Raintree Growing Guide
Walnuts
A long-lived, magnificent tree that rewards patience with decades of high-quality nuts, exceptional timber value, and handsome landscape presence. Site selection, variety, and the juglone question — explained.
AT A GLANCE
SUN
Full sun — minimum 8 hours/day; shade-intolerant
USDA ZONES
5–9 most varieties; Carpathian types to Zone 4
Chill Hours
~700–1,000 hrs; Franquette higher; Carpathian variable
Growing difficulty
Difficult — large mature size; long time to bear
Pollination
Self-fertile; a second variety greatly improves yield
First Nuts
Grafted: 4–7 yrs · Full production: 10–15 yrs
Soil
Deep (6+ ft), well-drained; pH 6.0–7.0; no wet soils
Mature Size
40–60 ft tall; 35–50 ft spread — plan for the long term
Lifespan
200–300 years; a multi-generational planting
Why grow a walnut?
The walnut (Juglans regia) — known variously as English walnut, Persian walnut, or common walnut — is one of the oldest cultivated nut trees in the world, with a history of cultivation spanning over 4,000 years. Native to the mountains of Central Asia, it spread through Persia to Greece and Rome and arrived in the Americas with early European settlers. California now produces approximately 99% of the United States commercial walnut crop (Oregon State University; NC State Extension), but home and small-orchard growers across much of the country can produce excellent walnuts with the right variety selection.
A walnut tree is a long-term investment. Grafted trees begin producing in 4–7 years and reach full production after 10–15 years. A well-sited tree can yield 100 pounds or more of nuts annually at maturity and live for several centuries. Beyond the nut crop, the tree is a landscape asset: large, graceful compound leaves, handsome winter silhouette, and wood that is among the most valuable of any temperate species.
Walnuts are the complete home orchard tree — they ask for patience in return for a lifetime of high-quality, highly nutritious nuts that are genuinely superior to anything available commercially. The fresher the walnut, the more pronounced the sweetness; a nut eaten the day it comes out of the shell bears little resemblance to a walnut that has spent months in commercial storage.
⚠ State shipping restrictions — check before ordering
USDA regulations prohibit shipping Juglans species to the following states: Arkansas, Arizona, California, Indiana, Kansas, Michigan, Minnesota, Missouri, Nebraska, Ohio, Oklahoma, Texas, and Wisconsin. These quarantines exist to prevent the spread of the Walnut Twig Beetle (Pityophthorus juglandis) and Thousand Cankers Disease — a lethal combination of that beetle and the fungal pathogen Geosmithia morbida that has caused widespread mortality in black walnut and can affect English walnut as well. Raintree complies with all USDA and state regulations and cannot ship walnut trees to restricted states. Some individual variety listings may show slight variations — always verify on the specific product page. If you live in a restricted state, contact your state Department of Agriculture for guidance on locally sourced, certified nursery stock.
Washington, Oregon, and Idaho are not restricted — Raintree ships walnuts freely to PNW customers.
Choosing varieties
The most important distinction in English/Persian walnut variety selection is between California-type varieties (Chandler, Hartley, Howard — suited to mild winters and long, warm summers) and Carpathian-type varieties (Franquette, Ambassador, and various Carpathian selections — suited to colder winters and the shorter summers of the Pacific Northwest and higher elevations).
A critical practical note from OSU Extension: late-leafing varieties are strongly preferred in frost-prone areas. Walnuts are injured by spring frosts far more frequently than by winter cold. Varieties that leaf out early — including most California types — are regularly damaged by late spring frosts in the PNW and colder climates. Varieties like Franquette that leaf out late escape most frost damage.
