Onion in Zone 6B — Pacific Northwest

Onions thrive in our Pacific Northwest climate, making them one of the most reliable crops for Zone 6B gardens. Our long, mild growing season gives onions plenty of time to develop those sweet, complex flavors that store-bought varieties can't match. The cool nights we enjoy during our dry summer months actually improve onion flavor by allowing the plants to focus energy on bulb development rather than dealing with heat stress.

While our cool, wet springs can slow down early growth and our shorter heat season means timing matters more than in warmer regions, onions are incredibly well-suited to our 162-day growing season. With proper planning, you'll harvest beautiful bulbs that store well through our wet winter months, giving you that homegrown taste year-round.

Starting onion seeds indoors isn't the most common approach here in the Pacific Northwest, but it's worth considering if you want the largest possible bulbs or specific varieties not available as sets. You'll want to start seeds from late January through mid-February, about 10 weeks before you plan to transplant outdoors.

Set up your seed trays in a warm spot (around 70°F) with good light once seedlings emerge. Bottom watering works well for onions since it prevents the thin seedlings from getting knocked over. The timing works nicely with our slow spring character - by the time your seedlings are ready to transplant in mid to late April, soil conditions are usually workable.

Keep in mind that onion sets (small bulbs) are much easier for beginners and give more reliable results in our climate. But if you're after specific long-day varieties perfect for our latitude, starting from seed indoors gives you the most options.

Transplant your indoor-started onion seedlings from mid-April through early May, once soil temperatures reach about 50°F consistently. The timing aligns well with our typical last frost period, though onions can handle light frosts without damage.

Harden off seedlings gradually over a week, starting with a few hours outdoors and increasing daily. Our overcast spring days actually make this process easier since there's less risk of shock from intense sun. Space transplants 4-6 inches apart in rows, giving them room to develop good-sized bulbs.

Watch for those unpredictable spring temperature swings we get in the Pacific Northwest. A sudden warm spell followed by cool, wet weather won't hurt established transplants, but newly set seedlings appreciate some protection during their first week in the ground.

Direct sowing onion seeds works well in our Pacific Northwest climate, though it requires a bit more patience than planting sets. You can sow from early April through mid-June, depending on whether you want large storage onions or smaller cooking onions.

For best results, wait until soil can be worked easily - typically mid-April in most Zone 6B areas. Our cool soil in spring means germination takes longer than in warmer regions, often 2-3 weeks. Sow seeds about half an inch deep and 4-6 inches apart, or plant closer and thin later for baby onions.

The easiest approach for most Pacific Northwest gardeners is planting onion sets (small bulbs) rather than seeds. Sets establish quickly in our cool spring conditions and give you a head start on the growing season. Plant sets pointed-end up, just barely covered with soil, in early spring when soil is workable.

Onions need consistent moisture throughout their growing season, which works well with our natural Pacific Northwest rainfall patterns. During our wet spring months, you'll rarely need to supplement watering. Focus on good drainage instead - onions hate soggy soil more than they mind being slightly dry.

As our dry summer months arrive, typically by late June, you'll need to provide about an inch of water per week. Use the finger test - stick your finger 2 inches into the soil near your onions. If it's dry at that depth, it's time to water. Water at soil level rather than overhead to keep the foliage dry and reduce disease risk.

The most critical watering period is during bulb formation in mid to late summer. Inconsistent watering during this time can cause splitting or poor storage quality. However, stop watering entirely once the tops begin to fall over and yellow - this signals that bulbs are ready to cure, and continued moisture will delay the process.

A light mulch of straw or compost helps retain moisture during our dry summer months while keeping weeds down. Our mild summer temperatures mean you don't need thick mulch like gardeners in hotter climates, and good air circulation around the bulbs is important for preventing rot.

Your onions will be ready for harvest from mid-July through mid-October, depending on when you planted and which varieties you chose. The key indicator is when about 75% of the green tops fall over naturally and begin to yellow. This typically happens after our 100-day growing season, right as we're enjoying those beautiful, extended fall days.

Don't wait for all tops to fall over - harvest when most have toppled and cure the bulbs in a warm, dry place for 2-3 weeks. Brush off soil but don't wash them, and leave the tops attached during curing. Our dry fall weather often provides perfect outdoor curing conditions on a covered porch or in an open garage.

For storage onions, timing the harvest before our first frost in early October is important. Even though onions are cold-hardy, you want those outer skins to dry properly for long-term storage. Green onions and cooking onions can be harvested earlier in the season as needed.

Once cured, properly stored onions should last through our wet winter months. Cut off the dried tops and store in mesh bags or braids in a cool, dry place with good air circulation.

Onion Thrips These tiny, slender insects create silvery streaks and spots on onion leaves, eventually causing the foliage to turn yellow and wither. You'll see small black specks (their waste) on damaged leaves. Our dry summer months can make thrips problems worse since they prefer hot, dry conditions.

Thrips are often more problematic during warm spells in late spring and summer. Encourage beneficial insects like ladybugs and lacewings by avoiding broad-spectrum pesticides. Reflective mulches can help deter thrips, and removing weeds around your onion bed eliminates alternate hosts.

Pink Root This soil-borne fungal disease causes onion roots to turn pink, then purple, and eventually black and brittle. Plants become stunted and may produce smaller bulbs. The disease thrives in warm, wet soil conditions that can occur during our transition from wet spring to summer.

Pink root persists in soil for years, so crop rotation is essential - don't plant onions in the same spot for at least three years. Improve drainage in heavy clay soils common in parts of the Pacific Northwest, and consider raised beds if your garden has persistent drainage issues.

Bolting Onions that bolt send up a central flower stalk, making the bulb bitter and reducing storage quality. You'll see a thick, hollow stem emerging from the center with a round flower head. This often happens when onions experience stress from temperature fluctuations or inconsistent watering.

Our variable spring weather can trigger bolting, especially if plants experience a warm spell followed by cool temperatures. Choose varieties suited to our day length (long-day onions work best in the Pacific Northwest), maintain consistent soil moisture, and avoid planting too early when temperature swings are more dramatic.

Pacific Northwest Specific Challenges: Our combination of cool, wet springs and dry summers creates unique challenges for onions. The slow soil warming can delay early growth, while our excellent conditions for slugs means protecting young plants is important. However, our mild summer heat and cool nights actually favor onion development once plants are established, and our long fall season gives plenty of time for proper curing.

Onions make excellent companions for many crops in Pacific Northwest gardens. Plant them near carrots - the onions help repel carrot flies while carrots' taproots break up soil for better onion bulb development. Lettuce and other cool-season greens appreciate the pest-deterrent effects of onions, and since these crops have different harvest times, they make efficient use of garden space during our long growing season.

Tomatoes benefit from onions' natural pest-repelling properties, and the timing works well since you can harvest early onions before tomatoes need the full space in mid-summer. Avoid planting onions near beans and peas, as onions can inhibit the nitrogen-fixing bacteria these legumes rely on. This is especially important in our region where cool soil temperatures already slow down beneficial soil microbial activity in spring.