onion

  • Grow at Home: Onions from seed

    Many people grow onions from sets - mini, immature onion bulbs - to get a head start.  The advantage of growing onions from seeds, instead of from sets, is that it is far cheaper if you are going for a big harvest. So if you eat a lot of onions then seeds are worth a try but you need to get them in ASAP now.

    Sowing

    Make sure you use fresh seeds as the germination rate reduces the older seeds get.  They will still germinate but if you are using a packet from last year you may need to sow a few more to get the crop you are hoping for.  Sow the seeds on a windowsill or in the greenhouse, from February to April.

    spring_onion_cutThey will germinate without extra heat, but providing a little heat underneath the seed trays or pots will speed up the germination process.  So, add a lid or enclose in a plastic bag and put it on a heat mat or somewhere warm like on top of the fridge.  Germination should take around 7 to 10 days.

    Onion seedlings sometimes have trouble shedding the seed husk and end up doubled up like an ostrich with their head in the sand.  If you want to help them move along then you can snip the thinner bit, pull it out complete with seed husk and discard it.  The thicker side of the loop can then get on with growing.  This is fiddly and they will sort themselves out eventually so you can decide if you have the time and energy to do this or want to just let them get on with it.

    Whether you are growing in the ground or containers make sure that that the young onions get plenty of light. If you are not growing in a greenhouse, then put the seedlings outside on warm sunny days to get maximum light benefit and to help harden them off. Use a large Bell cloche, poly lantern cloche or poly tunnel to help protect from wind and temperatures below 10˚c. Once you are happy that night time temperatures are well above 8˚C then the onions can stay out without protection.

    Planting Outside

    onions_growingTransplant them outside in May or June when they produce a third leaf and are about 3” (8cm) high. Dig some rich fertiliser into the ground where you are going to plant them.  Make sure you put it directly under where the onions will be as their roots are concentrated directly down from the bulb.

    Plant them vertically and handle them gently. The bulb should be ½” (1cm) below the surface. Depending on the onions final sizes, plant them between 2-10” (4-25cm) apart, with 9" (22cm) between rows.

    Container Growing

    If you want to grow onions in containers then transplant them at the same stage as for outdoors. The container will need to be at least 10" (25cm) deep and each onion will need about 8cm (3 inches) of space to grow. So, the wider the container the better.  Make sure that the compost you use to fill the container is not too high in nitrogen.  If it is you will get a lovely leafy display above ground and very little below ground.

    Looking after your Plants

    The important thing while they are growing is to keep the weeds down.  Onion seedlings don't compete well with weeds and it will affect the size of your onions.  So weed regularly.

    You can also keep trimming them back to around 5" so that they don't flop over.  Once again they will be OK if you leave them to their own devices, so if you're not growing them for the Village Show you may want to miss this step.

    Keep them well watered especially when it is dry. When the leaves start to turn yellow at the ends, bend the tops over to help with the ripening.  Possibly even clear a little of the soil at the top of the bulb too.

    Harvest

    onion_bulb_in_groundHarvest them from July to October.  Lift the onions as you need them from July to October.  There is a danger that they can rot in the ground when it starts to get very wet so harvest and store them before the end of October. After you lift them let them lie in the sun for a couple of days.

    Storage

    Only store the onions that are perfect - use any that aren't straight away.   The best way to store them is in a jute Veg Sack.  This allows air to circulate and keeps them cool and dark. They can keep in a well aired room for up to six months.

    Top Tip

    When peeling chopped onions, light a couple of candles.  This should stop your eyes watering, as the vapours from the onions will be absorbed in the candle flames.

  • Exploring the rhizosphere: how to grow trouble free onion sets...

    Rootrainers are what I've chosen for years to grow overwintering onion sets, garlic and spring planted onion sets. Onion sets (small immature onions) allow me to have onions all year round. But, originally manufactured to grow tree seedlings, why would I use Rootrainers for onion sets?

    Growing Onions using Haxnicks Rootrainers
    Growing onions from seeds can be a hit and miss affair, with weather, birds and the like all affecting the young seedlings’ growth outdoors, particularly those seedlings that have to overwinter. I am not after prize winning onions anyway or even huge onions so don't need to use onion seeds. I prefer sets. However, whenever I planted sets direct into the soil outdoors, within a few days, I would find many of the sets had been pulled up from where I had planted them and scattered all over the soil. Who or what was responsible?

    Some detective work - root zones and rhizospheres...

    The root zone is the name for the region of the soil around plant roots as they grow.  The roots produce secretions that help and protect them as they force their way downwards through the soil. The immediate area around the root is called the rhizosphere. There will be many rhizospheres within the root zone of a plant.

    The rhizosphere is the most dynamic environment in the soil, or a microbe ‘hot spot’, the fast food areas of the soil! The roots are also continually shedding old tissue and sloughed-off plant cells. The root secretions and dead plant cells are a feast for microbes living in the soil. In return the soil microbes provide nutrients for the plants, which encourage plant growth. More plant growth means more roots. A win-win situation! Hence soil microbes themselves congregate around the roots. Microbes in turn are a beacon for earthworms, who sense the root secretions and microbes in the soil and target such ‘hot spots’ to feast upon them!

    The Culprit!

    In my garden its the blackbird.  Blackbirds deliberately pull up the onion sets to seek out earthworms and other such tasty morsels, living and feeding in the root zone underneath the onion set.

    By planting onion sets in Rootrainers, the roots will grow in and around the compost, binding it together.  Then when planting them outdoors, unless the blackbird has fed on at least 3 Weetabix (!) that morning, it will not have the energy or strength to pull out the onion set with its well rooted fibrous compost ball, which is a lot heavier than an onion set on its own. Result:  no more scattered onion sets!

    Due to their size onion sets are great for children and school projects too.  Handling them is easy.  Planting requires less skill as sets are easier to handle than seeds.  Together, sets and rootrainers make the exercise easy and interesting for children to do for themselves. One major advantage for schools is that the children can grow AND harvest them all within the school year.

     

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