[Lottie Digger]

Last year my onion sets never grew much bigger than sprouts - what did I do wrong?

[Yorkie]

Did you a) feed and b) water them during their growth?

[Lottie Digger]

I put growmore down before planting and watered.

[boddy]

I've had the same problem. This year I'm trying starting them off in trays to give them a boost - not sure if it will work but that's what I'm doing! Garlic however was very successful straight into the ground, still eating my first batch now.

[Salmo]

Last year my onion sets never grew much bigger than sprouts - what did I do wrong?

Onions are a long season crop. When did you plant them? They need planting now, or even a little earlier, much later and they do not have time to get big.

Spring planted sets grow roots and stem until the day length starts to get shorter, Summer solstice 21st June. That triggers them to bulb up. If they are still small at the trigger point they cannot make big bulbs. That is why the show growers sow onions on Boxing Day.

Autumn planted sets grow slowly through the Winter and as the day length gets longer they are triggered to bulb up. That is why it is important to plant early enough to develop large plants before Winter. This is even more important with some of the Japanese varieties

[ARPoet]

I always put sets into cells of MPC to get a good root start. As soon as the green shoots are about half an inch i dibber a hole and plant em out. I always pre dress the ground with Blood Fish and Bonemeal a couple of weeks before planting and again mid may. Still eating last summers onions.

[Lottie Digger]

Thanks for all your ideas. I planted in March in modules and on plot mid April so I guess it's the feeding I need to increase. I still have last years crop to eat to just very fiddly peeling.  ;0)

[Ivor Backache]

The only thing that has not been mentioned and could have a bearing, is spacing. The closer they are the smaller they become- think of spring onions. Minimum of 4" with rows of 1'. I make a bed with 6" gap each way.
It is not advisable to feed once they have bulked up- they develop a thick neck and don't store very well.

[Kleftiwallah]

Let's get the sillies over with first. Did you plant them the right way up!  Now something slightly more serious,  Did you dig a small hole into which you placed the sets?  If you just pressed them into the soil, this can/will compress the soil below and make early life difficult for the sets having to force their roots down through compacted soil.

Just a couple of thunks.   Cheers,  Tony.

[Lottie Digger]

Yes they were the right way up I planted in modules and planted out when shooting at 6 inch spacing using a dibber to make a hole big enough for the roots. Also might have been wet spring talking to others on my allotment. Leeks were skinny too!

[DD.]

I notice that you fed them before planting. It could be that the nutrients washed out of the soil.

I prefer to feed my little and often through the growing season.

[RJR_38]

Yes they were the right way up I planted in modules and planted out when shooting at 6 inch spacing using a dibber to make a hole big enough for the roots. Also might have been wet spring talking to others on my allotment. Leeks were skinny too!

Yes - my onions were RUBBISH last year and tiny compared to the previous year and I didn't change anything. Hertfordshire weather was not great and everyone on the plot had tiny onions thinking about it

[BabbyAnn]

I can't argue with any of the above comments - spacing, spring feed, growing period etc - but would like to add 2 more suggestions.  During the growing season, make sure the soil doesn't dry out.  The next magic ingredient is potash - as this article on The Role of Potassium in Onion Production explains:

Potassium is involved in the production and transport of carbohydrates and sugars to the bulb; enzyme activation; and synthesis of proteins. It also maintains the ionic balance and water status within the plant, thereby improving resistance to cold injury and drought.

So as well as the usual balanced feed during the growing season, start putting a top dressing of potash down from late spring (late May / early June) and again in early-mid July and that helps to bulk up the bulbs.  Also the sulphur in potash will give your onions their characteristic pungency (not necessarily stronger flavoured as that is down to genes)

[Nobbie]

Did you keep them well weeded? Onions don't cope with competition very well.

[devonbarmygardener]

I've always found the onions to be greedy feeders.

I start mine off in cut down toilet rolls untill they sprout, the put them in the ground and feed at that time, then I generally feed again a few weeks later with a feed specific to onion (it looks kind of like a multi coloured grit;))