Classifications
One of the earliest and most widely used classifications of lucerne cultivars has identified four groups based on flower colour, origin, winter hardiness, disease-resistance and other agronomic characteristics. The groups are
• Common group — contains pure M. sativa ssp. sativa types with purple flowers and limited winter hardiness.
• Turkistan group — contains M. sativa ssp. sativa types with purple flowers. The growth habit is shorter and more spreading than in other types. The cultivars recover more slowly after cutting, have more winter dormancy and are resistant to cold and bacterial wilt.
• Variegated group — members have variegated (purple and white) flowers and are probably hybrids of M. sativa ssp. sativa and M. sativa ssp. falcata. These are the winter-hardy types.
• Non-hardy group — members have adapted to short days and have a long growing season. They have an erect growth habit, and recover quickly after grazing or cutting, but are susceptible to injury from the cold, and bacterial wilt.
Lucerne cultivars have different reactions (winter-activity levels) to the shorter days and lower temperatures, which occur with the onset of the cool season. For example, cultivars in the more winter-active classes have longer active growing seasons and greater potential growth during the cool — cold season. These differences, measured in the autumn, form the basis for up to 11 winter-activity categories level 1 to level 11.
These categories may be contracted to six groups to encompass the diverse range of lucernes available commercially: winter-dormant class 3, semi-dormant classes 4 and 5, intermediately dormant class 6, moderately winter-active class 7, winter-active class 8 and highly winter-active class 9 or higher. The latter three groups are sometimes classified as non-winter-dormant. Note also that there are no commercial cultivars with winter-activity levels lower than three available in Australia.
Winter activity is measured using regrowth height in winter to give a rating between 1 and 11.
However, in south-eastern Queensland we often use a simplified classification comprising four of the six groups: winter-dormant, winter semi-dormant, winter-active and highly winter-active. Within each grouping there is a range of winter-activity levels. The distinguishing features of these groupings are:
• Winter-dormant activity class 3. This group is able to withstand very low temperatures for long periods. These cultivars have a distinct dormant period, triggered mainly by day length (hours of light in the day). Even in warm climates such as south-eastern Queensland’s, they make little growth in winter.
• Winter semi-dormant activity classes 3-6. These cultivars grow significantly more slowly in winter than in summer. Little growth is made for a short period in the winter months (but for a shorter period than for winter-dormant cultivars) or growth can be merely limited, depending on the climate or the genetic background of the cultivar. Autumn and spring growth is faster than for winter-dormant lines. Lucernes in this group are generally more leafy and have broader crowns than the winter-active group.
• Winter-active classes 7-8. Growth by these cultivars slows in midwinter but never ceases. Properly managed, yields are higher than those of the semi-dormants, and the recovery after cutting is much faster. Generally, the group is not affected by day length, and cultivars continue to grow provided the temperatures are cool to warm. In winter, these cultivars grow more quickly in Queensland than in southern Australia. Winter-active cultivars are more susceptible to cold than the previous two groups. They, and the highly winter-active lucernes, have narrower crowns than the previous groups and have a lower leaf density because of longer internodes, fewer tillers and bigger leaves.
• Highly winter-active classes 9 and higher. These cultivars recover most quickly after cutting and are the most productive in winter.
Growth patterns
Lucerne cultivars in southern Queensland will find growth rates fall from January to July — August, and rise again until December.
Climate influences the performance of cultivars. The influence of other factors, such as disease, confounds these field dormancy patterns.
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