Blackcurrants and plum trees

[knbsallotment]

Bizarre and basic questions, especially from someone who has been growing veg for many years (but not much fruit - and I know nothing about fruit trees!)

How do I care for a VERY well establishes plum tree? Probably at least 15 - 20 years old?

Also, with blackcurrants (again very well established) - I am aware you need to cut them back by about a third, but how do I know which to cut back? Old growth or new?

Thanks

[knbsallotment]

[tonybloke]

blackcurrants, cut out a 1/3rd, old wood to be removed, they fruit strongest on new wood! delay pruning plums 'til the sap is running, this helps to stop fungus ingress.

[knbsallotment]

Excellent. Thanks for that. Stupid questions I know - but didn't want to destroy my blackcurrants - or me plums come to that!

[Robert_Brenchley]

When it comes to the plum, totally ignore everything you hear about winter pruning. They always say you shouldn't do it, but I had it from an expert recently, when I was on a pruning course, that every nursery prunes plums in winter, and they don't get silverleaf!

Pick a couple of branches, and cut them back to about 1 1/2 to 3 feet. Repeat every winter until they've all been done. If you do this in winter, all the goodness has been taken out of the leaves before they fell, and is stored in the roots ready for spring. The result is, buds will appear on the stumps, and grow like mad. Rub out all but about three, and let these grow on to become the replacement branches. By the time you've finished, you'll be well on the way to having a rejuvenated tree.

[tonybloke]

When it comes to the plum, totally ignore everything you hear about winter pruning. They always say you shouldn't do it, but I had it from an expert recently, when I was on a pruning course, that every nursery prunes plums in winter, and they don't get silverleaf!

Pick a couple of branches, and cut them back to about 1 1/2 to 3 feet. Repeat every winter until they've all been done. If you do this in winter, all the goodness has been taken out of the leaves before they fell, and is stored in the roots ready for spring. The result is, buds will appear on the stumps, and grow like mad. Rub out all but about three, and let these grow on to become the replacement branches. By the time you've finished, you'll be well on the way to having a rejuvenated tree.

superb explanation Robert! (not the sort you find in most books) ;D ;D

[jesssands]

what time of the year would you prune back the blackcurrent? and if I try and root a bit of it to make new bush, whens the best time for that please?

[tonybloke]

Usually blackcurrants are pruned at / soon after harvest. cuttings are usually taken from 1year old wood (brown, not green) when the leaves fall (mid - oct ish)  only take cuttings from really healthy bushes, if it is not healthy, you are only propagating bad / virus infected genetic stock.

[jennym]

When it comes to the plum, totally ignore everything you hear about winter pruning. They always say you shouldn't do it, but I had it from an expert recently, when I was on a pruning course, that every nursery prunes plums in winter, and they don't get silverleaf!

Not sure about that one Robert. Silver leaf is a nasty fungal disease, and ADAS reports for 2006-7 show that the incidence is increasing. I think that like all fungal diseases it takes a grip when the weather conditions, i.e.temperature, humidity etc are favourable for it, and for silver leaf, wetness is one of those factors along with the production of spores which takes place over the winter months. I know there's a few who routinely apply a fungicide when pruning to try and control it.

[Robert_Brenchley]

You always get an increase in fungal diseases in a wet summer, and we've just had two. Seriously, when do nurseries prune their top fruit? If they can do it in winter, so can we. The sort of pruning that's needed here is most definitely a winter job, if it's done in summer, the tree will just bleed like mad.

[jennym]

I do agree on your method for regenerative pruning for plums, it works well. Most of the orchards round here just take the old trees out completely so avoiding the situation of pruning, but if they do have a go at serious branch pruning in winter, say on younger trees that have suffered damage, they do seem to use wound paints. I don't know of any commercial orchards that go to the bother of regenerating old trees to be honest. I think it's more of a home garden/allotment situation.
The thing about silver leaf fungus as I understand it, is that the fungus fruits on dead wood in autumn and spores are produced over the winter period during periods of high humidity, and the number of spores produced rises during darkness and lessens when the temperature rises.
The fruiting bodies survive for about a year but by the time summer comes they have aged so that less spores are being released, and also the hot weather reduces the amount too.
So logically if there are more spores about in winter, the chance of infection is higher. Another thing to bear in mind is locality, some areas evidently don't suffer as much as others - maybe due to host population (it doesn't just affect plums), maybe due to climate, wind and so on.
As an aside, there are signs of the use of strains of this fungus as a biological control in the form of a stump paste in some countries to control the growth of some unwanted species, the stuff is sold as Myco-Tech. Hope it doesn't get licensed here.

[Robert_Brenchley]

I've been advised to avoid paint on the wounds. It seals the moisture in, and creates an ideal environment for fungal spores.

[jennym]

But if the wound is sealed, and the spores can't get in, how is the environment created....?
It's amazing how the advice given by the experts differs  :) One chap I knew, who was excellent with top fruit, did struggle a just a little when it came to giving a demo on forcing rhubarb using large pots and straw, he had to go and check that they should actually be covered up, he didn't quite believe it I think  ;D

[Robert_Brenchley]

You're quite right that experts differ! It shows how much evidence there is (or isn't) to back up a lot of what they say. The idea of not painting the wounds is that if spores land on the wound before the paint gets there, they're just given a nice environment to grow in.