That's what this great forum is for! Don't apologise for asking....
As a general rule, the cause of no flowers can be:
- Pruning too hard. Most Hy's do, indeed, flower on the previous years growth. These are mainly the mop-head type (big, round fat flower heads). So for these varieties you prune the shrub after it flowers.
Some, however, (some of the lace-cap types or modern species) flower on the current seasons growth - in which case you prune in late winter or early spring when the shrub is dormant.
My fail-safe (!) method of pruning if my client or I don't know which variety - then you have 2 options: if you can't stand the sight of the manky flower heads in late autumn, you take the flower head off ONLY to the next pair of leaves down the stem. Otherwise, try and leave the flowerheads on over winter (this seems to protect the new buds) and take the flower heads off using same method in early spring once the weather warms up.
If you need to prune drastically to reduce the size of the Hy, again, do this in early spring but be prepared to probably lose that years flowers - but they usually recover in time. Don't take out more than 1 in 4 of the old stems ( the younger ones are more pliable and greener) at once and try to reduce the size over a 2 year period.
Pruning rules in gardening always have a 'but' !
Other causes of non-flowering:
Too much shade - Hy's need some sun to flower well.
Too much fertiliser, especially one high in Nitrogen - this is especially good for green, leafy growth - but not many flowers.
If you look on any fertiliser packet it will tell you the NPK ratio/percentage
N is Nitrogen - green, leafy growth
P - Phosphorous - good for root and flower formation
K - Potassium (Potash) - good for flowers, fruit, and general health & strenghth of plant.
So if you have been feeding with a high nitrogen, pop down to your local plant centre & get Sulphate of Potash ( much cheaper than branded names).
Having said that, any plant needs a balance of NPK - but this is more important in a pot than in the ground. If your soil is anywhere reasonable (ie a general purpose fertiliser and compost/manure added to the soil spring & summer) then usually the soil will give the plant all the nutrients it needs. Clay soil is generally more fertile/full of nutrients than a sandy soil - but, of course, a complete b******* to dig or improve.
Other causes of non-flowering are prolonged winters with heavy frosts. This kills the new emerging flower buds. I don't really see this as a big problem in this country - however this spring was very peculiar as it got very warm very early on (which made the plants spring into life) and then it got very cold with a few late frosts. Certainly this year all the plants I look after don;t know whether they are coming or going, and ther normal rules don't seem to apply.
