The Lamb Hass avocado is a cultivar of Persea americana, part of the Lauraceae family, which includes species like bay laurel and cinnamon. Botanically, it’s a berry, characterized by its single large seed and fleshy pulp, though it’s typically used as a vegetable in culinary applications. Lamb Hass is a hybrid derived from the Hass variety, with predominantly Guatemalan ancestry (around 85-90%) and a minor Mexican influence, inherited through Hass’s lineage. This Guatemalan dominance contributes to its rich, oily flesh and robust skin, while the Mexican trace enhances its adaptability, making it a refined evolution of its famous parent.
Originating in California, the Lamb Hass avocado was developed by Robert Lamb and his sons at their Camarillo nursery in Ventura County. In the late 1970s, they selected it from seedlings of a Hass tree pollinated by an unknown variety, likely a Type B like Bacon or Fuerte, aiming for a late-season alternative. After years of testing, it was patented in 1996 by the University of California, which promoted it for its upright growth, higher yield, and extended harvest window. Though not as widespread as Hass, Lamb Hass has gained traction among growers for its productivity and quality.
Identifying a Lamb Hass avocado mirrors its Hass heritage with a twist. It’s pear-shaped to oval, slightly larger than Hass, weighing 10 to 18 ounces (280-510 grams). Its skin is thick, pebbly, and green when unripe, turning dark purple-black when ripe—nearly identical to Hass but often glossier. The flesh is creamy, golden-green, with a high oil content (around 19-23%), encasing a medium seed that leaves ample edible yield. Its thicker skin and denser texture set it apart, offering a premium feel over its progenitor.
Lamb Hass avocados thrive in USDA Hardiness Zones 9 to 11, suited to warm, subtropical climates with minimal frost risk. They’re slightly less cold-tolerant than Mexican varieties, handling brief dips to 28°F (-2°C), but prolonged cold damages blossoms and fruit. Coastal California, particularly Ventura and Santa Barbara Counties, provides ideal conditions—well-drained soils, full sun, and moderate winds. Its Guatemalan roots make it sensitive to overwatering, though it’s hardier than pure Guatemalan types due to its hybrid vigor.
Seasonality for Lamb Hass extends from June to October in California, peaking in late summer to early fall, later than traditional Hass (April-September). This extended window, enabled by its slower maturation, fills a gap when Hass supply wanes, with fruit harvested mature but firm and ripened off-tree. Its thick skin allows longer on-tree storage than thinner-skinned varieties, boosting flexibility. While Hass dominates year-round via imports, Lamb Hass shines locally during its season, available at farmers’ markets and specialty stores.
Culinary uses of Lamb Hass avocados mirror Hass but amplify its richness. It’s perfect for guacamole, where its creamy, nutty flesh blends seamlessly with lime and spices, holding texture in chunkier mixes. Sliced or cubed, it elevates salads, sandwiches, or sushi, pairing with bold flavors like soy or citrus. Its high oil content makes it ideal for spreads on toast or blending into dressings, offering a luxurious mouthfeel. Best raw—cooking risks bitterness—it also suits creative dishes like avocado fries or cold soups, making it a versatile, late-season star for avocado aficionados.
Cultivation of Lamb Hass Avocado
Climate Requirements
Lamb Hass avocados flourish in USDA Hardiness Zones 9 to 11, thriving in warm, subtropical climates with temperatures between 65°F and 85°F (18°C to 29°C). Their Guatemalan dominance limits cold tolerance to brief drops around 28°F (-2°C), with frost harming blossoms and young trees. Growers in California’s coastal regions use wind machines or sprinklers during rare cold snaps to protect crops.
Soil Preferences
Well-drained soil is essential, as Lamb Hass is prone to root rot (Phytophthora cinnamomi). Sandy loam or volcanic soils with a pH of 6.0 to 6.5 promote aeration and water flow, ideal for its shallow roots. Clay soils require raised beds or organic amendments (e.g., compost) to prevent saturation. Soil testing ensures drainage and nutrient balance before planting.
