Mychorrhizal fungi

Last year, I bought some soluble myco fungi in a box.  I'd never heard of it before.  I used it as directed to water the plants in the old GH border when planting out and when removing the old plants in autumn I was pleased to see lots of white fungi strands within the  soil, so the fungi was thriving, hopefully doing its job.    I will need to improve the border soil in the new GH but I'm loath to use the horse  manure I have, as it's very seedy.  I'll probably make manure tea with it and use it that way.  I have my own compost to incorporate as well and will give the plants a dose of fungi.
My query is, do I have to repeat treatment of the fungi each year or is it a one time thing? Should I dose the old GH borders at planting a second time?

Well I'm no expert but I thought it worked by attaching itself to plant roots. You don't water it into a border.
So the roots of roses etc need to be covered or sprinkled in the planting hole.
If you have plants that look like they need a pick me up, under plant with other plants and sprinkle those roots?

#edit; I've only used the granuals- the plants were soaked in a bucket and the roots throughly covered before planting.
I think I used a jel once too?

Well I'm no expert but I thought it worked by attaching itself to plant roots. You don't water it into a border.
So the roots of roses etc need to be covered or sprinkled in the planting hole.
If be you have plants that look like they need a pick me up, under plant with other plants and sprinkle those roots?

The box I bought was Q4 Vitax soluble and the instructions were to water in at planting with no mention of repeat treatments.  As you say, the majority of the products on sale are granular.  I suppose it's a case of 'suck it, and see'.  I only bought the box of soluble because it was the right price to complete the value of a voucher I needed to use up.

What are you growing in the GH borders?

I first used the MF when I planted new standard roses in a border, one had had a rose in before. So I planted in with the MF and fed the roses every year since with rose feed and some grow more on the rest of the border. I would say that they have responded well to the feed?
I haven't used MF again on those borders u til last autumn when I added in more roses.

It's expensive stuff so I have just used it when
I've planted in roses, shrubs or trees.

It probably depends on the product. I have some ericaceous feed that includes MF, and the instructions say to apply it once or twice a year as a top dressing. However AFAIK "straight" MF is generally only used once, when planting.

One thing I did notice was I watered some bedding plant in flats, they then of course went in the ground outside, when those plants were dug out in the autumn the soil surrounding them was white with mycelium, which I assume was good.

It probably depends on the product. I have some ericaceous feed that includes MF, and the instructions say to apply it once or twice a year as a top dressing. However AFAIK "straight" MF is generally only used once, when planting.

I think that is due to regular MF does not work with ericaceous plants? So it's not used at planting time.

Rootgrow state that one application at planting time with support the plant for its lifetime.

It probably depends on the product. I have some ericaceous feed that includes MF, and the instructions say to apply it once or twice a year as a top dressing. However AFAIK "straight" MF is generally only used once, when planting.

I think that is due to regular MF does not work with ericaceous plants? So it's not used at planting time.

Rootgrow state that one application at planting time with support the plant for its lifetime.

I also bought some ericaceous-specific MF for potting up my second blueberry bush - maybe regular MF doesn't work for them? Could well be different species, and maybe they aren't as long-lived as the alkaline-loving variety.

With my scientist hat on again, I can attest that there are a crazy number of fungal species (many of them hard to classify), so sticking with the manufacturer's instructions is probably your safest bet.