Harvesting and storing onions

Since I wrote the post about starting to harvest our onions, shallots and garlic, I’ve had a number of emails from people asking about onion harvesting and storage.

The first thing I have to tell them is that in many ways it’s too late to start thinking about harvesting and storage now as many of the decisions have to be made before the crops go in.

So, I’ll wind the clock back to the start of the process and work my way through that before detailing the final means of storage.

The first decision to make is to calculate how many onions you want to store and for how long.

In our case, we need at least 10 month’s worth of onions. We use about 10 onions a week, which means aiming to have 450 edible onions in storage.

We then have to allow for spoilage - a noticeable proportion will have to be removed early on as examples with unseen rot or damage come to light, then a small proportion are removed over the following six to eight months, and finally about one in three or four go off in the final couple of months.

All up, it means allowing an extra 25 percent for spoilage, to give about 560 onions.

But to harvest 560 onions, you also have to allow for seeds that fail to germinate, sets that fail to grow, pests, disease, wind damage, lack of rain (or too much), lack of sun (or too much) and even theft.

In our location and conditions, that means allowing an extra 50% for wastage. That means planting at least 850 onions, which is a considerable amount of space and a vast amount of work. Both of which we’re able to supply.

The same calculation applies for garlic and shallots but with different variables.

In the case of garlic, there’s no point in trying to meet our year-round need as the Scottish climate is not conducive to reliable and regular crops.

So it’s a gourmet vegetable, with about 10 heads broken up and planted in a single bed as part of the rotation, and regarded as a useful treat if it grows well.

Shallots, on the other hand, have proved extremely reliable and free of disease for the third year in a row. They also last extremely well with the last ones being used 11 months after harvest.

Having decided to grow 850 onions, the next consideration is the varieties.

The best-keeping onions are late maturing onions with thin necks, grown from seed, but again, we have to factor in the Scottish weather.

Onions grown from seed have to be sown thickly into trays in February, have their tops clipped to about three inches in late March and then be set out in rows in April.

This gives the onions plenty of time to grow, develop and mature through the long days of summer.

That’s all very well in the southern parts of the UK, or anywhere else with a suitable climate,  but we have bitterly cold weather through until May, limited space to start crops under glass and soil temperatures can remain cold right through summer (as they have this year).

We do grow some onions from seed, especially hard-to-find varieties, but by and large we grow the bulk of our onions from sets, which can be poked into the ground as soon as the soil is workable (usually in late March).

Sets have a good head start, even if the weather is against them, and while we do lose a few to rot most thrive and are ready for harvesting in late August or early September, several weeks before the seed-grown onions.

This is another advantage as it means that even if unfavourable weather checks the final maturing of the seed-grown onions, we still have the crop grown from sets in storage already.

Thus far, the plan for harvesting and storing onions is to plant at least 850 with the majority grown from sets and an emphasis on thin-necked varieties that store well.

This year, our choices were 300 Sturon sets, 300 Stuttgarter sets and 150 Turbo sets.

Sturon  is a large, brown onion that stores well, has nice crisp flesh and good flavour once the bulbs have matured in storage. They can be very hot and sharp when first lifted.

Stuttgarter is a flattened brown onion with a lot of flavour, but it hasn’t grown as well for us as Sturon.  It does store well, though.

This is the first year we’ve tried Turbo, but they are said to store well and be less prone to bolting. We planted these at the same time as the others, but they’re further behind in terms of maturity compared with Stuttgarter and Sturon.

For seed-grown onions, we went for Rossa de Milano (for immediate eating), Long Red Florence (for immediate eating in salads), Batun (a bunching onion), Balaton (an experiment to see if we could grow them to maturity) and Dorato di Parma (some leftover seeds).

We planted out 300 onion seedlings in all, potentially giving us 900 onions.

The key things to remember with onions are that too little water will result in a much stronger flavour, they must be kept free of weeds and they need the benefit of those long summer days so they must be planted out as soon as possible.

Having successfully grown the onions, we now come to the part that I’ve been asked about - harvesting.

The usual advice is to wait until a third to a half of the onion stalks have fallen over naturally, and then carefully knock down the remaining tops with the back of a rake.

You’re then supposed to wait another week or so while the onions dry in the ground before lifting them and allowing them to dry in the sun for three days to a week.

But that pre-supposes warm, dry weather and not the Scottish damp.

In our case, once about a quarter of any given variety of onion has fallen over, we regard them as ripe for lifting and keep watch for a break in the weather.

As soon as we get a clear, sunny spell with little or no clouds in sight, we lift the onions and lay them out on the tarmac in the steading.

The combination of heat from the tarmac, plus the direct sun gets the drying process off to a good start.

The onions only stay outside for as long as the weather is dry and at the slightest hint of rain, they’re bundled inside to dry on racks in the byre.

We keep the upper halves of the stable-type doors open during the day to ensure good airflow and let the onions cure for at least a three weeks - longer if there’s any green or moisture in the necks.

Should the sun appear during the first week, the onions are brought back outside and then taken back in again at nightfall or when the damp returns.

The  stalks are cut off to one-inch stubs after the first week.

Once the onions have cured, we put them in net bags and hang them up from the rafters in the hayshed. The good airflow keeps them cool and dry over the coming months.

Onions intended for immediate eating have their stalks cut slightly longer and are braided into strings. Some are left to hang in the hayshed, while the rest are hung on hooks in the kitchen ceiling - this is not a long-term storage method as they start to grow after a couple of months.

If the onions start to sprout, they’re not wasted as the green tops make a delicious addition to soups, salads and stir-fries in later winter and early spring.

Garlic and shallots are harvest and stored in a similar way, but with the garlic all braided into strings while the shallots are stored in net bags.

And when we’ve lifted the very last onions of the season in early autumn, it’s time to start planting garlic for the following year and to plan the next season’s harvest of onions and shallots.