You can get grass to grow well in the shade.
No you can’t. Grass will put up with a lot; how any plants will put up with being regularly cut down and walked all over? Like everything it has its limits and it is never happy in shade, needing full sun to do well. What about shade “tolerant” grass seed varieties you say? Yes, some grass is more tolerant of shade than others; but that’s not the same as happy in shade. If the shade is slight these are probably a good idea, but once you start to get under trees and the like you cannot expect them to be any better than any other grass.
Garden ponds need a filter.
Properly designed and planted a garden pond does not need a filter. Long ago when I was a child we had a garden pond, along with many other people of course, but no one had a filter on them. This was for a good reason; they didn’t exist for garden ponds. What changed things was when people in this country discovered the hobby of keeping Koi fish. These fish are large, colourful, expensive thugs that dig up any plants growing in the pond. This meant people wanted ponds with just the fish in them but the fish could not survive in these conditions so Koi keepers invented the pond filter. This allowed pond water to be artificially kept very clear so people quickly realised it was easier to fit one of these to the pond to get clear water without the fuss of making sure the pond was properly planted up.
Parsley seed must be soaked before you sow it.
Some plants seem to attract myth and superstition and parsley is one. The truth is parsley is slow to germinate and gardeners can be impatient, so people have looked to ways to speed things up. To this end it is often said you need to soak parsley seed to get it to germinate; however it will germinate without any soaking. What if any difference soaking makes how quickly it germinate I do not know, but have you ever tried to thinly sow wet seeds? You can’t, they just form a wet clump.
Personally, I just scatter the seed over a patch of fine earth and water it just as if were grass seed and wait. In a few weeks it starts to germinate and once the first true leaves appear you can easily spot what parsley and what isn’t so you can weed and thin as needed.
You must water Rhododendrons, Azaleas and Camellias with rainwater.
I’ve heard this many times in hard water areas, based no doubt on the fact hard water contains lime and lime is used to reduce the acidity of soils and composts. While it is true Rhododendrons and other ericaceous need acidic growing conditions the amount of lime in the hardest drinking water, such as my local one, is not going to be sufficient to effect the plant you are growing. Nurseries and garden centres large and small happily grow rhododendrons etc. and I have never come across one that didn’t use the ordinary tap water regardless of how hard or soft it is.