Grape varieties

Kerner: a variety the regulation names by its parentage

Ontario's wine regulation records one accepted synonym for Kerner, and it is not a name at all — it is the cross itself, "Trollinger x Riesling". For a grape bred in a laboratory in 1929, that is an unusually honest piece of labelling law.

The synonym

Table 1 of Appendix B of Ontario Regulation 406/00 lists 90 Vitis vinifera varieties, each with its accepted synonyms. Most synonyms are what you would expect — Pinot Gris carries Pinot Grigio, Lemberger carries Limberger and Blaufrankish, Syrah carries Shiraz. Kerner's is Trollinger x Riesling: the formula for how it was made.

The regulation does the same thing in two other places — Müller-Thurgau carries "Riesling x Sylvaner", and item 62 is simply "Riesling x Traminer", with a clarifying subsection specifying that it means the particular selection Riesling x Traminer 25/4. These are grapes from the great era of German crossing programmes, and in each case the cross was for a long time the only name the trade had.

What it is

Kerner was bred in 1929 at Weinsberg in Württemberg by August Herold — the same station and the same breeder who later produced Dornfelder — from Trollinger, a red grape, crossed with Riesling. It is named for Justinus Kerner, a local poet and physician who wrote drinking songs, which is a more charming derivation than most varieties manage. It was released commercially in 1969 and became one of Germany's most planted whites.

The aim was a Riesling-like wine on a vine that was easier to grow. Kerner buds later than Riesling, which keeps it clear of spring frost; it ripens reliably; it is winter-hardy by vinifera standards; and it keeps high acidity with a faintly muscat-scented aromatic character of its own. In a province where Chardonnay's early bud break is a genuine liability, late budding is worth real money.

Priced with the serious whites

The 2026 Grape Growers of Ontario price schedule puts Kerner in class 9a at $1,674 a tonne, grouped with Auxerrois and Scheurebe. That is above Riesling's $1,468 plateau price and just under the $1,868 paid for J. Riesling — so Ontario pays more per tonne for the imitation than for the plateau price of the original.

The class is a coherent grouping: three aromatic, cool-climate, German or Alsatian whites, all grown here in small quantity. None of the three reaches the top twenty by acreage in the Agri-Metrics study covering 2018 to 2022, and none registers in the reported LCBO varietal sales table.

The residual ripeness rule

Appendix A gives Kerner no line of its own, so it falls under "Other vitis vinifera varieties" at 17.0° Brix provincially and 18.0° for an appellation wine. That happens to match Riesling's provincial figure exactly, which is fitting for a grape bred to stand in for it — though Riesling's appellation figure stays at 17.0° where Kerner's rises to 18.0°, one of the few places the regulation is stricter with the copy than the original.

The other side of the family

The Trollinger half of the cross is the part that surprises people. Trollinger — the same grape Italy calls Schiava and Germany grows for pale, light reds in Württemberg — is a red variety, and Kerner is white. A white grape from a red parent is not unusual in breeding terms, since skin colour is carried by a small number of genes, but it makes the cross look stranger on paper than it is.

What Kerner actually inherited from Trollinger is vigour and reliable cropping; what it inherited from Riesling is the acidity and the aromatic profile. The combination is the whole point: Riesling's character on a vine that behaves better. Herold's later work at the same station produced Dornfelder by the same method of combining a workhorse with a quality parent.

Why so little of it

Kerner's problem in Ontario is not agricultural. A late-budding, winter-hardy, reliably ripening aromatic white is close to an ideal specification for this province. Its problem is that it is unknown: consumers who want a cool-climate aromatic white in Ontario buy Riesling, which the province has spent forty years establishing, and a grower planting Kerner is betting on a name with no recognition against one with a great deal. It is the same ceiling its class partner Auxerrois runs into, and the same one Zweigelt meets among the reds.