Gladstone onions are recognized for their mild flavor and substantial size. This intermediate-day onion is a popular choice for many gardeners. Its adaptability makes it suitable for cultivation across a wide range of growing regions.
Unique Characteristics and Culinary Applications
Gladstone onions develop into medium to large globe-shaped bulbs, 4 to 5 inches in diameter. These onions feature clean white skins and firm flesh, contributing to their crisp texture. Their flavor is notably mild and sweet. This mildness is often attributed to a lower sulfur content.
The sweet flavor of Gladstone onions makes them versatile in the kitchen. They are well-suited for raw applications like salads, salsas, sandwiches, and burgers without overpowering other ingredients. These onions also maintain their qualities when cooked, making them ideal for grilling, roasting, or pickling. Gladstone onions possess moderate storage potential.
Cultivating Gladstone Onions
Gladstone onions need full sun exposure. The soil should be well-drained and rich in organic matter, ideally a loose sandy loam. An optimal soil pH range of 6.2 to 6.8 is important, as onions are sensitive to acidic conditions.
Gladstone onions can be started from seeds or transplants. Start transplants indoors 10 to 12 weeks before the last expected frost. Direct seeding outdoors is possible as soon as the soil can be worked, 4 to 6 weeks before the last frost, when soil temperatures reach at least 45°F. When planting seeds, a depth of 1/4 inch, with a spacing of two seeds every 4 inches, later thinning to one plant every 4 inches once seedlings reach 2 inches tall. For larger bulbs, space plants 4 to 6 inches, with rows 18 to 30 inches apart.
Consistent moisture is important, requiring approximately 1 inch of water per week, especially during hot and dry periods. Due to their shallow root system, frequent, light irrigation is needed. Incorporate compost or a balanced organic fertilizer at planting time. Apply nitrogen around 80 pounds per acre, with a side dressing 4 to 5 weeks after planting. Discontinue high nitrogen fertilizer once bulbing begins.
Regular cultivation is important to prevent reduced bulb size. Gladstone onions are intermediate-day varieties, requiring 12 to 14 hours of sunlight for proper bulb formation. They grow best in the middle latitudes of the U.S., between 32 and 42 degrees.
Harvesting and Storing Your Crop
The primary indicator of maturity is when onion tops begin to yellow or brown and naturally fall over. Harvest in the morning, gently lifting the bulbs from the soil using a garden fork to minimize damage.
After harvesting, cure onions by drying the bulbs in a warm, dry, well-ventilated area for several weeks. Initially, leave them in the garden for 2 to 3 days with light straw covering to prevent sunscald. Move them to a sheltered location where temperatures are between 75 and 80°F. Spread onions in a single layer with good air circulation during this 2 to 3-week curing period.
Onions are fully cured when their skins become papery, leaves shriveled, and roots feel dry and wiry. Following curing, trim roots to about 1/4 inch and green tops to 1 inch to prevent decay. For long-term storage, keep cured Gladstone onions in a cool (35-40°F), dark, dry place with good air circulation, such as in mesh bags or flat boxes with holes.
Troubleshooting and Growing Tips
Bolting
Bolting, the premature development of a flower stalk, is often triggered by environmental stress, including sudden temperature fluctuations. To minimize bolting, select intermediate-day onion varieties suited to the region and plant at the correct time. Protect young plants from early season cold snaps with horticultural fleece and ensure consistent watering during hot, dry periods. If an onion bolts, harvest and use promptly, as bolted onions do not store well.
Pests and Diseases
Pests like onion maggots, with larvae feeding on roots and causing wilting or stunting, can be managed with crop rotation, beneficial nematodes, or row covers. Thrips thrive in hot, dry conditions, leading to yellowing foliage and stunted growth; overhead irrigation can discourage them. Downy mildew, which prefers cool, humid conditions, can be addressed by planting in well-drained areas, avoiding overhead irrigation, and ensuring good air circulation by orienting rows with prevailing winds. Gladstone onions possess resistance to pink root.
Other Growing Tips
Crop rotation maintains soil health and prevents pest and disease buildup. Rotate onion crops every three to four years to disrupt pest cycles and reduce soil-borne diseases like white rot. Onions can follow crops such as corn, wheat, potatoes, or brassicas. Companion planting offers benefits. Carrots, brassicas (like cabbage and broccoli), lettuce, spinach, beets, and peppers are good companions for onions, deterring pests or enhancing growth. Herbs such as mint, parsley, savory, and thyme can deter onion flies.