What should not be planted near leeks?

Losing a crop of leeks due to stunted growth, I backtracked my grow space and noted nearby bean vines. Allelopathic plants such as beans release compounds from their roots that inhibit neighboring crops. Leeks were particularly sensitive to these lurid battles because their roots are shallow, which is also why they absorb inhibiting compounds more than a deep-rooted plant will.

Carrots are a great companion to help repel leek moths from coming after your leeks, as their feathery roots inhabit different soil depths altogether than the leeks. I space them 6 inches (15cm) apart - close enough for the carrot's scent to deter pests, but far enough apart that they won't limit growing potential due to competition. I make sure to rotate my beds every year to avoid repeated cycles of disease.

Soil management is far more effective than separation, even though we need to plant close to beans. If I have no choice, I take 45 cm (18 inches) of roofing felt and dig a trench around the plot. I apply compost tea weekly to lessen the impact of the allelopathic chemicals. The soil pH also must be monitored regularly. Monthly tests of 6.5-7.0 pH will allow leeks to grow at a pace that can allow them to outgrow the inhibitors.

Container gardens provide an alternative to traditional gardening. Plant strawberries in a 5-gallon bucket and place it right beside a leek bed. You can support peas on trellises and position the bucket with the strawberries about 4 feet (1.2m) from the leeks. That is the same arrangement I have on my balcony. It allows me to produce fat leeks, which is a narrow strip of growing area. The main concern here is airflow, more so than distance.

Read the full article: How to Grow Leeks: Beginner's Guide to Sweet Harvests