Prune your walnut trees on Saint Swithin’s day

Saint Swithin window at York cathedral
Saint Swithin window at York cathedral

It is Saint Swithin’s Day today, 15th July: the day on which people traditionally watch the weather.  Tradition says that whatever the weather is like on St. Swithin’s Day, it will continue the same for the next forty days.

There is a well-known weather-rhyme in Britain:

St. Swithin’s day if thou dost rain
For forty days it will remain
St. Swithin’s day if thou be fair
For forty days ’twill rain nae mair.

St. Swithin’s Day is also the ideal time of the year to prune walnut trees.  Pruning walnut trees in the dormant season (i.e. when the leaves are absent) is not recommended as it is for nearly all other broadleaved tree species.  If a walnut is pruned when the tree is dormant, or even worse when it is actively growing, the pruned wound will bleed profusely which will weaken growth the following season, and possibly increase risk of infection.  Pruning is undertaken ideally near the end of the walnut’s active growing season and St. Swithin’s Day, in mid July, provides a perfect marker.

Gabriel Hemery

8 thoughts on “Prune your walnut trees on Saint Swithin’s day

  1. regarding walnut trees – I remembered this rhyme

    a wife, a spaniel and a walnut tree
    The more you beat them, the better they be.

    Which is very bad advice for training springers.

    1. Thanks Andy

      I agree about the dog! In relation to walnut though there are some believable theories that beating may be good for walnut for two possible reasons:

        Hitting the ends of branches may stimulate side spurs on walnut which can increase nut production … although careful pruning may be less damaging!
        Beating the trunk of a walnut may possible induce burr growth on the stem which of course is highly valuable. This is not proven though so I wouldn’t recommend it!

      Gabriel

      1. Hi Gabriel,
        interesting articles on green walnut pickles and pruning Walnuts.
        Have just bottled my first Nocino [ green walnut wine].I was a bit late [February] in picking the walnuts. I think here in South Australia they will need to be picked around end December or earlier if we have really hot weather. Will be waiting for Christmas so i can pick green walnuts to make my own pickles.
        As I live in South Australia i wonder when the correct pruning time is. Last year i did some before the tree was dormant and it did ‘bleed’ so i did some later when it was dormant.
        St Swithin’s is of course the middle of winter here ,which is when we harvest the nuts
        Regards Christine

        1. HI Christine and thank you for your comments and question. In terms of identifying the best time to prune walnuts in the southern hemisphere, you should aim to prune them when the main growth period has ended but before they are dormant.

          In suggesting July in the northern hemisphere, this is when their growth has slowed but the shoots are still live. Any pruning wounds are then sealed and will start to heal over (occlude) before the dormant season some two months later.

          Perhaps you can now identify which month this should be for you in South Australia and share it with other readers …?

          Thanks
          Gabriel

  2. Here in Derbyshire we have a most attractive walnut tree which must be about 15m high and 50 years old, and has occasionally produced usable walnuts though usually they drop off too soon (this year looks promising). It is a mature tree and doesn’t seem to be getting much bigger year on year. Can it be pollarded or at least cut back quite severely? It is going to be taking the sun off some solar panels we plan to install. I took a couple of lower branches off it 3 years ago (eg crown lifting) but would now need to reduce the entire crown quite a lot. Very grateful for any advice.

    1. Hi Edward. Thanks for your question. Yes walnut is remarkably tolerant of all sorts of abuse and will even coppice. Just ensure that you find a reputable arborist (check the AA or ICF for registered ones nearby) to do the work.
      Good luck
      Gabriel

Leave a Reply

Your email address will not be published. Required fields are marked *