Onions and Garlic
Garlic Quick Tips
When to Plant: Late summer to fall.
How to Plant: Plant individual cloves root-end
down, about 2" deep, 2" apart, in rows about 12"
Soil Type: Loose, sandy to silty with plenty of
Soil Temp: 40-100
Soil pH: 5.5 - 7.5
Fertilizer: High phosphorous such as 10-20-20
or bone meal at planting. High nitrogen in spring.
Onion Quick Tips
When to Plant: Plant seeds in the garden in
fall, or indoors in late winter. Plant sets or starts
several weeks before the last frost.
How to Plant: Plant seeds 1/4" deep and 1/2"
apart, in rows 6" to 18" apart. Plant sets or starts
1" to 2" deep, in rows 6" to 18" apart. Plant sets
or starts at least 4" apart for bulbs, closer for
Soil Type: Loose and well-drained.
Soil Temp: 40-100 degrees F
Soil pH: 6.0 - 7.0
Fertilizer: Use a high phosphorous fertilizer like
10-20-20, a complete organic fertilizer, or a
combination of bone meal and blood meal.
Onions and garlic, along with leeks, shallots, and chives, are members of the genus Allium. Alliums are
noted for their bulbs, and for the distinctive pungent flavor that is valued all over the world for the zesty
burst it adds to all sorts of dishes.
Onions tolerate a wide variety of climates and soil types. In general, a loose, light, well-drained,
moderately fertile soil is best to allow bulbs to grow unhindered. Onions have a very shallow root system,
so soil that holds moisture without becoming waterlogged is ideal. A generous amount of compost worked
into the soil will help meet all these needs.
There are two main types of onions, long-day and short-day, referring to how many hours of daylight they
need for bulb formation. In northern latitudes, where summer days exceed 14 hours, long-day onions will
do best. The varieties of onion sets we carry, and at most other local garden centers, are chosen with this
in mind. If you buy onions by internet or mail order, you'll want to pay attention to this detail.
Onions may be grown from seed, from transplants (starts,) or from small dormant onion bulbs called sets.
Planting from seed often produces a better quality crop, but it's a little more difficult than planting from
Seeds may be sown directly into the garden in fall, or started indoors 4-6 weeks before you plant them
outside as starts. If you plant directly into the garden, they will need to be thinned. Harvest some before
the bulbs start to expand for use as green onions or scallions, and continue thinning in this way until the
remaining plants are 4 inches or more apart. Band high-phosphorous fertilizer or a mixture of bonemeal
and blood meal along the row.
Sets and starts are planted in the garden in early spring. For full bulbs, plant at least 4 inches apart. If
you plan to use some for green onions, plant them closer, and thin until you reach the proper spacing. Dig
a furrow about 4 inches deep, and apply a band of high-phosphorous fertilizer or bone meal and blood
meal along the bottom. Cover it with 2 inches of soil, and plant the sets or starts on top, covering them
with another inch or two of soil. Make sure to plant sets with the pointed ends up. Smaller sets are more
likely to develop into full bulbs, while larger ones are prone to bolting (flowering.) Once an onion plant has
bolted, bulb development stops, so harvest these for green onions.
Onions need lots of phosphorous for bulb development. They also need nitrogen, but excess nitrogen will
result in plants that put too much energy into growth of foliage rather than bulbs. Good compost and some
bone meal, maybe with a little blood meal, are often all onions need to grow big delicious bulbs. Onions
need about an inch of water each week.
Weeding is very important for onions. Their shallow roots are vulnerable to competition from weeds, and
their sparse foliage doesn't shade the soil or crowd them out. When weeding or cultivating around
onions, take care not to disturb their roots.
By late summer, the tops of the plants will start to fall over. This is the sign that the bulbs are ready to
harvest. Dig them out, shake off excess soil, and leave them lying on top of the ground for a few days.
Then cut off the tops, leaving an inch or two of neck, and hang them in a dry place for a few weeks to
complete the drying. (Mesh bags work well for this.) Store them in a cool dry place, ideally just above
freezing, and under 40 degrees.
Garlic is best planted in late summer to fall, from late July to October, for harvest the next June or July.
Loose soil ranging in texture from sandy to silty is best for growing garlic. Add some compost before
planting, and work in some high-phosphorous fertilizer such as 10-20-20 or bone meal.
Plant individual cloves of garlic with the root side down, about 2" deep and 2" apart. You can apply a light
mulch now to help keep weeds down. From now until next spring, you won't see much happening, as the
plants are putting their energy into growing roots rather than leaves.
In the springtime, side dress with a high nitrogen fertilizer such as 16-16-16 or blood meal. Make another
application around early May. Keep weeds under control - garlic doesn't like competition!
In late June or July, withhold water from the plants for two or three weeks. When the tops have fallen over,
it's time to harvest the bulbs. Each clove will have produced an entire head of garlic. Dig up the bulbs,
brush off any soil clinging to them, and either hang them or lay them on a screen to allow air to circulate.
Allow them to cure for a few weeks in a dry place.