Can you grow alliums from seed? A risky business, but worth a try

Pim Dickson, horticultural and technical content manager at Mr Fothergills, told us: “Time is the major factor, and providing the care needed to raise seedlings and young plants. This is easily countered by the savings made growing from seed [compared with buying bulbs], the large numbers you can raise and the pleasure taken in the process of growing your own.” 

While buying seeds is cheaper than bulbs, you can save money by propagating from the bulbs you already have, and we explain how later. 

It’s also worth being aware that your results from growing alliums from seed will be different than from bulbs. Simon Akeroyd, garden editor at Saga Exceptional says: “They may not be identical to the parent plant as it’s likely the seeds will have cross-pollinated. But if you’re keen to experiment then you could create a new variety by growing alliums from seed. However, you’ll have to wait a couple of years for the seeds to develop into full-size plants, whereas if you plant an allium bulb in the autumn, you’ll get a flower in the spring. But it’s fun to try – and that’s what gardening is all about.”   

Yes, without you having to put in any effort, alliums will self-seed. So, if you don’t remove the flower heads once they finish, you’ll find the seeds will be distributed naturally as the plant sways in the wind.  

However, this method doesn’t give you much say in where your seeds are planted. And you may also find you’re stuck without knowing what’s a seedling and what’s a weed. “It’s much better to sow them in rows or trays, where they can be easily weeded, properly nurtured and then planted out to final growing positions when plants are strongly developed,” says Dickson. 

It’s easy to see when allium seeds are ready to collect, Dickson says. You’ll notice that the flower heads have dried and the seeds are ripe. You’ll find the seed heads will change from green to brown and will start to split open to reveal the seeds.

There’s no science behind collecting allium seeds – all you need is a paper bag for storage. Just gently tap the seed head with your hand and hold the paper bag below to capture the seeds as they fall. If you regularly collect seeds, remember to label the bag, so you know what’s inside when you come back to use them later.  

You can go ahead and sow the ripe seeds as soon as you’ve collected them, or you can wait until the spring and pop them in the fridge to store – just make sure they are clearly labelled so you don’t mistakenly scatter them over your salad. 

“If sown outdoors or in trays kept outdoors in a cold frame, this will provide a natural process of cold stratification, where a period of cold breaks the seeds natural dormancy,” says Dickson. 

However, if you decide to sow the seed later in the year, and have stored it in the fridge, this will have provided the cold spell that is needed. 

Taking the ripe seed that you’ve just collected, scatter them over the soil where you want them to grow. Then, gently rake over the area. You’ll now need to be patient, as when growing alliums from seeds they can take a couple of years to flower.  

You can sow your stored seeds into trays at the beginning of the year. Remove them from the fridge and place in a gritty seed compost, no more than 0.5cm (0.25in) deep. Dickson then advises to “put them in an unheated frame or greenhouse and keep them moist.”

Once the seedlings have reached 10cm (4in) high, prick out the strongest ones and transplant them into individual pots. They can be left outside or placed in an unheated frame. Then, in the late autumn, transplant them into your garden, keeping the plants about 30cm (12in) apart, making sure you’ve added plenty of grit or drainage into the soil beforehand.  

But do remember, when growing allium’s from seed, you’ll have to be patient and wait a couple of years to see the results of your labour.

To give your alliums the best chance of developing into strong, healthy plants, it’s worth planting them in a soil type and position where they will thrive. For this reason, Dickson recommends “a fertile, quick–draining soil, in a sunny and sheltered position, as the flower stems are top heavy and easily knocked over by strong winds.”