All types of fennel plants are root-forming and prized for their licorice-like flavor. Utilized medicinally and as a culinary favorite, all parts of fennels are edible, including the roots. Though sweet fennel is highly desired, no matter the species in your garden, optimal growing conditions of roots are a result of appropriate care of the entire plant.
Plants provided with the proper growing conditions remain vigorous and have a greater capacity for fighting off disease and pests than weakened plants. Fennel roots thrive due to holistic care, or, the attention to all parts of the plant that results in optimal health of the whole plant.
As the roots of the fennel plant are the part of the plant that remain underground, soil conditions promote the health of those visible plant parts that remain above ground. Appropriate growing conditions yield a healthy-looking plant. Your fennel should reach a height of 4 to 6 feet with fragile radial expanses of vivid green foliage and small yellow flowers. Poor growing conditions often result in stunted growth and dull color.
The most successful fennel root development occurs when you provide the appropriate culture for your plant. Plant fennel in locations that offer full sunlight. With a preference for cooler temperatures in an ideal range of 70 to 75 degrees Fahrenheit, fennel thrives in well-drained loam soil, according to the Washington State University Extension Island County.
If your fennel roots are in soil often saturated with rainwater or that has poor drainage, change these conditions immediately. Waterlogged soil can result in the quick decline of plants and creates a prime environment for the collection and germination of fungal disease. Plant your fennel in a raised bed or amend your soil for increased drainage.
Consider the addition of mulch to your home garden for best fennel root growing conditions. Add organic mulch such as compost, pine needles or bark to the area surrounding your fennel in a layer measuring 1 to 2 inches in height, according to the NC State University Cooperative Extension Service. Mulch aids in beneficial water retention and inhibits the growth of invasive weeds that lead to diminished health of your fennel plant.