Houston, TX

Houston's gardening calendar is ruled by length rather than cold. The zone 9b designation marks winter lows around 25 to 30°F, but these extremes occur rarely. The last spring frost arrives as late as February 13, and the first fall frost doesn't appear until December 9. That span represents a 300-day growing season, the longest practical window across most of the continental United States.

The actual constraint is heat and humidity. Summers in Houston are hot and relentlessly wet. Figs, Asian persimmons, pomegranates, and jujubes thrive because they're evolved for exactly this climate. Tomatoes and peppers grow well if heat-tolerant varieties are chosen. Many temperate-zone fruits struggle not from cold but from the stress of months above 90°F coupled with high humidity.

This long growing season is deceptive. Spring crops planted in January can mature by May, but summer planting faces the midsummer heat wall. Fall planting windows are generous. A vegetable garden that starts in August or September can run from October through December and into January.

The humidity advantage is disease pressure. Powdery mildew, fungal leaf spots, and root rot are endemic in warm, wet climates. Variety selection for disease resistance is more critical here than winter cold hardiness. Soil drainage and air circulation around plants matter more than frost protection.

The most frequent defeat comes from underestimating February and early March freeze risk. A typical Houston winter is mild, but the last frost date of February 13 is a reminder that late-season cold snaps occur. Tender tropicals planted too early (January) or spring growth forced by warm spells in late January can be caught by sudden freezes. Early-budding crops like Asian persimmons, pomegranates, and figs are especially vulnerable.

Humidity-driven fungal disease is constant. Tomatoes often succumb to early blight or late blight in summer. Squashes and cucurbits develop powdery mildew. Figs get leaf rust. High humidity also traps moisture on foliage overnight, creating conditions fungi exploit.

Heat stress in July and August shuts down many cool-season crops entirely. Lettuce, peas, and brassicas cannot survive this period. Peppers and okra tolerate heat, but inconsistent watering during dry spells stops fruit set.

Mid-March is the safer planting window for frost-sensitive crops. February 13 is the statistical last frost date, but the margin for error is thin. Killing frosts occasionally occur into early April. Waiting a week past mid-March reduces risk to frost-sensitive trees and tender plants.

The long fall season is more productive than spring. May through mid-September is difficult for heat-sensitive crops. August planting of tomatoes, peppers, and herbs allows a full productive fall through December. Fall harvests tend to be more reliable than spring harvests.

Disease-resistant varieties are baseline, not optional, in Houston's humidity. Powdery-mildew-tolerant squash, early-blight-resistant tomatoes, and rust-resistant figs are essential choices. Humid conditions make disease resistance a primary selection criterion.