According to the website, April.
"In winter the bare bones of The Gardens show the shape of things to come, with the gentle variance of texture and colour of the broadleafed evergreens and conifers, the berried trees and shrubs. Hints of spring come from early pansies and English daisies, polyanthus and primroses. The bright red of holly berries and pink blooms of heather are a welcome contrast to the grey of a winter day.
Against a backdrop of blossoming trees and shrubs - forsythia, jasmine, pieris and the early flowering Japanese cherries - early March lays a carpet of crocus, wallflowers and spring flowers. The last week of March is the height of the season for hyacinths and daffodils.
In April the results of the fall planting of more than 250,000 bulbs reach their peak. First with the gold of narcissus and daffodils then with the riot of colour from beds of tulips - Spring dons her mantle. Flowering cherries and plums, crabapples and some 30 species of other flowering shrubs join the display. Rhododendrons and azaleas start to show and the native dogwood is starting to bloom."
I gather it's been an unusually cold winter in Victoria though, so it may be a bit later.
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