Blue hydrangeas etc.

I am very fond of hydrangeas, especially blue ones.

About five years ago I was bought a blue hydrangea for Mothering Sunday, one large deep blue flowerhead - it looked magnificent. So when it had passed its best I planted it out in the garden and was determined to nurture it so that for many years I could admire the shrub.
To keep hydrangea blooms a blue colour they need an acid soil and since the garden soil is not acidic I bought some ericaceous compost,the right sort to use with acid loving plants, and filled the planting hole with it. For two years I watched in hope but the plant produced greenery and no flowers! Reading up I found out that hydrangeas flower on two year old wood and that by pruning it I had been cutting out the flowering stems!
The solution was simple - leave the plant alone. Since then there have been more flowers, each successive year.

When a flower head appears it is very pale green and whether it turns blue or pink depends on the composition of the soil. How do you keep a soil acid when it is naturally neutral to alkaline? Tea bags.
They add acidity to the soil so the hydrangea gets tea leaves (used ones that have been dried out and then emptied out of their paper pouch) on a regular basis. You can see they like the treatment.
When I was in Brighton recently, there were many pink hydrangeas in front gardens - the soil in that part of south eastern England is chalky and alkaline.

P.S. Why do cabbage white butterflies lay bright yellow eggs? They show up so easily that they are easy to deal with.