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Purple Top Walla Walla

Allium cepa 'Purple Top Walla Walla'

The sweet, mild onion that made Walla Walla, Washington famous. This beloved heirloom variety produces large, flattened bulbs with purple-tinged skin and crisp white flesh so sweet they can be eaten like apples. Perfect for those who want to grow their own version of this premium market onion.

Harvest

125-300d

Days to harvest

📅

Sun

Full sun

☀️

Zones

5–10

USDA hardiness

🗺️

Height

12-18 inches

📏

Planting Timeline

Zone:

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Direct Sow

Harvest

Direct Sow

Harvest

Showing dates for Purple Top Walla Walla in USDA Zone 7

All Zone 7 allium →

Zone Map

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Purple Top Walla Walla · Zones 5–10

What grows well in Zone 7? →

Growing Details

Difficulty

Moderate

Spacing4-6 inches

SoilWell-drained, fertile loam with high organic matter

pH6.0-7.0

Water1 inch per week, consistent moisture early season, reduce near harvest

SeasonCool season

FlavorExceptionally sweet and mild with low sulfur content, crisp texture

ColorPurple-bronze skin with white flesh

Size3-5 inches diameter, 8-16 oz

Zone-by-Zone Planting Calendar

Zone	Indoor Start	Transplant	Direct Sow	Harvest
Zone 1	—	—	June – July	December – September
Zone 2	—	—	May – July	December – September
Zone 11	—	—	January – February	July – December
Zone 12	—	—	January – February	July – December
Zone 13	—	—	January – February	July – December
Zone 3	—	—	May – June	December – October
Zone 4	—	—	April – June	November – October
Zone 5	—	—	April – May	November – November
Zone 6	—	—	April – May	November – November
Zone 7	—	—	March – May	October – November
Zone 8	—	—	March – April	October – December
Zone 9	—	—	February – March	September – December
Zone 10	—	—	January – March	August – December

Succession Planting

Direct sow Purple Top Walla Walla every 3–4 weeks from March through early May in zone 7, stopping once daytime highs are consistently above 75°F — onions started too late won't size up properly before summer heat shuts down bulb development. A fall sowing is worth trying: seed in late August, aiming for pencil-diameter seedlings before first frost, and you'll pull full-sized bulbs the following June or July. Don't approach this the way you would lettuce or radishes — stagger plantings to spread out your curing and storage work, not to hit a continuous harvest window. One well-timed large planting, cured right, keeps through winter.

Complete Growing Guide

Light: Full sun (6 or more hours of direct sunlight a day). Soil: High Organic Matter, Loam (Silt), Sand. Soil pH: Alkaline (>8.0), Neutral (6.0-8.0). Drainage: Good Drainage, Moist. Height: 1 ft. 0 in. - 1 ft. 6 in.. Spread: 0 ft. 6 in. - 1 ft. 0 in.. Spacing: Less than 12 inches, 12 inches-3 feet. Maintenance: Medium. Regions: Coastal, Mountains, Piedmont.

Harvesting

Flowers wither and convert to bulblets

Type: Capsule.

Harvest time: Summer

Edibility: The bulb and tops are edible raw or cooked. However, the plant also has poisonous characteristics as noted in the "Poisonous to Humans" section of this record. Toxicity can depend on the age of the person or animal, the age of the plant, the part of the plant ingested, how much is ingested, whether the person or animal has sensitivities or allergies, whether it's eaten raw or cooked, and so forth. Consult with a medical professional for further details.

Storage & Preservation

Fresh Purple Top Walla Walla onions require immediate curing after harvest. Spread them in a single layer in a warm, dry, well-ventilated area for 2-3 weeks until necks are completely dry and papery. Unlike storage onions, Walla Wallas have high water content and low sulfur, giving them only 1-3 months storage life even under ideal conditions.

Store cured bulbs in mesh bags or ventilated boxes at 32-35°F with low humidity, checking regularly and using any with soft spots immediately. For longer preservation, slice and freeze them for up to 8 months, or caramelize and freeze in portions. They also pickle beautifully – their mild, sweet flavor makes excellent quick pickles or pickled onion rings. Dehydrating works well too, though you'll lose some of the characteristic sweetness that makes this variety special.

History & Origin

Origin: Central Asia and central Persia

Considerations

-Toxic: Low severity

Companion Plants

Carrots run 6–10 inches deeper than onion bulbs, so they're not competing for the same soil zone, and the mingled scents of the two crops genuinely confuse carrot fly (Psila rosae) and onion thrips — not a guarantee, but worth the zero extra effort. Marigolds (Tagetes spp.) earn a spot at the bed edge by suppressing soil nematodes through alpha-terthienyl released from their roots. Beans and peas are the ones to pull off the list: they fix nitrogen at levels that shunt onion energy into tops rather than bulb sizing, and their root exudates appear to slow Allium development even before the nitrogen imbalance kicks in. Sage competes aggressively for the same surface moisture and doesn't offer anything in return.

