The Mt. Baker lilac was introduced in 1961 by Canadian Frank Skinner, known for his cold-hardy lilac hybrids. The Hyacinthiflora lilacs were developed as crosses between the common lilac, Syringa vulgaris, and the hardy northern Chinese native, Syringa oblata. Mt. Baker probably owes its large leaves and incredible fragrance to its vulgaris heritage, while its dark red fall color, extreme cold-hardiness (Zones 2-3), and rounded form likely come from the oblata relatives. The hyacinthiflora name was given to these hybrids because early breeders thought the flowers resembled tiny hyacinth flowers.
Mt. Baker is a pure white single with intense fragrance–almost tropical, but not cloying. One Mt. Baker lilac can perfume an entire neighborhood. This lilac displays blooms even at a young age; and, once mature, the plant is covered in multiple blooms every year. Normally, Mt. Baker blooms one to two weeks earlier than other lilacs (French, vulgaris), but, this year, with prolonged cool spring weather, my Mt. Baker lilacs were only a couple of days earlier than neighboring varieties.
Syringa ‘Mt. Baker’ is a large plant, growing to 10′-12′ high at maturity. My plants are 8′ high by 7′ wide after five years, starting from a height of about 2′. The shape is also somewhat unusual for a lilac, since branches extend down to the ground, giving the plant a more rounded, rather than upright, appearance. This also makes Mt. Baker well suited for a large hedge, as it never appears leggy and blooms are not confined solely to the upper branches.
This particular lilac is said to be mildew resistant. In my experience, “mildew resistant” means that the plant doesn’t begin to show signs of mildew until August rather than July. I advise preventative treatment for powdery mildew beginning in June. As with all lilacs, make sure that the Mt. Baker is planted to receive excellent air circulation. Fertilization shouldn’t be necessary unless the lilac is planted in sandy soil. If you want to fertilize the plant, wait until bloom is completed and then apply a balanced fertilizer such as 10-10-10. Pruning should be done after flowering and no later than the first week in July.