Q: Can you recommend the best varieties of asparagus and the best time to plant? --Nancy Meyer, Lake Bluff A: Good varieties to consider include 'Jersey Supreme,' 'Jersey Knight' and 'Jersey Giant.' These all-male varieties offer good disease resistance and are winter hardy in Zone 2. Asparagus has separate male and female plants. Male plants provide a bigger harvest because they don't need to devote energy to producing seeds. And because they don't have seeds, male plants won't produce "volunteer" seedlings. Seedlings (and weeds) are difficult to remove without damaging the thick, matted roots of asparagus and will reduce harvest size if they're not removed. Importantly, these varieties are resistant to rust, a fungal disease that commonly affected asparagus before resistant varieties were developed. Disease-resistant plants are less likely to develop rust or need preventive applications of fungicides. Many gardeners prefer to plant dormant crowns rather than seeds. In this case it's also important to buy "disease-free" roots that are not infected with fusarium wilt (a soil-borne fungus that stunts the growth of spears and leaves and causes underground lesions). Newer varieties are tolerant of this disease. Asparagus crowns can be planted one month before the average frost-free date. In our area this means planting in mid-April. Best results occur in full sun where carefully prepared soil is well drained, organically rich and has a pH of 6.0 to 7.0 (slightly acid). Asparagus take patience but delicious results will make it worth the wait. A limited harvest is recommended for the third season. By the fourth season the established root system should be strong enough to provide an eight-week harvest of tender green spears beginning in May.
Robin Carlson, Chicago Botanic Garden