Can I plant a lilac in Toronto in April, or is it too early?
Lilacs should be planted either in the spring (once the ground is no longer frozen) or in the autumn before the ground freezes. As it is now April 23, the ground should be workable, so you can go ahead and plant the lilac. If we have another frost, this may affect the leaves or buds, but should not harm the plant.
Choose a spot with good soil drainage and lots of sun – at least 6 hours a day. Sunlight is critical in ensuring that you get the most blooms – with plenty of sun, the lilac will set flower buds that will bloom the next spring. If there’s too much shade, the number and quality of the flowers will suffer.
For an excellent & comprehensive overview of lilacs and their care, see the University of Wisconsin Extension’s Lilacs for cold climates.
Enjoy your lilac!