Ericaceous fertiliser
Hi all, been having trouble with some of my shrubs not growing well. I’ve not had them long just under a year but the issue I’m having is that my skimmia and gardina jasmine kleim and jewel haven’t grown they have stayed the same size that they when supplied in 9cm pot. They don’t look like they are dying but I’ve noticed the leaves are slightly yellow and on the jasmines some of the leaves have gone crunchy. Possibly other reasons why this has happened but looking on the RHS website I can see that these plants like acidic to neutral soil, I know I tested the soil where the skimmia is prior to planting and it was neutral to alkaline. I’ve read up about nutrients being there for the plant but can be locked in the soil if not acidic enough, I have been fertilising every two weeks but with a general purpose liquid fertiliser and I from what I’ve read the best way to condition the soil would be to organic material and well rotted manure etc but I have a few questions:
1) fortnight feeding with ericaceous fertiliser-would this over time make the soil more acidic, the bottle only tells me the nkp ratio but assuming it must have sulphur or something in it as it says for ericaceous on the label. And from what I gather even if I’m putting enough npk into the area if the soil conditions are not correct the plant can’t use them.
2) I have been watering plants with tap water as I don’t have a water butt which from what I’ve read can add calcium and other plant no nos to the soil so I’ve bought a water butt, would it be advisable to place some pine needles in the water butt as I’ve read that these are good for acidifying the soil, my plants have been weed fabriced and mulched with slate hence why I’m looking for alternatives to manually mixing material into the soil. Would the pine needles Help the water become more acidic and would this benefit the soil changing it more acidic over time which would allow the plants to take up the nutrients better from the fertiliser?
I’ve put pics of the plants in question


1) fortnight feeding with ericaceous fertiliser-would this over time make the soil more acidic, the bottle only tells me the nkp ratio but assuming it must have sulphur or something in it as it says for ericaceous on the label. And from what I gather even if I’m putting enough npk into the area if the soil conditions are not correct the plant can’t use them.
2) I have been watering plants with tap water as I don’t have a water butt which from what I’ve read can add calcium and other plant no nos to the soil so I’ve bought a water butt, would it be advisable to place some pine needles in the water butt as I’ve read that these are good for acidifying the soil, my plants have been weed fabriced and mulched with slate hence why I’m looking for alternatives to manually mixing material into the soil. Would the pine needles Help the water become more acidic and would this benefit the soil changing it more acidic over time which would allow the plants to take up the nutrients better from the fertiliser?
I’ve put pics of the plants in question



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Posts
Skimias do tend to be slow starters but grow at a good pace when tended. Your main issue is that you're trying to make them happier just with liquid feeding and that won't be enough. As Beth Chatto kept on harping for a decades, you need to have the right plant in the right place, forever fighting the natural properties of your soil and light condirioy will just lead to frustration and lots of expense and hard work.
If the soil isn't neutral to acidic, forget it. You can't change the soil by just adding things to it.
As @amancalledgeorge says - having all that slate there isn't helpful.
Put it in a container with appropriate soil - not just compost, and keep it well watered, and ensure it also has good drainage. They need shade unless they have the right conditions at their feet.
I've no idea what a gardina or jewel jasmine is, so can't help with that, but those plants look very unhappy. It could be one of several things - bad drainage, over or under watering, wrong site etc.
Planting a tiny plant straight out isn't a good idea either, unless conditions are right, so they were probably planted far too soon.
What prep did you the area before planting?
I live in west central Scotland - not where that photo is...
Here's the RHS info on the gardenia https://www.rhs.org.uk/Plants/194367/Gardenia-jasminoides-Kleim-s-Hardy/Details
I am also worried about your constant feeding. If your neutral soil is locking out nutrients then dumping more nutrients on will not make it more available, the plant will drown in them, not being able to absorb them and will end up burning the roots and create yellow growth.
Newly planted plants don't need any feeding for the first 3 months, it is more important that the roots establish themselves first.
Too often growers encounter one problem, try to fix it and actually cause another problem doing so.
Just stick to acidifying the soil. Manure and leaves work especially well for this too and provide enough food for a year without having to guess if you are burning the roots with added fertilizers it might not even need while young.
You might think it needs energy to grow and yes it does, rainwater has nutrients in it, sun light provides energy, nutrients are important but as you have discovered it is far more important the plant can absorb them, however little that is. If it can't absorb any nutrients at all due to lock out it will grow stunted.
Once those plants are twice the size and developing lots of new leaves is when it will need energy. Now it just needs a bit of TLC and the right soil ph but too much sun could be an issue also.
also rain water in fairly neutral and good to use for acid loving plants, these plants hate our limey alkaline tap water which does no good for the soil either. I think your spot is a bit too sunny for these guys if you have to water them lots, it might be worth considering a differnt variety altogether..
I'm not sure why you've dug in grass clippings to improve the area, but even so, if it wasn't something as tough as a skimmia, it would probably have died off. They take quite a while to reach a decent enough size for planting out in a big border. I wouldn't plant something that small out unless it was filling a 3 or 4 inch pot, and even then I would wait until at least next month, when things are wanting to grow. I'm used to that here, as our season is later, but even in a milder area, planting early is always a gamble.
The soil you're aiming for should be healthy, free draining and crumbly. The addition of organic matter, every year, helps whether you have clay or sand. Compost - home made or purchased is also beneficial. Drainage will depend on what you want to grow, the same with the aspect - ie the amount of sun or shade a plant gets. All plants need regular watering for a while, unless you plant in autumn or spring and have a climate which has regular, persistent rainfall.
If it's jasmines you have - they like very different climactic conditions and aspects from skimmias. They won't like soggy, heavy ground for example.
I live in west central Scotland - not where that photo is...