Tucson, AZ

Tucson's gardening calendar is defined by extremes: a mild winter that rarely dips below 25°F, a spring frost date of February 5, and a first fall frost not until December 9. That 307-day growing season is among the longest in the continental United States. The constraint is not cold but heat and water. Summer temperatures regularly exceed 110°F, and annual rainfall averages 12 inches.

This climate favors Mediterranean and subtropical crops that thrive on neglect. Figs, pomegranates, and Asian persimmons excel in Tucson's conditions and reward minimal water. Jujubes and goji berries, less common nationwide, reliably produce here. Even annual heat-tolerant crops like sweet and hot peppers can mature two or three cycles per season if managed for succession planting.

The early spring frost date (February 5) creates a deceptive risk window. Tender new growth on deciduous trees can be caught if an unexpected freeze follows warm February weather. This is less a hard freeze than a desiccating event, especially dangerous for newly transplanted trees or early bloomers.

Tucson gardeners work within a water-constrained budget. Well-established xerophytic plants and deep mulch reduce the penalty of the desert climate, but annuals and perennials requiring consistent moisture demand irrigation most of the year. The trade-off is straightforward: species adapted to the Sonoran Desert thrive with minimal input; non-adapted plants consume water and attract stress.

The February 5 spring frost arrives early enough to threaten tender new growth if warm spells precede it. Trees leafing out in late January face sudden defoliation.

Summer heat above 110°F causes blossom drop on fruit crops, sunscald on exposed fruit, and accelerated pest cycles. Spider mites, whiteflies, and root-knot nematodes thrive in hot, sandy soil. Water stress compounds these problems. Trees installed in March often fail to establish if summer arrives before their root systems deepen.

Desert soil is typically neutral to slightly alkaline (pH 7.5 to 8.5) and low in organic matter. Standard soil amendments wash through quickly in the sparse rainfall. Compost amendments help but require reapplication every 1 to 2 years. Micronutrient deficiencies, particularly iron, show up in new growth.

Choose heat-adapted varieties. Figs and pomegranates yield reliably. Standard peach and apple varieties developed for humid regions often abort fruit in Tucson's dry heat; seek regional trial results before planting. Asian persimmons, in particular, produce heavily if sited in afternoon shade in summer.

Protect against the February frost. Hold off spring pruning until mid-February. If frost threatens and trees have leafed out, irrigation the evening before can reduce desiccation damage. Avoid the temptation to plant tender material before March 1.

Mulch heavily and water infrequently but deeply. A 4-inch mulch layer over 3 to 4 feet radius around the base reduces water need and moderates soil temperature during peak summer. Water fewer times per week but saturate the root zone. This encourages deeper roots.