Always purchase grafted trees for nut production. Seedling walnuts are genetically variable, fruit quality is unknown, and they take significantly longer to bear — 5–8 years or more. Grafted trees from named cultivars produce reliably and fruit 1–3 years earlier.
| Variety | Type | Zones | Notes |
|---|---|---|---|
| Franquette PNW | English/Carpathian | 5–9 | The standard PNW walnut variety and one of the best choices for frost-prone sites anywhere. Late leafing out avoids spring frost damage. Large, well-flavored nuts; excellent for fresh eating, drying, and baking. Recommended by OSU Extension for Oregon and western WA. Also an excellent pollinizer for Chandler. Moderate yield; large tree. Bears on terminal and lateral buds. |
| Chandler | English (California) | 6–9 | The world's most widely planted commercial walnut. Light-colored kernels, thin shell, outstanding quality — considered the best-tasting walnut by most tasters (University of California Davis breeding program). Very high yield. Bears primarily on lateral buds. Best suited to mild-winter, long-season climates. Self-fertile but yields significantly higher with a pollinizer (Franquette, Cisco). Not recommended for areas with regular late spring frosts. |
| Hartley | English (California) | 6–9 | A California variety with a long commercial history; large nuts with good quality. Leafs out 10–14 days before Franquette — susceptible to spring frost damage (OSU Extension). Moderate producer; tends toward weak crotches and drooping limbs. Not recommended for frost-prone Oregon or WA sites. Franquette is a good pollinizer. Best in warmer, frost-free locations. |
| Ambassador Carpathian Cold Hardy | Carpathian | 4–8 | Fast-growing Carpathian selection with good cold hardiness. Excellent choice for Zone 5 and colder Zone 6 sites or high-elevation plantings where California types would be frost-damaged regularly. Carpathian types are native to the Carpathian Mountains of Eastern Europe and are the right choice east of the Cascades (OSU Extension; USU Extension). |
| Cascade PNW | Carpathian | 4–8 | A Pacific Northwest Carpathian selection with improved cold hardiness. Well-suited to eastern WA, eastern OR, and higher-elevation western sites. Good nut quality; reliable producer in cool climates. |
| Howard | English (California) | 6–9 | California variety with lateral bearing habit; high production and good nut quality. Leafs out at about the same time as Franquette. Franquette can serve as pollinizer. Best in warmer sites with long growing seasons; less suited to frost-prone areas than Franquette. |
⚠ Pollination — self-fertile but a pollinizer matters
All walnut varieties are technically self-fertile — they will produce nuts without a second tree, provided pollination timing works out (OSU Extension). However, protandry and protogyny (the catkins and female flowers often maturing at different times on the same tree) means self-pollination can be poor in some years and climates. A second variety that sheds pollen during the peak female receptivity of the main variety significantly improves yield and nut size. Franquette is an excellent pollinizer for Chandler, Howard, and Hartley. Wind carries walnut pollen; trees should be within 200 feet for reliable cross-pollination.
Pacific Northwest tip
OSU Extension's walnut guide is explicit on variety selection for Oregon: Franquette is the standard recommendation; Hartley is generally not cold-hardy enough for Oregon except on frost-free hillsides; Carpathian types are the right choice east of the Cascades. For the Willamette Valley and western Washington lowlands, Franquette or Howard with Franquette as pollinizer performs best. Spring frosts are a far more frequent cause of crop loss in the PNW than winter cold — late-leafing varieties are not optional, they are essential.
Juglone — the garden planning question
Walnuts produce a chemical called juglone (5-hydroxy-1,4-naphthalenedione) in their leaves, husks, bark, and roots. When juglone enters the soil, it can inhibit respiration in sensitive plants — causing yellowing, wilting, and death. This phenomenon, known as allelopathy, has been known since Roman times (Purdue Extension; Illinois Extension; WSU Extension).
Two important clarifications before planning your garden around a walnut:
First: English/Persian walnut produces significantly less juglone than black walnut. The allelopathy concern is primarily associated with black walnut (Juglans nigra). English walnut (J. regia) also produces juglone but at considerably lower concentrations — it is far less problematic than its reputation suggests (Virginia Tech Extension; PSU Extension). Sensitive plants may still be affected within the drip line, but the zone of concern is smaller.
Second: not all plants are sensitive. Many common garden plants grow happily near English walnuts. The most sensitive plants are in the Solanaceae family and certain ornamentals.
