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Onion Fertilization and Care - Solution Guide

Onions are considered heavy feeders.

Broadcast 3-5 lbs. per 100 sq. ft. of Espoma® all-purpose 10-10-10 fertilizer OR apply an all-natural 3-5-3 like Dave Thompson's Healthy Grow Vegetable food at the same rate into planting beds. Cultivate this in and water well.
In USDA zone 5, this is typically done in March or about 4 to 6 weeks prior to planting.
Plenty of additions of organic material prior to planting is also always beneficial.

After planting

Once onion plants are growing, around the beginning of June, the rows can be side-dressed.
For this, use a 3-5-3 at a rate of 1 cup for every ten feet of row.

NOTE: Along with fertilizing, consistent watering during the growing season is essential for the proper growth of onions, as with any vegetables.

Limiting competitive weeds is important for achieving big onions, but remember, onion roots are shallow and sensitive to disturbance. Onion roots grow wide rather than deep.

Frequent and thorough hand-pulling weeds are best, rather than heavy-handed mechanical cultivation with a hoe or rake.