) | High Risk of Wilting: Accelerated dehydration begins. |
| 80°F (27°C) | 114°F (46°C) | Severe Damage Likely: Rapid wilting and petal scorch. |
| 90°F (32°C) | 124°F (51°C) | Critical Damage: Flowers cook; irreversible damage in minutes. |
| 100°F (38°C) | 134°F (57°C) | Fatal: Extreme heat will destroy most bouquets almost instantly. |
