How to Grow a Washington Navel Orange

Sun

Eight or more hours of direct sun daily produces the heaviest crop and the sweetest fruit. Six hours is the practical minimum and yields a lighter harvest with thinner-skinned fruit.

Indoors over winter, place the tree at the brightest south-facing window in the house, ideally with a grow light overhead to keep daily light totals up through short days.

Drainage

Sharp drainage is non-negotiable. The roots rot within days in soggy soil. Dig a one-foot test hole and fill it with water. If water sits past a few hours, build a raised mound 12 inches above grade or switch to a large container with a fast-draining citrus mix.

Soil

Sandy loam that drains fast and stays slightly acidic is ideal. Heavy clay holds too much water and starves the roots of oxygen. Amend clay yards with several inches of coarse compost worked into a wide planting area, or plant on a raised mound.

Space and frost protection

Give a standard tree 12 to 15 feet of clear space and a dwarf tree 6 to 8 feet. A south-facing wall or a spot next to a paved patio adds reflected warmth that protects from light frost.

Below 28 F, drape the canopy with frost cloth and run a string of incandescent holiday lights through the inner branches for gentle warmth. Hard freezes below 25 F damage the wood and can kill an unprotected tree.

Watering

Water deeply when the top 2 inches of soil dry out, soaking the basin until the wetting front reaches a foot down. In the ground, this usually works out to once a week through summer heat and every two to three weeks in cool months. Containers dry faster and may need water two or three times a week in hot weather.

Consistent moisture during fruit set and sizing prevents the fruit from splitting along the rind. Long dry spells followed by a heavy soak cause sudden swelling that cracks the skin. Mulch and a regular schedule are the fix.

Feeding

Feed monthly from late winter through early fall using a fertilizer labeled for citrus. These blends supply the extra nitrogen citrus needs along with iron, zinc, and manganese that prevent the yellow-veined leaves common in container-grown trees.

Stop feeding by early fall so new flushes harden off before cool weather. Skipping the late-summer cutoff produces tender growth that frosts back at the first cold night.

When to prune

Prune in late winter or early spring after the worst frost danger has passed but before the new growth flush begins. Avoid summer cuts that expose inner bark to direct sun and cause sunburn on the wood.

What to cut

Remove any dead, damaged, or crossing branches at the point of origin. Thin the canopy lightly to let sunlight reach the inner branches, which improves fruit set on the inside of the tree.

Cut suckers growing from below the graft union as soon as they appear. These shoots come from the sour rootstock and will overtake the variety if left in place. Rub them off with a thumbnail while they are small.

Thinning fruit

A young tree under three years old often sets more fruit than the branches can support. Thin clusters down to one fruit every 4 to 6 inches in early summer to prevent branch breakage and to size up the remaining fruit. Mature trees regulate themselves and rarely need hand-thinning.

When it's ready

Fruit color is not a reliable ripeness signal for navels. Many fruits color up weeks before the flesh sweetens. The honest test is taste. Pick one fruit from the south-facing side of the tree and try it. If the flesh is sweet and juicy, the rest are ready. If still tart, wait two weeks and try again.

Once ripe, the fruit stores on the tree for a month or more without losing quality. This is the closest thing in the garden to a refrigerator on the tree.

Picking and storing

Cut the stem flush with the fruit using hand pruners. Pulling the fruit off tears the rind and shortens storage life. Wear long sleeves while picking, since the leaves and stems can be lightly thorny.

Stored at cool room temperature, picked navels keep for one to two weeks. The refrigerator extends that to three or four weeks. Wash only right before eating to keep the rind intact and slow mold.

Fruit drop in early summer

Most trees drop a portion of their small green fruit in May or June. This is normal self-thinning and not a sign of stress. The tree keeps what it can ripen and lets the rest go.

Yellow leaves with green veins

Iron or zinc deficiency, which is common on alkaline soils and in containers. Apply a chelated micronutrient spray to the foliage for fast correction and switch to a fertilizer labeled for citrus that includes these minor elements. Re-test soil drainage, since waterlogged roots also produce this look.

Fruit splitting along the rind

Uneven watering during fruit sizing causes a sudden swelling that cracks the skin. Mulch the basin to even out soil moisture and water on a regular schedule rather than waiting until the tree wilts. Split fruit cannot be salvaged but the rest of the crop is fine.

Leaf drop after a cold night

Cool damage causes leaves to drop within a few days of an exposure below 30 F. The tree usually recovers as new growth pushes in spring. Do not prune the bare branches until you see where buds break, since damaged-looking wood often surprises you with new growth.

Aphids curling new shoots

Small green or black insects clustered on new flushes cause the tender leaves to cup and curl. Knock them off with a strong water spray. Heavy infestations respond to insecticidal soap. Healthy ladybug populations usually keep aphid numbers in check on outdoor trees.

Sticky leaves and black sooty mold

Scale insects or whitefly are excreting sugary honeydew, which a black fungus grows on. Wipe individual scales off with a cotton swab dipped in rubbing alcohol. Spray horticultural oil in late winter to smother overwintering scale eggs. The sooty mold washes off with soapy water once the insects are controlled.

Tiny green caterpillars chewing new leaves

Orangedog or citrus leafminer larvae feed on tender new growth. Orangedogs are large and easy to hand-pick. Leafminer trails inside the leaf are cosmetic on a mature tree and the tree shrugs them off. A young tree with heavy leafminer damage benefits from a spinosad spray on the spring flush.

Branch dieback after a wet winter

Root rot from saturated soil. The fungal damage shows up at the top first because the roots can no longer feed the canopy. Check drainage and pull mulch back from the trunk. Cut dieback back to live wood and avoid overwatering until the tree rebuilds.

Sunburn on exposed bark

After heavy pruning or a sudden defoliation, the inner bark scalds in direct sun and cracks open. Paint exposed trunks and major limbs with white latex paint diluted 1 to 1 with water to reflect heat. Going forward, prune lightly and leave a leafy canopy to shade the wood.

Sucker growth from the rootstock

Vigorous shoots from below the graft union have larger, thornier leaves than the variety and will produce sour fruit if allowed to grow. Rub them off as soon as they appear or cut them flush with the trunk if they have hardened off. Letting one go for a year can take over the tree.

Wind-rocked trunk on a young tree

A newly planted tree in a windy spot rocks at the base, opening a gap that fills with water and rots the crown. Stake the tree loosely with a soft tie for the first year, then remove the stake so the trunk thickens. Mulch firmly around the base.