Green Onions & Leeks

By September 28, 2018

Green onions and leeks have long roots – as far as their history goes, dating to 5,000 years ago. Most vegetable historians believe alliums like these originated in the Mediterranean region, although other members of the allium family started out in Asia. Any onion can be used as a green onion if it’s harvested before the bulb matures. However, if you want to grow the same green onions called scallions (or bunching onions) you buy at the market, plant the variety called Allium fistulosum. 

How to Grow Green Onions & Leeks


Green onions and leeks are grouped together because they have a lot in common. They look similar and can be grown in a similar way. Leeks look like giant scallions with their thick white stalks and long greens. Both are similar in taste, although leeks have a milder taste that makes them a favorite among discriminating cooks.


  • Prepare the garden bed so the plants will grow in a sunny spot, in rich well-draining soil. Add compost or well-aged manure and dig it in deeply to give roots an easier time getting started.
  • Look for short-season cultivars (50-70 days) that have some disease resistance to prevent problems while plants are growing.


  • Both onions and leeks can be planted from transplants or seed. For seeds, you can start them indoors, start them in cold frames or sow directly in the garden. Check the amount of time needed for plants to mature and start long-season varieties indoors well in advance of the last frost, which could be eight to 10 weeks before the last frost date.
  • If planting in the spring garden, wait for the soil to warm to about 50 degrees. Plant onion seeds ¼ to ½ inch deep; and onion sets or transplants 1 inch deep and 2 to 3 inches apart. Leeks need to be planted deeper,  4 to 8 inches deep and at least 4 inches apart. Rows should be 18-20 inches apart.
  • Add an organic mulch to help the soil retain moisture and to avoid weeding around the delicate and shallow roots.
  • For a continuous crop of green onions, keep planting onion seeds or transplants every few weeks, keeping in mind the time to maturity with the timing of cold weather.


  • Water is important for both scallions and leeks, and soaker hoses make it convenient to keep the soil consistently moist. Avoid soil that’s too soggy or too dry. It’s important to keep the leaves dry to prevent fungal problems.
  • The long white stalks of both vegetables can be encouraged by slightly hilling soil around plants when their tops are 4 inches tall. Continue hilling leeks at intervals to ensure long white stalks.
  • Add a well-balanced fertilizer while plants are growing to ensure healthy plants. Row cover cloth can help protect plants from onion flies that lay eggs that grow into maggots.


  • Smaller artichokes are typically more tender than larger globes. There will be
  • Carefully dig green onions when the tops are crisp, bright green and 6 to 8 inches tall and the base is firm and white.
  • Harvest leeks when they have crisp, brightly colored leaves and when stalks are ½ to 1 inch in diameter with 5 or 6 inches of white stem. Smaller leeks will be more tender than larger ones. Be sure to clean leeks thoroughly before cooking. First, trim the roots and leaves, then slit the leeks all the way down one side. Rinse to remove soil hidden between the leaf layers.

Companion Plants

Plant Green Onions, Leeks and Scallions with the following companion plants:

  • Beets
  • Cabbage family members
  • Carrots
  • Lettuce
  • Parsnips

Avoid planting near beans or peas

Materials for Success

  • Soil thermometer
  • High-quality compost and manure
  • Dry, balanced fertilizer (5-10-10)
  • Soaker hose
  • Row cover cloth
  • Garden fork for harvesting

To learn more about growing green onions or about growing your own edible vegetable garden, contact the pros at Nick’s Garden Center. 

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