The Phoenix “False Spring” Trap: Why Your Garden is at Risk in January and February

In the low desert of Phoenix, “see-saw” temperatures in January and February—swinging between the low 60s and high 70s, or even low 80s—create a phenomenon often called a False Spring. While these temperatures feel pleasant to residents, they send conflicting signals to plants that can disrupt their health.

1. How it Affects Plant Life

The primary issue is the disruption of dormancy.

• Premature Growth: Highs in the 70s signal to many plants that winter is over. They begin to “wake up” by pushing out tender new buds and leaves.
• Energy Depletion: Plants use stored energy (carbohydrates) to create this new growth. If temperatures then drop back into the 60s (with corresponding cold nights in the 30s or 40s), the plant may stall or the new growth may be “burned” by cold air, wasting the energy it just spent.
• Sap Flow Issues: Warm days cause sap to flow more freely. If a sudden cold snap follows, the rapid contraction can occasionally lead to sunscald or bark splitting on young trees, especially on the south and west-facing sides.

“Caretaker Landscape manages these wild temperature swings by assuring irrigation systems are fine–tuned to avoid overwatering, and to hold off on the renovation pruning plants, if necessary, to preserve the flowering capabilities of those plants, for when true spring arrives.” said TJ Kelly, East Valley Branch Manager at Caretaker Landscape and Tree Management. “This helps with False Spring blooming and gives the plant a chance to come back with healthy, robust growth.”

2. Impact on the Spring Growing Cycle

The see-saw effect essentially “tricks” the plant into an early cycle that it cannot sustain.

• Poor Bloom Set: For flowering shrubs, the 70-degree weeks can trigger early blooming. If a late frost occurs in February or March (a common occurrence in Phoenix), those blossoms will die, and the plant will not produce flowers for the rest of the season.
• Root Stunting: If a plant focuses its energy on new top-growth during a warm week, it may neglect root development. When the “real” Phoenix heat arrives in May, the plant is left with a weak root system and a large canopy of leaves to support, leading to faster wilting.

3. How to Mitigate Damage

You can’t control the weather, but you can buffer your plants against these swings:

• Hold Off on Pruning: This is the most important step. Pruning stimulates new growth. Wait until at least mid-February or early March to prune frost-sensitive plants. The “ugly” dead branches from earlier in the winter actually act as an insulation layer for the living heart of the plant.
• Do Not Fertilize Yet: Fertilizing (especially with nitrogen) tells the plant to grow. Avoid feeding your landscape until the “see-saw” stops and temperatures are consistently warm.
• Maintain Deep Watering: Keep the soil moist (but not soggy). Moist soil acts as a heat sink, absorbing warmth during the day and radiating it back to the plant at night, which stabilizes the temperature around the roots.
• Mulching: Apply a 2–3 inch layer of organic mulch around the base of plants. This acts like a thermos for the soil, keeping the root zone at a more constant temperature regardless of the air’s fluctuations.

4 Common Phoenix Plants Affected by Temperature Swings