Site Selection
Flat or gently sloping land (up to 10% grade) aids drainage, while full sun—6-8 hours daily—drives fruit production. Wind protection (natural ridges or planted barriers) shields its heavy, late-season fruit from damage. Coastal California sites, like Ventura County, offer the stable warmth and moderate humidity Lamb Hass prefers over inland extremes.
Tree Propagation
Lamb Hass is propagated by grafting onto vigorous rootstocks like ‘Toro Canyon’ or ‘Duke 7’ to ensure disease resistance and maintain its upright, productive traits. Seeds won’t produce true Lamb Hass fruit due to its hybrid origins, so nursery grafts—scions from certified trees—are grown for 12-18 months before transplanting. This preserves its late-season quality.
Planting
Trees are spaced 15-20 feet (4.5-6 meters) apart, though its upright growth allows tighter spacing (12-15 feet) with pruning. Spring planting, post-frost, is optimal in California, giving roots time to establish before summer heat. Holes twice the root ball’s size are enriched with compost, and stakes support young trees against wind until rooted.
Irrigation
Lamb Hass requires moderate, precise watering—20-40 gallons (75-150 liters) per tree weekly, adjusted for rainfall and soil type. Drip irrigation targets the root zone, avoiding overwatering that its Guatemalan roots dislike. Young trees need 2-3 weekly sessions, tapering as they mature. Soil moisture sensors balance hydration with drainage to prevent rot.
Fertilization
Nitrogen is applied at 1-2 pounds (0.45-0.9 kg) per tree yearly, split into spring and midsummer doses to fuel its high yield. Zinc and potassium supplements address deficiencies, often via foliar sprays in sandy soils. Organic mulch or balanced fertilizers (e.g., 10-10-10 NPK) sustain health, but over-fertilizing risks vigor over fruit, so leaf analysis refines inputs.
Pollination
Lamb Hass is a Type A flowerer—female in the morning, male the next afternoon—self-fertile but benefiting from cross-pollination. Pairing with Type B varieties like ‘Bacon’ or ‘Zutano’ boosts fruit set, as bees bridge bloom overlaps (April-June in California). Orchards often introduce hives to maximize pollination, enhancing its late-season output.
Pruning
Light pruning shapes Lamb Hass’s upright canopy, removing dead wood or crowded branches to improve light and airflow. Young trees are trained into a narrow, open form over 2-3 years, while mature trees get annual thinning post-harvest (fall) to manage fruit load. Its compact growth reduces heavy pruning needs, supporting its high productivity.
Pest and Disease Management
Persea mites and thrips are key pests, controlled with predatory insects (e.g., lacewings) or targeted sprays like sulfur. Root rot is the main disease, countered with resistant rootstocks and strict irrigation control. Regular scouting and debris removal limit pest spread, favoring integrated pest management over broad chemicals.
Fruit Development
After pollination, Lamb Hass fruit matures over 12-14 months, ready for harvest from June to October in California. It ripens off-tree, with dry matter content (22% minimum) signaling maturity. Fruit weighs 10-18 ounces (280-510 grams), with size tied to water, nutrients, and thinning—its heavy yield may require branch support.
Harvesting
Lamb Hass is picked mature but firm, with clippers snipping stems to preserve thick skin. Timing aligns with oil content tests, peaking in late summer to fall for market demand. Workers use ladders for its taller, upright form, collecting into padded bins to avoid bruising its dense fruit, a plus over thinner-skinned types.
Post-Harvest Care
Harvested fruit is cooled to 40-50°F (4-10°C) to slow ripening, then graded for size and quality. Ripening occurs off-tree at 65-75°F (18-24°C) over 7-14 days, or hastened with ethylene commercially. Thick skin extends shelf life over thin-skinned varieties, but timely handling maximizes freshness. Mature trees yield 150-250 pounds (68-113 kg) annually, reflecting its breeding for abundance.