How do they know? Because they do, they know. They know when I've mentally moved them to the "not sure they're earning their keep" side of the garden ledger. The first time this happened was in 2009 and I stumbled upon a much smaller Magnolia macrophylla with a flower bud. I left thinking, why hasn't my magnolia bloomed yet! The next morning I spotted the first ever bud on Clifford, our big-leaf magnolia. Coincidence? I think not.
My Clematis tibetana var. vernayi has been an extremely vigorous grower this year but without buds or blooms. Once it started to overrun the adjacent scheffleras (S. delavayi pictured here, but it's also tried to strangle the S. taiwaniana) I started thinking maybe it needed to go. After all the flowers are why I wanted this plant. No flowers = no point.
This is what I saw when we returned from vacation...
The entire plant is convered with green buds and yellow flowers.
How did it know?
The flowers are so "squish-able" they beg to be taken between your fingers and squeezed. Of course they bounce back, if you don't squeeze too hard.
This another of those plants that knew. Usually I garden for the foliage but occasionally I buy a plant just because the flowers rock. Such was the case with this Abutilon 'Red Tiger' - I wanted flowers! All summer it's grown like mad, but I've seen maybe, MAYBE, 3 flowers. Now there are 7 and buds everywhere. Just when I'd decided if winter didn't kill it it was still outta here.
Yes they do.