Garlic, bulbing onions, leeks, shallots and spring onions all belong to the allium family.

This family is particularly suited to Tasmania's cool climate as long as you obey a few simple rules about

when to plant them and when to feed them.

Basically alliums grow leaf and then set a bulb.

Their need for fertiliser stops once they start setting a bulb because they obtain the nutrition for the bulb

from the leaf they have grown.

This family is dependent on day length to determine when it will bulb and ultimately run to seed.

If you sow them at the wrong time you must expect failure.

Most alliums are biennial with a period of dormancy after bulbing.Many alliums bulb in response to increasing day length

after experiencing a winter and some others bulb in response to decreasing day lengths.

Ultimately the size of the bulb is determined by the size of the vegetative growth,

so the objective is to have them grow strongly in vegetative growth before setting a bulb.

I grow 4 types of alliums and rotate them through my garden beds,

never putting a member of the allium family in a bed that previously held alliums.

Carrots are an ideal crop to follow onions , and I usually make a late sowing of carrots on the patch I have harvested onions from or sow carrots in between the rows when I sow onions .

Alliums do not grow well on clay soils. They have a shallow compact root system that does not penetrate clay well at all.

Onions do best on well worked loose soils with a high degree of organic matter which is balanced with fertiliser they can use.

COF is most suitable for this family as they love lime.

If sowing seed it is best to prepare a bed with a compost layer about 2 cm thick on the surface

as this retains the moisture better than most soils.

Make the shallow seed drills by pushing the handle of your rake into the soil to make an impression.

This will compact the soil at this point and restore the capillary action between the sub soil and the compost.

If you sow your seed into this and keep it watered regularly the seed should germinate in 14-21 days.

Garlic Leeks Bulbing Onions


Garlic grows well in a cool climate. Garlic bulbs form a few centimetres below the soil surface.

If the soil becomes hard and compacted, the bulbs will be small.

Garlic grows best when allowed to grow strong leaf and overwinter before setting a bulb in the following Spring.

The best time to plant garlic for sufficient leaf growth is March.

In preparation of the bed, work the soil well to a depth of 30 cm and apply a dressing of COF or Dynamic Lifter at 250gms per square metre.

Plant the cloves with their top upwards at a depth of about 2.5 cm.

Water well and keep the bed moist until the shoots appear.

When the shoots appear, regular side dress the growing plants with COF until the cold of winter sets in.

The plants will put on another growth spurt in about September once the weather warms.

You can keep feeding them and watering them well until the end of October.

In November the tops will start to yellow. This is an indication that the plants are starting to bulb.

There is no further need for fertilise and no water.

About Mid December, you can pull the plants out of the ground, shake all the dirt off the roots

and leave the plants on the top of the bed to dry thoroughly.

During this time, the plants will store the available food in the leaves as they dry.

When the leaves are thoroughly dry you can braid the bulbs onto a string and hang in a cool dry place.

They should last almost over winter before starting to sprout if you have dried them properly.

I save the best of my garlic cloves for seed each year.


Leeks are fabulous to have in the garden when onions are not available.

I usually sow Leek seed in early September and then transplant the seedlings into a well worked fertilised bed

with about 400gms of COF per square metre about mid November.

This way you will have edible size leeks by December.

I prefer to harvest my leeks when they are about 2.5 cm thick.

They are tender and very tasty at this stage.

The leeks in the photograph were seedlings I purchased at a nursery in September

and transplanted at 12 cm spacings in seedling trenches about 3 cm deep.

Be careful not to bury the seedlings deeper than the first set of leaves or they will gather soil in the leaf nodules

and be difficult to clean when harvested.

You can hill up the soil slightly if you wish as the leeks grow, to ensure you have an adequate white section below the ground.


The same leeks in mid December. These are large enough to harvest if you wish.

They are tender and succulent when smaller like this.




Bulbing Onions

Bulbing onions are usually grown for their pungent flavour as a base for many dishes.

They are grown for keeping so it is desirable you catch the period of dormancy after they have set a bulb.

As all the onion family relies on strong leaf growth as a foundation for storing nutrients in the bulb,

the timing of sowing your seed is critical.

I usually sow seed in shallow drills in August.

The cool weather and the moisture available in the beds allows easier germination as this can be more difficult

as the soil dries out during the warmer months.

Fresh seed is essential. It is difficult to get fresh seed in Tasmania as there is a ban on the importing of onion seed.

Lots of seedlings are usually available in Tasmanian nurseries from August, so you may need to resort to these.

The Lost Seed has several varieties which are reliable if planted at the correct time.

Belvedere is a large, globe-shaped brown onion that is early maturing.

If the seed is sown in August, plants should mature in late summer and store well over Winter.

Cream Gold or Pukehoe is also an early variety and stores well.

Both of these onions are suitable for growing in a cool climate.

Remember, onions rely on strong vegetative growth to produce big strong bulbs.

The bulb will always depend on the size of the leaf grown.

It is important to keep feeding onions with side dressings of COF and water well to keep them growing strongly.

Once they start to swell at the base and the tops start to yellow, they have no further need for fertiliser and little need for water.

Stop watering and feeding, allowing the tops to brown and shrivel before pulling the onions and allowing them to dry thoroughly for storage.

Salad Onions

Salad onions such as the mild flavoured Odourless Onion are great for summer salads.

I usually buy seedlings after the month of July and transplant them into a bed that has been finely worked

and fertilised with 250 gms of COF per square metre.

By digging shallow trenches you can lay the onions bulb in the trench and backfill easily with your fingers.

Water the seedlings in well and regularly fertilise with Comfrey tea during the vegetative growth stage.

Onions rely on a strong vegetative growth stage and then store the nutrition of this in their bulbs

before throwing up a seed head in the next season.

When you notice the onions are starting to bulb, stop the water to the plants if you can

and allow the tops to die down and fall over.

You can them pull the onions and lay them on top of the bed until they have completely dried on top.

This way they should store well until the late winter.

Watch the video clip below to learn how to prepare onions for storage.


Preparing Onions for Storage


Spring Onions

Spring Onions are usually of the Sweet Spanish variety which can be grown in Spring and harvested before they begin setting a bulb.

This variety does not set a very strong bulb so they are best not grown through to try to achieve this.

Once again, regular feeding with COF or Dynamic Lifter will ensure strong growth during the Spring period.





Topsetting onions

Topsetting onions are perennial varieties that are suited to Tasmania's cool climate and are used like spring onions.

The tops set bulbets which overweight the top and allow the forming bulbs to seed in the grown about 3ocm away from the parent plant.

They are fairly aggressive in this habit, so need to be watched carefully if they are not to grow rampant and take over areas you don't want them. There are at least 2 varieties- Carawissa and Egyptian Walking.

Shallots/Potato Onions

Potato onions are an easy to grow variety and the tops are mild enough to use as Spring Onions.

I have personally never bothered with these, so if you are keen to grow them you will need to look elsewhere for good advice on how to grow them.

One thing I have learned from growing onions is that beans do not enjoy growing in the soil previously occupied by onions.

The beans will be stunted and not produce well.

I take it that the onions emit toxins in the soil which inhibit the growth of other competitive plants ( except weeds unfortunately).

These toxins remain after the onions are pulled.

Root crops such as carrots and beetroot do well in soil previously occupied by onions, so I usually follow an allium crop with these vegetables.







This page was last updated on 31/04/2013