Basil is the most popular culinary herb grown in gardens, but with increased reports of diseases like downy mildew and fusarium wilt, it’s not always easy to grow. Growing disease-resistant cultivars, spacing plants to allow for air circulation and watering them in the morning to give foliage time to dry before nightfall are all steps you can take to encourage a healthy basil crop.
Downy mildew is a recent disease that first appears as a yellowing on the lower leaves of the plant. Soon, a dark gray fuzz coats the bottom of the leaves and brown patches appear. The disease spreads quickly, especially in damp weather.
The vigorous, compact and super-slow to bolt ‘Everleaf’ offers intermediate resistance to downy mildew. The plants grow up to 18 inches tall with heavy branching and short internodes, or spaces between leaves. That means plenty of aromatic fresh basil leaves all summer long. ‘Everleaf’ was also the last basil to flower, or bolt, in my garden, with blooms not showing up until late August. (Leaf flavor declines once the plant bolts.) Impressive!
I love the tall, dense form of ‘Pesto Party’, another variety tolerant of downy mildew. It grows about 24 inches tall and 18 inches wide. The medium-size leaves are aromatic and flavorful and the plants are very slow to bolt.
Fusarium wilt has been around a bit longer than downy mildew. Brown cankers show up on the stems and eventually cause them to wither and flop over. The foliage then dies.
‘Newton’ is an Italian large-leaf cultivar with intermediate resistance to fusarium wilt. Expect a classic basil flavor and leaves up to four inches long! The mounding plants grow 20 inches tall.
‘Newton’ is slightly later to flower than ‘Nufar’, a large-leaved cultivar that’s been around for a few years and has become a favorite of many gardeners. It has a typical basil flavor with hints of licorice and shows good resistance to fusarium wilt.