Sensitive to juglone — plan carefully
Fruit trees & berries: Apple, pear, blackberry, blueberry, domestic grape, strawberry (in heavy concentrations).Vegetables: Tomatoes, peppers, eggplant, potatoes (all Solanaceae).Ornamentals: Rhododendron, azalea, mountain laurel, blueberry, chrysanthemum, lily-of-the-valley, peony, lilac. Keep these outside the drip-line zone and preferably well away from the root spread.
Tolerant — generally fine near walnuts
Fruit trees & berries: Cherry, plum, peach, nectarine, black raspberry, pawpaw, persimmon, elderberry, quince, serviceberry. Vegetables: Carrots, corn, beets, beans, squash, onions, garlic. Ornamentals: Most grasses and turf, catalpa, oak, black locust, forsythia, violets, hostas, astilbe, most ferns.
⚠ Important context for fruit tree and berry planning
For Raintree customers planning a mixed home orchard, the juglone sensitivity of apple, pear, blueberry, blackberry, and grape is worth taking seriously. Blueberries in particular — already demanding in their soil requirements — are one of the more consistently documented sensitive plants (Purdue Extension; K-State Extension). Apples and pears are also on the sensitive list. Cherries, plums, peaches, pawpaws, and persimmons, by contrast, are generally observed as tolerant and can coexist near walnuts.
Two important caveats: first, these lists are based overwhelmingly on black walnut (J. nigra), which produces significantly more juglone than English/Persian walnut (J. regia). The risk from English walnut is real but meaningfully lower — sensitive plants are most at risk within the drip line where root density and juglone concentration are highest. Second, many problems blamed on juglone are actually caused by competition for light, water, and nutrients under a large tree canopy — factors that affect all nearby plantings regardless of species (Iowa State University Extension; WSU Extension).
Practical guidance from PSU Extension and UNH Extension: locate vegetable gardens and sensitive fruit plantings (especially blueberries and apples) well away from walnut trees; use raised beds lined with weed fabric to reduce root contact if gardening nearby; do not use walnut leaves, hulls, or wood chips as mulch around sensitive plants; improve soil drainage with organic matter to encourage microbial breakdown of juglone. Juglone breaks down in well-aerated, biologically active soil relatively quickly — compacted or poorly drained soils retain it longer.
Site selection and soil
Site selection is critical — walnuts are long-lived, deep-rooted, and large. The right choice upfront avoids problems that would take decades to correct.
Sun
Walnuts require full sun and are shade-intolerant (NC State Extension). A minimum of 8 hours of direct sun daily is needed for good nut production. Shade significantly reduces yield and increases disease susceptibility.
Soil depth — the critical factor
Walnut taproots can extend 10 feet or more into the ground. Soil must be deep — at least 6 feet of well-drained soil is the minimum (OSU Extension). Before planting, use an auger or posthole digger to confirm there is no shallow bedrock, hardpan, or seasonally high water table within 6 feet. Shallow soil or impeded drainage is the most common cause of poor walnut establishment and early decline. Walnuts are strictly intolerant of waterlogged conditions.
Soil pH and fertility
A slightly acidic to neutral soil — pH 6.0–7.0 — is ideal. Walnuts prefer moderately fertile, well-drained loam. Avoid heavy clay soils without significant amendment. They tolerate a range of soils better than peaches or blueberries, but they will not thrive in compacted, poorly aerated, or water-holding soils.
Frost-pocket avoidance
Plant on slopes or elevated ground where cold air drains away rather than collects. Spring frost damage to emerging leaves and female flowers is the single most common cause of poor crops in the PNW and colder climates (OSU Extension). Even a slight elevation above a valley floor provides meaningful protection.
Spacing
Plant trees a minimum of 35 feet apart — 40 feet is better for long-term canopy development. Walnuts are vigorous, large trees; crowding reduces yield, light penetration, and airflow. In an orchard row setting, plan 35–40 feet between trees and 40–50 feet between rows.
Planting
Plant grafted trees in early spring while dormant, or in fall in mild-winter climates. Set the graft union 2–3 inches above soil grade. Stake young trees for the first 1–2 years — new walnut wood is soft and susceptible to wind damage. Water deeply at planting and maintain consistent moisture through the first two growing seasons. Keep a 3–4 foot weed-free, mulched circle around the trunk.
