No its not, Bernard - Epsom Salts will do the trick.

Dolomite, if youre soil is too acid. Probably not common with Clematis!

Thanks, Bamboo. I am aware of the use of Epsom Salts, but no idea how much to dilute it and I am aware of the dangers of over-feeding. For that reason I would prefer a commercial product to use for general feeding that contains magnesium, hopefully in the correct proportions. I have found one, marketted by Vitax as a Clematis feed which contains magnesium, but it is pelletted and I much prefer a soluble feed. I'm not sure I understand the reason why some feeds are pelleted. While on the subject of feeding, I have been trying to locate Miracid and it seems to have disappeared from the garden centre shelves. Have you any clue about the situation?

Odd, still seems to be available on the net, Miracid that is. As for the epsom salts, Vitax make a feed for plants called Epsom Salts, in a box, with instructions for use. Regarding pelleted feeds, they're done this way so they break down slowly (rate of breakdown varies from feed to feed) and continue to supply the plant for a number of weeks, rather than a watered on diluted product which works instantly, virtually.

When Miracle Gro changed the formula of their All Purpose, they also changed the name and label of Miracid. You will now find it under "Miracle Gro for Acid Loving Plants". Considering Clematis and water-soluble feeds, how do you think Miracle Gro for Roses would do for Clematis, Bamboo? It has a fair amount of magnesium in it.

to be frank, Tugbrethil, I'd just use Epsom Salts, whether that was the Vitax garden version or the one for humans - its not something the plant will need all the time, specially clematis. As for roses, I always use a specialist rose feed on mine - usually Toprose, because they're balanced with everything a rose needs.

That makes sense, Bamboo. I prefer to use components, myself. People do keep looking for a one-size-fits-all product for their whole garden.

I have made enquiries of our local garden centres and they confirm that Miracid has been replaced by Miracle Gro for acid loving plants, a pelleted product. The Vitax product 'Clematis fertiliser' is also pelleted. I have a bit of a problem with this as it seems that the pellets can't just be scattered on the surface. The soil has to be raked or scarified to bury the pellets and this causes me some concern about root damage/disturbance. The roots of my Clematis are covered with pebbles to keep them cool and the pellets wouldn't stand much chance of reaching the soil. I water my Clematis about once a week if there has been no significant rain and give each plant a couple of gallons. Might it be a good idea to add a small amount of feed at watering time, maybe even dissolving the pellets in the water?

I wouldn't recommend dissolving them in water, Bernard, very hard to make a judgement about how much you're giving the plants. Don't forget, pelleted feeds are meant to break down over about 6 weeks (usually) and some are meant to be applied in Spring and provide enough nutrients for the whole season. I am, though, wondering why you feel it necessary to so regularly feed your clematis - if they're in the ground, they don't need it except perhaps in early spring.

Misunderstanding there. I give my Clematis a feed of Phostrogen in the early spring as you say, but somehow I got the impression you were suggesting that the magnesium supplement was needed on a regular basis. If this is also required only once a year, how about if I supplement the Phostrogen with Epsom salts? If you would be happy with this, could you perhaps suggest the amount of Epsom salts to be dissolved in a gallon of water?

Pass, no idea Bernard - were it me, I'd buy the Vitax garden version with instructions. Might be a clue on the internet though, I'll google it later when I've got time...

I usually use about a teaspoon per gallon, one gallon per foot of height or width of the plant, whichever is bigger.

Thanks for your advice and comments, but Bamboo, I'm really puzzled that as you recommend and presumably use Epsom salts, you have no opinion on the dilution to use. Do you just sprinkle the Epsom salts on the ground?
Bearing in mind the limitations on my use of pelleted feeds, I wonder if the best thing to do is add a couple of teaspoons of Epsom salts to my spring feed of Phostrogen diluted in two gallons of water.
As regards to watering, if there has been no substantial rainfall, I usually water each Clematis plant with two gallons of water every week. Any comments?

Well, first let me say that I have never in my life used epsom salts for any purpose whatsoever, which is why I don't know the amount you'd use for your purposes. I've never had a problem with magnesium shortage on any plants, but that might be because every year in spring, any gardens I look after get dug over and feed incorporated (Vitax Q4), every 2 years receive a mulch of something organic and composted (usually soil conditioning compost from the garden centre) and plants like roses get given a specialist rose feed. I know, though, that you have a much larger area than the average garden I care for, so would guess it may not be possible for you to institute such a regime. I would, though, recommend that you start using powdered or granular feeds - all you have to do is stir it into the soil by either pricking over lightly with a fork, or raking into the top inch or so. Done with care, no problems result from this procedure, and the feeds then take longer to break down and keep working for 6 weeks, usually. Adding a mulch afterwards, assuming the ground is moist, also ensures the feed is below the soil level. I then don't feed again for general shrubs and climbers, but will feed the roses a second time, and obviously, summer bedding gets fed weekly with a high potassium feed. I've been trying to find out what the composition is of Phostrogen - unfortunately, the page which might tell me appears to be inaccessible for the moment. I'm wondering whether, if you feed regularly with phostrogen and it has no magnesium (on your clematis) that might be why the nutrients are out of whack so to speak, and there's a magnesium shortage - the other nutrients are present in abundance from the phostrogen, meaning magnesium deficiency occurs. As I seem to have written an entire essay, please let me know if I've not answered your query properly...

Having reviewed your query and my answer, if you want to use the epsom salts in phostrogen, that dilution does fit with what Tugbrethil suggests, so that'll probably be fine, though I'd be more comfortable with agreeing if I could only find out the composition of Phostrogen. As for the pelleted feeds, as you've only got to do it once a year, can you not just move the pebbles/stones out of the way, apply the feed, stir it in, and then replace the stones?

Bamboo, after some difficulty I have obtained from the makers of Phostrogen the chemical anaysis of the fertiliser and am hoping I can copy it below if the GoY system can cope with it. That didn't succeed, so I wonder if you can let me know your e-mail address (Perhaps by PM) I could send you a copy.
However, I can tell you that Magnesium is included in the makeup of the feed and therefor I'm completely at a loss to understand why my Clematis plants are suffering from magnesium deficiency.
I'd appreciate your comments.

I've sent you a PM, Bernard.