Plant Together

Carrots

Onions repel carrot fly while carrots help break up soil for onion bulbs

Tomatoes

Onions deter aphids, spider mites, and hornworms from tomato plants

Brassicas (Cabbage, Broccoli)

Onions repel cabbage worms, aphids, and flea beetles

Lettuce

Onions provide natural pest deterrent while lettuce doesn't compete for space

Peppers

Onions help repel aphids and other soft-bodied insects that damage peppers

Strawberries

Onions deter slugs, aphids, and other pests that commonly attack strawberry plants

Roses

Onions help repel aphids, thrips, and may reduce black spot disease

Marigolds

Both plants repel nematodes and various garden pests when grown together

Keep Apart

Beans

Onions can inhibit nitrogen fixation in legumes and stunt their growth

Peas

Allelopathic compounds from onions interfere with pea plant development

Asparagus

Onions can inhibit asparagus growth and reduce spear production

Sage

Both plants compete for similar nutrients and can inhibit each other's growth

Nutrition Facts

Calories

40kcal(2%)

Protein

1.1g(2%)

Fiber

1.7g(6%)

Carbs

9.34g(3%)

Fat

0.1g(0%)

Vitamin C

7.4mg(8%)

Vitamin A

0mcg(0%)

Vitamin K

0.4mcg(0%)

Iron

0.21mg(1%)

Calcium

23mg(2%)

Potassium

146mg(3%)

Per 100g serving. % Daily Value based on 2,000 calorie diet. Source: USDA FoodData Central (FDC #170000)

Pests & Disease Resistance

Resistance

Moderate resistance to pink root, susceptible to downy mildew and thrips damage

Common Pests

Onion thrips, onion maggot, cutworms

Diseases

Downy mildew, purple blotch, neck rot, pink root

Troubleshooting Purple Top Walla Walla

What you'll see, why it happens, and what to do about it.

Silvery streaking or stippling on leaves, tips browning and curling, visible around midsummer

Likely Causes

Onion thrips (Thrips tabaci) — they rasp the leaf surface and suck sap; populations explode in hot, dry weather
Crowded planting that limits airflow and makes it easier for thrips to hide in leaf axils

What to Do

1.Spray with insecticidal soap or spinosad early morning when thrips are active, hitting the base of leaves where they congregate
2.Keep spacing at least 4–6 inches — don't cheat it — so air moves through the bed
3.Remove and trash heavily infested outer leaves; don't compost them

Pale gray-purple fuzzy growth on leaf surfaces, leaves collapsing inward, usually in cool wet spells

Likely Causes

Downy mildew (Peronospora destructor) — spreads fast in temps between 45–60°F with humidity above 85%
Overhead irrigation or prolonged leaf wetness from rain

What to Do

1.Switch to drip irrigation if you're overhead watering; wet foliage is the primary driver here
2.Apply a copper-based fungicide at first sign of symptoms, following label rates — copper won't cure infected tissue but slows spread to healthy leaves
3.Pull and destroy badly infected plants; the disease overwinters in debris and bulbs

Bulbs rotting from the neck down at harvest or in storage, with a soft gray-brown collapse

Likely Causes

Neck rot (Botrytis allii) — enters through the neck tissue if tops aren't cured properly after pulling
Harvesting too early before tops have started to fall naturally, leaving necks moist and open

What to Do

1.Wait until at least 50–75% of tops have fallen over on their own before pulling; don't force them down
2.Cure bulbs in a warm, dry spot with good airflow for 2–4 weeks before moving to storage — a screen or slatted rack works better than a solid surface
3.Cull any bulb with a soft neck immediately; one rotting bulb in a crate will take neighbors with it

Frequently Asked Questions

How long does Purple Top Walla Walla onion take to grow?▼

Purple Top Walla Walla onions take 125-300 days to mature depending on your growing method and climate. Starting from seed indoors in late winter for spring transplanting typically results in harvest in late August to September. In mild climates (zones 7-9), fall-sown seeds that overwinter will produce larger bulbs the following summer, taking the full 300 days but yielding premium-sized onions.

Can you grow Purple Top Walla Walla onions in containers?▼

Yes, but choose large containers at least 12 inches deep and wide to accommodate the substantial bulb development. Use well-draining potting mix enriched with compost, and ensure consistent moisture throughout the long growing season. Container-grown bulbs may be smaller than field-grown ones, but the sweet flavor remains excellent. Place containers in full sun and fertilize regularly since nutrients leach faster in pots.

What does Purple Top Walla Walla onion taste like?▼

Purple Top Walla Walla onions are remarkably sweet and mild with very low sulfur content, making them sweet enough to eat raw like an apple. They have a crisp, juicy texture when fresh with virtually no harsh bite or burning sensation. The sweetness intensifies when cooked, caramelizing quickly due to high natural sugar content. This makes them ideal for fresh eating, salads, and quick-cooking applications.

When should I plant Purple Top Walla Walla onion seeds?▼

Start seeds indoors 10-12 weeks before your last spring frost date, typically January through March depending on your location. Transplant outside 4-6 weeks before the last frost. In mild winter areas (zones 7-9), you can direct sow seeds in fall for larger bulbs the following year. The key is giving them a long, cool growing period followed by warm summer weather for bulb development.

Are Purple Top Walla Walla onions good for beginners?▼

These onions are moderately challenging due to their long growing season and specific requirements. Beginners can succeed with proper planning, but they're more demanding than standard storage onions. The main challenges are timing the long season correctly, managing moisture consistently, and dealing with their susceptibility to certain diseases. Start with easier onion varieties first if you're new to growing onions from seed.

How do Purple Top Walla Walla onions compare to regular sweet onions?▼

Purple Top Walla Wallas are significantly sweeter than most commercial sweet onions, with lower sulfur content and higher sugar levels. Unlike Vidalia or other sweet onions that are bred varieties, these are true heirlooms with more complex flavor. However, they store much shorter (1-3 months) compared to other sweet onions that may last 4-6 months. The tradeoff is exceptional fresh eating quality versus storage life.