Pacific Northwest tip
In the maritime PNW, hillside sites are preferable to valley floors for walnut production — cold air settles in low areas and late-spring frosts are more common there. South-facing hillsides provide both frost drainage and additional warmth for nut development. The deep soils of the Willamette Valley and Umpqua Valley are well-suited to walnut production where frosts are managed. Western WA lowlands produce good crops where late frosts are not frequent; Franquette is the most reliable variety for these sites.
Pruning and training
Walnuts are trained to a central leader or modified central leader system — a strong central trunk with well-spaced scaffold branches radiating outward (USU Extension; Plant Village/PSU). This is different from the open center used for peaches and plums. The central leader approach suits walnut's natural upright growth habit and supports heavy crops on a strong structural framework.
Timing — never prune in spring
This is the most important pruning rule for walnuts: prune in late summer to late fall, or in early winter — never in late winter or spring. Late winter or spring pruning causes heavy sap flow ("bleeding") from cuts, which weakens the tree, is difficult to stop, and invites disease entry (USU Extension). Summer or fall cuts close more cleanly with far less sap flow.
Training young trees
In the first 1–6 years, training focuses on developing a strong central leader with well-spaced scaffold branches. UC Davis research (Hasey, Lampinen) found that young lateral-bearing walnut varieties (Chandler, Howard) do not necessarily require heavy pruning to maintain growth — light minimum pruning is preferable on young trees, which are sensitive to cold and can have wood killed by freezing temperatures. Delay major structural pruning until late summer of the first year at earliest, and prune into mature round wood rather than green soft tissue.
Remove crossing, rubbing, or competing leaders early while the wood is small. Maintain a clear central leader. As the tree matures, focus on removing dead or diseased wood, opening the canopy to light, and keeping the tree at a manageable height — industry guidelines suggest 7–8 feet of height is achievable with consistent management, though home orchard trees grown without commercial ladder access often reach 20–30 feet.
Pacific Northwest tip
In the PNW, the late-summer pruning window (August–September) aligns well with the dry season and avoids the region's wet winters when disease transmission through pruning wounds is highest. The combination of a dry pruning window and the late-summer timing produces the cleanest cuts and lowest disease risk. Avoid any pruning from October through June.
Watering and feeding
Young walnut trees need consistent deep watering while establishing their taproot system — approximately 1 inch per week during the growing season, adjusted for rain. Deep, infrequent irrigation is always preferable; walnut roots follow moisture downward and shallow watering encourages surface rooting that is vulnerable to drought. Once established (typically after 2–3 seasons), walnuts are moderately drought-tolerant, though consistent moisture during the nut-development period (summer) directly improves nut size and fill.
In drier regions and east of the Cascades, permanent drip irrigation is important for production-level yields. OSU Extension notes that a good mature tree in a home site might yield about 100 pounds of nuts annually with controlled watering, but many trees produce only half that without supplemental irrigation during dry summers.
Fertilize modestly. Monitor annual shoot growth — 12–24 inches per year on young trees and 8–12 inches on mature bearing trees indicates adequate nutrition. Apply balanced fertilizer in early spring only. Avoid late-season fertilization. Excessive nitrogen produces lush, soft growth that is susceptible to walnut blight and frost damage. In fertile soils, established trees may need little to no fertilizer.
Pacific Northwest tip
In western WA and OR, spring rainfall typically covers early-season moisture needs. Supplemental irrigation becomes important in July–August during the dry season when nuts are sizing up and filling. In eastern WA and OR, consistent drip irrigation from early summer onward is essential for good yields — the warm, dry summers that suit walnut flavor development also require active moisture management.
Harvest and processing
Walnuts ripen in September–October depending on variety and location. The nuts are ready for harvest when the green outer husk begins to split or separate from the shell. Nuts may fall naturally when ripe; shaking or pole-poling branches brings down the rest. Collect promptly — nuts left on wet ground deteriorate quickly.
