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Backyard Gardener: Growing bulb onions | News, Sports, Jobs


(Photo Illustration/MetroCreative)

Hello Mid-Ohio Valley Gardeners! We say goodbye to July this week as we see the hottest temperatures of the summer. Make sure you stay well hydrated out there, and do not work too long in the hot midday sun.

This week I want to talk about onions (Allium cepa). As the famous cook Julia Childs said, “It’s hard to imagine a civilization without onions.” We often consider onions an easy crop to raise in the garden. They can be grown anywhere in the garden where the soil is well-drained and there is full sun exposure.

However, many backyard gardeners are often disappointed when their onions fail to form large bulbs by the end of the season. If your onions do not measure up this summer, here are some recommendations for next year.

Make sure you choose the right variety. Onion varieties can be divided into three distinct categories: long-day, short-day and intermediate-day type onions. Onion plants rely on daylength to determine when they will start to form bulbs.

Long-day onions start forming bulbs when they receive at least 14 hours of sunlight each day. These varieties are best for West Virginia gardens, where summer days are long, and onions will have plenty of time to grow multiple leaves before bulb formation starts.

Short-day onions are a better choice for the deep south, because they only need 10-12 hours of light to initiate bulb formation. In our area they will most likely only produce small bulbs. Intermediate-day varieties start growing bulbs when daylength reaches 12-14 hours. These are also unlikely to form full size bulbs in northern gardens.

Make sure you’re growing bulbing, not bunching onions. Bunching onions will grow into scallions, and they will never form large bulbs. Shallots will also stay much smaller than yellow, red or sweet onions.

It is crucial to plant bulbing onions on time. Onions can be grown from seeds, sets, or transplants. Seeds require the most work, but are less expensive. Sets or transplants are more easily grown for optimal yield. Onions can be planted early spring or as soon as the soil is workable.

Planting onions too late usually results in disappointingly small bulbs. If you intend to grow onions from seed, you might want to start them indoors in the late winter/early spring to give them a jump start. Start onion seeds 10-15 weeks before you anticipate being able to transplant them into the garden, between mid-February and mid-March.

Onions will tolerate light frost and can be planted in the garden in late April or May. It is also possible to directly sow seeds in the garden as soon as soil can be worked in the spring, but the resulting onions will likely be smaller.

Onion sets can also be planted as soon as the soil can be worked. Sets are small, juvenile bulbs that have been stored over the winter. Sets provide for an earlier harvest but won’t necessarily result in larger onions, just onions that mature faster.

They are a dependable way to ensure a harvest. The only risk is that they might bolt (flower prematurely) if they are exposed to cold temperatures in the spring. Larger sets usually aren’t better than smaller ones because they are more likely to form flowers. Onions that flower develop mushy bulbs that are no longer edible you see a flower head forming, harvest and eat that onion as soon as possible.

Another key for growing bulb onions is to thin the plants. When onions have to compete for sunlight, water and nutrients, they will often fail to produce many leaves as they need to grow large bulbs. Each onion leaf equates to a ring on a bulb, so a greater number of large, healthy leaves means bigger onions.

If onions are planted too close to one another they will compete with one another, resulting in smaller bulbs. Whether direct seeding, transplanting seedlings or planting onion sets, onions should be spaced 3-4 inches apart to maximize growth.

You need to be diligent about controlling weeds with onions. Onions tend to have very shallow root systems, which makes them poor competitors against neighboring weeds. One strategy to keep the soil around onions weed-free by mulching with a thick layer of grass clippings, shredded leaves or clean straw.

Frequent shallow cultivation between onion rows can also be effective. Simple hand tools are often all that is needed, just be careful to avoid disturbing onion plants. Shallow root systems mean they will come dislodged from the soil with little provocation, especially when they are young.

Onions need frequent watering. Shallow roots also mean onions will dry out faster than other crops. They need frequent irrigation throughout the growing season in order to grow optimally. The rate of photosynthesis and growth slows down as soon as plants are moisture stressed, thus the upper few inches of soil should be kept moist but not soggy.

It may be necessary to water once or twice a week depending on the weather. Stop watering once the tops begin to yellow and fall over to encourage the bulbs to finish maturing and to avoid rot issues.

Onions tend to grow very well in rich, organic soils with a pH at 6.5-6.8.Lean, acid soils can limit growth. Get your soil tested to make sure the pH is appropriate and key nutrients are available. Onions do benefit from proper fertilization (ideally based on soil test results), though high nitrogen fertilizers should be used with caution. Excessive nitrogen can delay bulb formation, maturity and the storability of onions.

Question of the Week: Why are my garden beans flowering but not producing beans?

There are normally three reasons garden beans will flower but not produce fruit. High temperatures is the most common cause. Beans prefer temperatures between 70 and 80 degrees F. If the temperature remains above 85 degrees F, the flowers often drop (referred to as blossom drop) or they dry up on the plant (called bud blast). Hot, dry winds can make this condition worse.

Extreme fluctuations in soil moisture can also be a cause. Too much soil moisture can be as harmful as too little, as excess water limits oxygen reaching the roots. Extended rainy periods or extended drought can cause bean plants to produce few pods. You can irrigate during dry periods to alleviate drought but it is difficult to deal with excess moisture other than to use raised beds or berms to grow beans.

Letting pods mature on the plants: Maturing pods cause the plant to put energy into making seed rather than forming new beans. Keep plants picked even if pods are too mature to use.

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