Celeriac (Apium graveolens var. rapaceum 'Diamant')

Overview

Apium graveolens var. rapaceum ‘Diamant’, commonly known as Celeriac or celery root, is a unique garden vegetable cultivated specifically for its enlarged, turnip-like roots that possess a distinct celery flavor with added earthy notes. This cultivar, ‘Diamant’, is noted for producing a clean, white, medium-sized, and generally round root structure, making it appealing for culinary use. As a cool-weather crop, successful cultivation of Apium graveolens var. Rapaceum ‘Diamant’ relies heavily on consistent temperature management, as it struggles in prolonged heat.

While listed as having low maintenance once established, Celeriac requires diligent attention during its initial growth stages to ensure proper root swelling. Gardeners aiming for high-quality roots must provide rich, moisture-retentive soil and consistent feeding throughout the growing season. Although not commonly grown in all regions of the U.S., this vegetable rewards the determined gardener with roots that are delicious both raw and cooked, particularly when harvested after experiencing a few light autumn frosts.

Fast Facts

• Plant Family: Apiaceae
• Plant Type: Annual
• Hardiness Zones: USDA Zones 2-11
• Size at Maturity:
  • Height: 1.5-2 ft
  • Spread: 1.5-2 ft
• Bloom Time: Seasonal bloomer
• Bloom Description: Green, white
• Sun Exposure: Full sun
• Water Needs: Medium
• Maintenance Level: Low

How to Grow

Starting Celeriac requires planning, as seeds should be sown indoors approximately 10 weeks before the last expected spring frost date. Transplant starter plants into the garden only after all danger of frost has passed, spacing them adequately, about 8 to 10 inches apart, to allow room for root development. Apium graveolens var. rapaceum ‘Diamant’ thrives when planted in full sun, requiring soil that is rich, moist, and exceptionally well-drained.

Consistent care is paramount for developing the desirable swollen root base. Ensure regular fertilization and maintain consistent moisture levels through regular watering; applying mulch is highly beneficial as it helps conserve soil humidity and suppresses competing weeds. Be aware that this cool-season vegetable dislikes heat; optimal growing temperatures fall between 60-75°F. If temperatures consistently dip near 55°F or lower for extended periods, the plants may prematurely bolt (flower), which halts root development.

Roots of Celeriac generally require 3 to 4 months to mature. Harvest timing is flexible, but roots often achieve peak flavor following several light fall frosts. Properly refrigerated roots (33-40°F) can be stored for several months, and cellar storage may extend this duration up to 6-8 months.

Landscape Uses

As a root vegetable, Celeriac is primarily grown in dedicated vegetable patches, but its upright structure and substantial dark green foliage allow for interesting textural contrast if integrated near annual flowers in raised beds. The ‘Diamant’ variety, growing up to 2 feet tall, functions well toward the middle or back of a small vegetable border where its height can be utilized. Although grown for its harvest, the foliage offers a lush, deep green backdrop throughout the summer before the focus shifts to root development in the fall.

If space allows, growing Celeriac in large containers is a viable option, particularly if soil amendment needs to be tightly controlled. Ensure containers offer excellent drainage to mitigate the risk of root rot, a problem associated with overly saturated conditions. Since it demands rich soil, pair it culturally with other heavy feeders like brassicas or tomatoes in a crop rotation plan, though separation is important during active growth.

Standout Features

Flower Qualities

• Insignificant

Noteworthy Characteristics

Apium graveolens is the progenitor of vegetable crops like Celery and Celeriac (Apium graveolens var. Rapaceum). The roots of Celeriac taste distinctly like celery but possess additional turnip-like flavoring and are edible both raw and cooked. The specialized ‘Diamant’ selection yields a clean, white, medium-sized, round but irregular root structure and grows to about 2 feet tall with glossy dark green leaves.

Tolerances

• Aphids
• Earwigs
• Nematodes
• Celery worms
• Slugs

Potential Problems

Celeriac cultivation may be hampered by common garden pests such as aphids, earwigs, nematodes, celery worms, and slugs, requiring routine scouting and management. Fungal issues like early blight and late blight can also manifest depending on regional conditions and humidity levels. The most significant physiological risk is root rot, which develops rapidly if the soil remains overly wet or poorly drained; consistent watering is necessary, but saturation must always be avoided.

Frequently Asked Questions

What hardiness zones is Celeriac suitable for?

Celeriac (Apium graveolens var. rapaceum ‘Diamant’) is remarkably adaptable, thriving across USDA Zones 2 through 11.

How large does Apium graveolens var. rapaceum ‘Diamant’ grow?

This variety typically reaches a height between 1.5 to 2 feet tall, with an equal spread of 1.5 to 2 feet.

What sun exposure does Celeriac need?

For optimal root development, Celeriac requires full sun exposure in the garden.

When does Celeriac bloom?

It is a seasonal bloomer, producing inconspicuous green and white flowers.

Conclusion

Apium graveolens var. rapaceum ‘Diamant’ offers gardeners a unique, flavorful root vegetable that adds variety to the autumn and winter kitchen larder. Achieving success with Celeriac hinges on providing rich soil and meticulously controlling moisture while maintaining cooler growing temperatures. Before planting, verify your local frost dates and ensure your chosen location offers the required full sun and excellent drainage that this specialized crop demands.

Companion Planting

Selecting suitable neighbors is key to maximizing the health of Celeriac. Since it requires consistent moisture and rich soil, companion plants that share similar cultural needs but occupy different root depths are ideal. Consider planting beans or peas nearby; these legumes fix nitrogen, benefiting the heavy-feeding Celeriac throughout its development toward forming its edible root.

Avoid planting other members of the Apiaceae family close by, such as carrots, parsley, or dill, as they share susceptibility to the same pests and diseases, increasing localized outbreaks. Furthermore, because Celeriac is sensitive to stress that leads to bolting, intercropping with low-growing herbs that help shade the soil surface can aid in keeping soil temperatures stable during shoulder seasons.

Seasonal Care Calendar

Spring preparation should focus heavily on amending the soil with ample organic matter several weeks before transplanting the seedlings started indoors. Ensure the transplant site is sunny and the soil structure is loose and well-drained to encourage root expansion. During the summer months, consistent overhead watering is critical, especially when temperatures fluctuate outside the ideal 60-75°F range—mulching well helps maintain this crucial cool, moist environment.

As autumn approaches, shift your focus to moisture management just before harvest, avoiding excessive watering in the weeks leading up to digging to ensure the roots cure properly for storage. Harvesting after a few light frosts is recommended for the best flavor profile. For overwintering storage, carefully brush off excess soil (do not wash) and cure the roots before moving them to a location that maintains near-freezing temperatures, like a root cellar.