Hulling
Remove the green outer husk as soon as possible after harvest. Husks contain tannins and the juglone precursor hydrojuglone — prolonged contact darkens and stains the shell and can impart a bitter, off-flavor to the kernel. Wear gloves during hulling, as the stain is persistent and difficult to remove from skin and clothing. Hulls can be removed by hand, by rolling underfoot on hard pavement, or using a hulling drum for larger volumes.
Washing and curing
After hulling, wash nuts thoroughly to remove husk residue, then cure (dry) in a single layer in a warm, well-ventilated location for 2–4 weeks. Nuts are adequately dried when the kernel rattles in the shell. Properly cured walnuts store well for months in a cool, dry location; refrigeration extends shelf life significantly. Freeze for longest-term storage.
Pacific Northwest tip
In western WA and OR, harvest timing requires attention — fall rains can begin before all nuts have been collected, and nuts left on the wet ground develop mold quickly. Monitor trees closely as September arrives and harvest promptly when hulls begin splitting. Curing must be done in a location with good airflow; our humid falls make it important to keep nuts off the ground and ensure good air circulation during the drying period.
Common problems
Walnuts are relatively low-maintenance compared to most fruit trees, but they have a handful of specific challenges worth understanding before planting.
Spring Frost Damage
High — most common crop loss cause
Late spring frosts kill emerging leaves and female flowers, destroying the year's potential crop. In the PNW, spring frosts are a far more frequent cause of crop failure than winter cold. Even late-leafing varieties like Franquette can be damaged in an unusual late frost, especially in valley floor locations.
- Choose late-leafing varieties — Franquette in the PNW; Carpathian types for colder regions
- Plant on slopes or elevated ground where cold air drains downward, away from the tree
- Avoid valley floors and low spots that collect cold air
- Young trees can be protected with frost cloth on nights when temperatures threaten below 28°F
Walnut Blight
High — PNW
Caused by the bacterium Xanthomonas arboricola pv.juglandis. The primary disease of walnuts in the PNW. Dark, water-soaked spots appear on catkins, leaves, and developing nuts; infected nuts turn black and fall early. Spreads rapidly during cool, wet spring weather — exactly the conditions of the maritime PNW bloom period. OSU Extension identifies walnut blight as the most damaging walnut disease in Oregon.
- Apply copper bactericide at bud burst (early spring) and again at full bloom — timing is critical
- Choose late-leafing varieties, which are exposed to fewer blight-favorable weather periods during leaf out
- Prune for open canopy and airflow to reduce moisture retention in the canopy
- Never prune in wet weather; avoid wetting leaves with overhead irrigation
Pacific Northwest
Walnut blight is the primary reason copper applications are standard practice for PNW walnut growers. Timing the copper spray to bud burst — before the bacteria can infect emerging tissue — is more effective than later applications. Wet springs with frequent rain events require closer monitoring and potentially additional applications per the OSU spray schedule.
Thousand Cankers Disease (TCD)
High — regulatory concern; eastern US
A lethal combination of the Walnut Twig Beetle (Pityophthorus juglandis) and its associated fungal pathogen (Geosmithia morbida). Primary concern is for black walnut in the eastern US, but English walnut can also be affected. This is the primary reason USDA restricts shipping ofJuglansspecies to many states. Trees decline over several years as cumulative canker development girdles branches and eventually the main stem.
- Purchase nursery stock only from reputable sources with proper certification — do not transport walnut material between states without verifying restrictions
- Currently no effective chemical treatment; prevention through quarantine and clean planting stock is the primary defense
- Report suspected infestations to your state Department of Agriculture or USDA APHIS
Walnut Husk Fly
Moderate — western US
The walnut husk fly (Rhagoletis completa) lays eggs in the green husk; larvae tunnel through the husk, causing dark staining and off-flavors in the shell and sometimes the kernel. Primarily a western US pest; significant in California and the Pacific Coast states.
Walnut husk fly — the adult has patterned, banded wings; maggots tunnel the husk and stain the shell. (Shown: Rhagoletis suavis, a walnut husk fly.) Photo: Ryan Hodnett(CC BY-SA 4.0), via Wikimedia Commons — resized.
