ONION & LEEK PLANTING GUIDE

Onions are the quintessential storage crop and the backbone of most recipes. A must have for any vegetable gardener, it pays to learn how to grow your own onions. Enjoy our Onion & Leek Planting Guide for information from planting to harvesting & curing.

Different Onion Offerings

Keene Garlic is happy to offer both Certified Organic Onion/Shallot/Leek Plants as well as Naturally Grown Onion Sets for spring planting.

Our Certified Organic Onion & Leek Plants are greenhouse-grown on small, family farms in Wisconsin. These live seedlings arrive in a container with soil, hardened off, and ready to plant. Our local organic onion growers prefer these onion starts because they are easy to grow with high yields.

Our naturally grown onion sets will arrive in a netted bag. Plant these small bulbs whole in spring for a summer bounty. They come in Red, White or Yellow, or order our NEW Onion Set Sampler. Upon arrival, unpack your onion sets from the box and store in a cool, dry place until it is time to plant.

Basic Onion & Leek Growing Info

• Sun Requirement & Timing: Onions require full sun – the more the better! Therefore, avoid planting next to crops that might shade your onions. It is typical to plant onions as early as 4 to 6 weeks before the last estimated spring frost.
• Soil Preparation: Alliums need full sun & loose, nutrient rich soil. Proper drainage is also key to growing great onions. Adding compost or a well-balanced organic fertilizer to the soil prior to planting is recommended, especially if your soil fertility is low. Our Keene Garlic Fertilizer is great for all alliums! If you have heavy soil, it is recommended to plant them in raised beds or raised bed rows at least 4″ high to promote sufficient drainage. 

Onion Planting Instructions

Plant onions close to the surface, making sure the roots are fully covered. It is best to plant into damp soil and water shortly after planting. There are a couple of good ways to plant onions:

Option #1:  Plant single onion plants 4” apart in rows that are 10-12” apart. Recommended.

Option #2:  Plant groups of 3 onion plants 10” apart in rows that are 10-12” apart. This allows for all 3 onions to spread out and grow to full size. This method allows for easier weeding between plants when they are small.

Watering & Weeding

Alliums have shallow root systems and do best with about 1 inch of water per week, especially during bulbing time. Alliums do not compete well with weeds so it is important to keep weed pressure down for optimum growth.

Fertilizing

It is recommended that you add a specialty fertilizer such as Keene Garlic’s Garlic Fertilizer (made for all alliums!) or an All-Purpose Fertilizer to the soil at the time of planting. You may reapply every 10-14 days until bulbing starts.

Pest & Disease Control

Adequate air flow & using crop rotation reduces the risk of foliar diseases in onions. Maintain proper spacing & keeping the weeds down will help reduce excess moisture.

Thrips are the most common pest of onions. Damage from these tiny pests appears as gray or silver markings on the leaves. They can be controlled organically with Neem oil, safer soap & Pyrethrin.

Harvesting & Curing

Onions can be harvested to eat fresh throughout the growing season. Harvest onions for storage once the tops start to turn brown and fall over. At this point, pull the onions and cure in the sun, if possible, for 2-4 days. You will then move them indoors to finish curing. If weather does not permit outdoor curing, spread onions in a single layer in a well-ventilated area. Fully indoor drying will likely add to the drying time. Onions need to be thoroughly dried for long storage.

Leek tops, however, do not die back when they are ready to harvest. Gently pull them in early fall and trim roots & tops.

Storage

Onions are fully cured and ready for storage when the necks are no longer green & are completely closed up. Trim dried leaves and store in a netted bag or crate with adequate airflow.

*Note: Sweeter onions have a shorter storage time so be sure to eat them first! Well-cured & properly handled onions can keep for up to 4-7 months.

Leeks should be stored in a plastic bag in the crisper drawer in the fridge.