Deciduous, Edible fruit, Trees
For walnut species grown mainly as landscape trees producing bonus crops of nuts, see Juglans. The species described here, English walnut (J. regia), is a widely grown orchard plant native to southeast Europe, southwest Asia; its nuts are the familiar ones sold commercially.
The species is hardy to –5°F (–21°C), but certain varieties are injured by late and early frosts. Reaches 60 ft. tall and wide; grows fast, especially when young. Trunk and heavy, horizontal or upward-angled branches have smooth gray bark; leaves have five to seven (rarely more) 3–6-in.-long leaflets. Walnut husks open in fall, dropping nuts to ground; to hasten drop, knock nuts from tree. Gather fallen nuts immediately, remove any adhering husks, and dry in single layer in airy shade until kernels are brittle (crack a nut open to test); then store. A single tree may bear as much as 100 to 150 lbs. of nuts.
In Zones 1–3, grow walnuts described as Carpathian or Hardy Persian. Varieties include ‘Ambassador’, ‘Cascade’, ‘Chopaka’, ‘Hansen’, ‘Russian’, and ‘Somers’; these range in hardiness from –25°F (–32°C) to –35°F (–37°C). Here are best choices for other zones. In Zones 4–7, ‘Chambers’, ‘Cooke’s Giant Sweet’, ‘Franquette’, and ‘Spurgeon’ bloom late enough to escape spring frosts, yield high-quality nuts. In Zones 8, 9, grow ‘Carmelo’, ‘Chandler’, ‘Cooke’s Giant Sweet’, ‘Hartley’, ‘Idaho’, ‘Payne’, ‘Pedro’, or ‘Serr’. In Zones 14–16 and warm parts of 17, try ‘Carmelo’, ‘Chandler’, ‘Cooke’s Giant Sweet’, ‘Franquette’, ‘Hartley’, ‘Payne’, ‘Pedro’, and ‘Serr’. In Zones 18–20, grow ‘Payne’, ‘Pedro’, or ‘Placentia’. In Zones 21–23, ‘Pedro’ and ‘Placentia’ are best choices.
Plant English walnut as a landscape tree only on large lots. It’s out of leaf a long time, messy in leaf (honeydew drip and sooty mold due to aphid infestations), and messy in fruit (husks can stain). Many people are allergic to the wind-borne pollen. Plant bare-root walnuts as soon as they are available in winter or early spring. Choose an open planting location in full sun. In cold winter areas, grow on a slope to minimize frost damage. Most English walnuts are partially self-fruitful but bear better with a pollenizer. Grow in deep soil. Established plants survive with no supplemental moisture but need deep watering for top-quality nuts. Keep other plants beyond the drip line, where feeder roots grow. Fertilize only if your tree is putting out less than 18 in. of new growth per year. Train young trees to a central leader; mature ones need pruning only to remove dead wood or correct shape.
In addition to aphids, pests include scale, codling moths, and spider mites. Walnut husk fly attacks husks, causing them to turn black and adhere to shell. Husks are difficult to remove and the shell is stained, but the nutmeats are not damaged. In many agricultural areas, such as California’s San Joaquin and Sacramento Valleys, new subdivisions are often built in old walnut groves, leaving the trees behind as landscape specimens. These tree often decline quickly due to increased watering or soil compaction.
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