Celery can be attacked by parsleyworms, carrot rust flies and nematodes, but these pests are more often found in huge commercial plantings than in home gardens. This is why commercial celery, or store-bought, is one of the most pesticide-laden crops in the produce aisle. Grow your own for worry-free, healthier celery with these tips. 

Parsleyworms are the larval stage of black swallowtail butterflies, so if you find any just transfer them to another umbelliferous plant, such as Queen Anne’s lace. Row covers on hoops over the plants will keep carrot rust flies away if you know they are likely to be a problem.

The best defense against nematodes is plenty of compost and crop rotation; avoid growing any of the carrot family plants in one spot more than once in three years.

What has gotten celery its finicky reputation is its intolerance of temperature extremes. When it is young, if the soil is too cool it will bolt. If it gets too much hot, direct sun, it will get tough and stringy, maybe develop hollow stems and then bolt. Its ideal conditions are cool days and nights, with moderate sun, in rich, cool soil.

• The key to success is to keep the soil consistently moist. Use drip irrigation regularly, and mulch with straw or shredded leaves to keep the soil moist and keep weeds away.

• Add plenty of well-composted chicken manure or alfalfa meal, for plenty of nitrogen in the soil, one or two weeks before seeding or transplanting.

• Avoid boron deficiency by adding boron to the soil or using a fish fertilizer drench. Boron deficiency shows up as dark spots on the stems.

• Weed celery carefully; the roots are small and shallow. It is better to cut a nearby weed off at ground level than to pull it out and disturb the celery’s root system.

Peter Garnham is a contributing editor to Horticulture.