I bought a blue orchid last year. The flowers were beautiful and lasted several months. After the plant stopped flowering, I continued to follow the growing instructions (average light, watering when the soil was dry, etc.) and I was thrilled to see a new stem start to grow. There are 6 buds so far and I think there are more to come! But I was so disappointed when the first flower opened: it was white, not blue! What fertilizer should I give my plant to get the blue color back?
The color blue is not the strong point of orchids. They come in all the colors of the rainbow, but in the entire world, there is only one species that has truly blue flowers (Thelymitra crinita, the blue lady orchid, an Australian terrestrial orchid that is very rarely cultivated). Even the famous blue vandas (hybrids of Vanda coerulea) so often seen in orchid shows are not really blue, but shades of violet and purple.
The “blue orchids” you see in garden centres are actually artificially colored Phalaenopsis orchids. If a blue dye is injected into the flower stem of a white phalaenopsis just as initiates flowering, dye will travel to the flower buds and flowers will be blue when they do open.
This is how growers create the orange, lime green and bright yellow phalaenopsis also seen in the trade. You’ll also find blue Dendrobium orchids colored the same way in florist shops.
While this technique may be debatable from a horticultural point of view, it doesn’t actually harm the plant. However, it is certain that the next time the plant flowers, it will give only white blooms, because there is no artificial color in the new flower stem that is developing. Think of it like being when you dye your hair: sure, it will take on a new color, but the old color returns when your hair begins to regrow. With blue orchids, the original white shade (white phalaenopsis are used because they take on a purer blue color than more darkly coloured phalaenopsis) will return when they rebloom.
The blue dye needed to color an orchid is not available to home gardeners. Besides, the growers that color orchids have no desire to share their technique with us: they want to keep it secret.
But is it really that disappointing to have a beautiful white-flowered orchid? In your place, I’d be proud of the success I’d had in getting my phalaenopsis to bloom again and would appreciate the months of flowering yet to come. And if you absolutely must have a blue orchid, I suggest you simply buy another one.