Dill (Anethum graveolens) and fennel (Foeniculum vulgare) are attractive, flavorful herbs that are easy to grow in Iowa gardens. Their feathery foliage adds texture to herb and vegetable beds, while their leaves, seeds, and stems enhance a wide range of dishes. Both belong to the carrot family (Apiaceae) and attract pollinators and beneficial insects to the garden. Dill is grown as an annual, while fennel is often treated as an annual in Iowa, although it is technically a biennial, only flowering in its second year, although it will occasionally flower in year one when it experiences stressful, hot, dry conditions.
With adequate sunlight, well-drained soil, and moderate care, dill and fennel are rewarding herbs for Iowa gardeners. Their ornamental beauty, culinary versatility, and value to pollinators make them excellent additions to home landscapes and vegetable gardens.
Types | Growing Conditions | Propagation | Care | Harvest & Storage | Uses | Potential Problems | More Information
Species, Types, & Cultivars
Dill
Garden dill is typically grown for its aromatic leaves, flower heads, and seeds. Some cultivars are best suited for seed production and others are intended primarily for leaf production. These types are often referred to as "slow-bolt." Shorter cultivars are also available for use in containers. Popular cultivars include:
- ‘Bouquet,’ a reliable variety for seed production and cut flowers
- ‘Fernleaf,’ a compact selection suited to containers growing only 18 inches tall and slow to bolt
- ‘Dukat,’ a strong-flavored selection that produces abundant foliage and late blooms
- 'Vierling,' a strong-stemmed cultivar whose flower/seed heads are particularily well-suited for cut flowers
- ‘Tetra,’ a bushy late flowering cultivar
Fennel
Fennel is available in two main forms. Herb, or sweet fennel, is grown for its leaves and seeds and reaches 3 to 5 feet tall. Florence fennel, also known as finocchio, is grown for its enlarged leaf bases, commonly called a bulb.
Herb Fennel
- 'Bronze.' a reddish-bronze leaf selection well-suited for ornamental purposes
- 'Purpureum,' a bronze-purple leaf selection that is ornamental
- and ‘Rubrum’ provide ornamental interest
Florence Fennel
- 'Finale,' an open-pollinated variety with large, flattened bulbs and bolt resistance maturing in 75-80 days
- 'Mantovorno,' an early variety maturing in 75 days
- 'Dragon,' an F1 hybrid that is bolt resistant and late to mature, maturing in 90 days
- 'Preludio,' a productive fennel with uniform bulb production and well suited for fall production, maturing in 80 days
- ‘Rondo,’ an F1 hybrid variety with good bolt resistance and uniform white bulbs maturing in 75-80 days
- 'Fino,' an open-pollinated fennel maturing in 80 days
Growing Conditions
Dill and fennel grow best in full sun. Select a location that receives at least 6 hours of direct sunlight daily. While both tolerate a range of soil types, they perform best in well-drained soils with moderate fertility. Avoid poorly drained sites, as excessive moisture can lead to weak growth and root problems. High fertility is also undesirable because it encourages excessive foliage with reduced flavor.
Propagation
Dill and fennel are propagated almost exclusively by seed. Seeds germinate readily when planted directly in the garden. Both herbs develop taproots and do not transplant well. Because of their taproot systems, starting plants indoors is generally not recommended.
Direct sow dill and herb fennel seed in the garden after the danger of frost has passed. Dill can also be sown a week or two before the average last frost date to get an early start. Successive sowings of dill every few weeks provide a continuous harvest of fresh foliage throughout the season. Both herbs often reseed naturally in the garden if seed heads are allowed to mature.
Florence fennel is best sown in the garden early to mid-summer so it matures in the cooler, shorter days of early fall. When planted right away after the first frost, bulbs mature in the heat of summer, which can promote bolting (flowering) that lowers the quality of the bulb.
Care
Provide consistent moisture during establishment and during extended dry periods. As with most herbs, dill and fennel grow best with about 1 inch of water per week from rainfall or irrigation. Fennel, particularly Florence fennel, benefits from even soil moisture to encourage tender growth and prevent premature flowering.
Apply mulch to conserve soil moisture and suppress weeds. Shredded bark, compost, or untreated grass clippings work well. Avoid excessive fertilization, as lush growth often has less flavor.
To extend leaf production in dill, remove flower stalks when foliage is the primary harvest goal. However, allow plants to flower if seeds or pollinator benefits are desired. You can produce higher-quality Florence fennel bulbs by lightly covering the base as they enlarge, which helps blanch the bulb and improve tenderness.
Harvest & Storage
Harvest dill leaves as needed once plants are well established. The best flavor occurs just before or as flower buds begin to develop. Fennel foliage can likewise be harvested throughout the growing season in the same manner.
For seed harvest, allow flower heads to mature until the seeds turn light brown. Cut seed heads and place them in a paper bag to finish drying. As the seeds dry, they will naturally separate from the flower heads.
Harvest Florence fennel when the bulbs reach about the size of a tennis ball. Lift the plants, trim the roots, and remove excess top growth. Bulbs can be harvested over a period of several weeks. This is beneficial since they don't store well long-term.
Fresh dill and fennel may be refrigerated for short-term storage. For longer storage, the foliage can be frozen or dried. Dry herbs in a warm, dark, well-ventilated location until crisp, then store them in airtight containers away from heat and light. Properly dried herbs retain their quality for many months. Store Florence fennel in a loosely tied plastic bag in the refrigerator for up to 5 days. Bulbs do not freeze well.
Uses
Dill leaves, flowers, and seeds are widely used in pickling. The foliage also flavors salads, soups, fish, eggs, sauces, dips, and vegetable dishes. Dill seed is commonly used in breads, vinegars, sauerkraut, and spice blends.
Fennel has a distinctive anise or licorice flavor. The leaves and seeds are used in fish dishes, cheeses, salads, and vegetable recipes. The stems can be used similarly to celery. Florence fennel bulbs are eaten fresh in salads or cooked by roasting, grilling, or sautéing.
In addition to their culinary uses, dill and fennel are valuable pollinator plants. Their nectar-rich flowers attract bees, butterflies, hover flies, and other beneficial insects. The blooms also provide food for predatory and parasitic insects that help control garden pests, while the foliage serves as a host plant for black swallowtail butterfly caterpillars. Both plants, especially the bronze foliage forms, are well suited for garden borders, and shorter varieties are good for containers. The fine foliage contrasts nicely with other ornamental plants, and the tall height allows it to be in the back of the border.
Potential Problems
Dill and fennel are generally trouble-free herbs.
Pests & Diseases
Aphids occasionally infest stems and flower heads, especially as plants begin to bloom. Aphids can be washed off with a forceful stream of water when they are noticed.
Powdery mildew may develop during periods of poor air circulation or excessive irrigation. Proper spacing and careful watering help reduce disease problems.
Self-Seeding
Both herbs readily self-seed and may appear in unexpected locations the following year if seed heads are left in the garden. While many gardeners welcome volunteer seedlings, remove unwanted plants before they become established.
Caterpillars
Black swallowtail butterfly caterpillars often feed on dill and fennel foliage. Although they can consume significant amounts of leaves, they rarely cause lasting damage. Many gardeners consider them a desirable part of the garden because they support native pollinator populations.
More Information
- Growing, Harvesting, and Drying Herbs
- Growing Herbs Indoors
- Growing Herbs in Containers
- Ornamental Herbs for Iowa
- Harvesting and Preparing Herbs for Exhibit (4-H pub)
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