The star magnolia (M. stellata, Zone 5) is likely the most widely grown. This slow-growing shrub may eventually reach five metres tall and about three metres wide, with dense branches and 10-centimetre-wide, white flowers. ‘Waterlily' has pink buds with 14 petals each that open white, while ‘King Rose' and ‘Pink Star' both produce blooms with 22 pink-tinged petals. The most popular variety is ‘Royal Star', with pink buds and fragrant, white flowers that have up to 30 petals. It's also the hardiest and is worth trying in sheltered Zone 4 gardens.
The flowers of the saucer magnolia (M. x soulangeana, Zone 5) average nine petals and are much wider and larger-up to 25 centimetres across-than those of the star magnolia; inner petals overlap and form an almost closed chalice, while outer petals spread slightly to make a saucer. They're generally pale purple outside and white inside, but this varies. Like its blooms, the shrub is large-it can reach a height of 10 metres in good conditions. Growth is upright when the shrub is young but spreads as it matures. The saucer magnolia is a hybrid of M. liliiflora and M. denudata, and originated in the garden of Étienne Soulange-Bodin in 1820 in Fromont, France. He had been a cavalry officer in Napoleon's army and, following the defeat at Waterloo and sickened by the war, he turned to his garden for solace. As he wrote in an 1819 edition of the Gardener's Magazine: “It had doubtless been better for both parties to have stayed at home and planted their cabbages.” Other hybridizers have repeated this cross since then and there are now many varieties with flowers of varying colour and size.
Another group of popular magnolias is M. x loebneri, introduced in the early 1900s in Germany. Two later selections from this cross are especially well known: ‘Leonard Messel', the blooms of which have 12 petals flushed with pink on the outside and whitish pink with a central purplish line on the inside and ‘Merrill', which is exceptionally free-flowering, with 15-petalled, white blooms. Both are hardy to Zone 5. ‘Ballerina' has pale pink blooms with up to 30 petals. It's slightly hardier than the other two but may not be as readily available.
Three other species magnolias are solid choices for Canadian gardens: the Yulan (M. denudata, Zone 5b) is a large, rounded shrub or small tree that grows nine metres tall and has fragrant, white, cup-shaped flowers 15 centimetres across. It tends to bloom very early; if planted in an exposed location, its nine-petalled flowers may be damaged by a late frost. Kobus (Zone 5) becomes a large shrub up to 12 metres tall with fragrant, white flowers. This species doesn't bloom while young-a plant in my garden started from seed about 20 years ago has only just started to flower. Bull bay, also known as southern magnolia (M. grandiflora, Zone 7), is evergreen and flowers in late spring with occasional blooms throughout summer and fall. This large tree reaches 24 metres tall and spreads 15 metres across. Its dark green foliage often has rust-coloured fuzz on the underside. ‘Little Gem' is better suited to average-sized gardens-it grows only six metres tall and three metres across.