- Monitor with yellow sticky traps or sphere traps starting in July
- Kaolin clay (Surround) applied as a physical barrier on the outer husk deters egg-laying
- Spinosad-based insecticides are effective when timed to adult fly activity per traps
- Harvest as early as nuts are ripe — hulls infested by the fly should be removed immediately and composted or buried
Codling Moth
Moderate
Codling moth (Cydia pomonella) — primarily known as an apple pest — also attacks walnuts. Larvae enter through the stem end of the nut, damaging the kernel. Present throughout the PNW.
Adult codling moth — note the coppery band at the wingtip. The larvae tunnel into developing fruit. Photo: Ben Sale(CC BY 2.0), via Wikimedia Commons — resized.
- Monitor with pheromone traps; time treatments to flight activity
- Codling moth granulosis virus (Cyd-X) is approved for organic use and effective on walnuts
- Kaolin clay provides some barrier protection on developing nuts
- Good sanitation — collecting fallen nuts promptly — reduces populations
Squirrels and Crows
Moderate — harvest timing
Both squirrels and crows actively harvest walnuts, often before the nuts are fully ripe. Squirrels will cache nuts; crows crack them on hard surfaces. In suburban and semi-rural settings, wildlife competition for the crop can be significant.
- Harvest promptly as nuts begin to fall naturally; don't leave ripe nuts on the tree or ground
- Hardware cloth trunk guards reduce squirrel access on young trees
- Bird netting over smaller trees provides some protection, though it is difficult on large trees
Seasonal care calendar
Winter
Dec - Feb
- This is a good time for minor structural assessment only — do NOT prune in late winter; sap flow will be excessive
- Check trunk guards and staking on young trees
- Plan any new planting; order grafted trees early — good selections sell out quickly
- Review any shipping restrictions before ordering if you are uncertain of your state's status
Early Spring
Mar - Apr
- Apply copper bactericide at bud burst — the most critical timing for walnut blight prevention (OSU Extension)
- Apply a second copper application at full bloom if wet weather is persisting
- Monitor daily for late-frost forecasts; protect young trees with frost cloth if temperatures below 28°F are forecast during leaf-out
- Plant new trees once hard frost risk has passed
Pacific Northwest
In the PNW, bud burst timing is the most critical management moment of the year — the copper application window is narrow and wet weather during this period is normal. Mark the calendar and be ready to spray as soon as buds begin opening. Missing this window means walnut blight has a head start for the entire season.
Late Spring
May - Jun
- Apply modest balanced fertilizer in early May if shoot growth indicates a need — last effective timing
- Begin monitoring for husk fly and codling moth with pheromone or sticky traps
- Apply kaolin clay (Surround) to developing nuts if husk fly or codling moth pressure is anticipated
- Water young trees consistently; begin irrigation schedule for established trees if dry
Summer
Jul - Aug
- Maintain consistent irrigation — critical for nut sizing and kernel fill
- Monitor husk fly and codling moth traps; treat with spinosad per trap timing if threshold is reached
- Structural pruning should be done in this window (late summer preferred) — cuts heal cleanly with minimal sap flow
- Remove dead, diseased, or crossing wood; maintain central leader
Fall — Harvest
Sep - Oct
- Harvest when husks begin to split; collect fallen nuts promptly before moisture or wildlife damage occurs
- Hull nuts immediately; wear gloves to avoid permanent staining
- Wash and cure in a well-ventilated location for 2–4 weeks
- Dormant-season pruning can begin in late October–November once leaves have dropped and sap flow has slowed
Pacific Northwest
In western WA and OR, fall rains can begin in earnest before all nuts are down. Monitor trees closely from mid-September and collect nuts as they fall. Ensure curing is done indoors or under cover with good ventilation — the humid fall climate can cause mold on nuts left to cure in damp conditions.
Late Fall – Early Winter
Nov – Dec
- Structural pruning is acceptable in November–December after leaf drop and before Christmas, while sap flow is minimal but temperatures are above hard-freeze
- Remove and compost fallen husks and leaves from the root zone — reduces overwintering disease and pest inoculum
- Deep water if fall has been dry before the ground freezes
- Renew mulch around root zone; keep clear of trunk