I have 2 questions to ask you regarding pruning.
1. I have several clematis growing, primarily Jackmani. I usually prune around this time before frost sinks in. Is this the correct time? They grow beautifully and see solid flowers during June and July, but I wonder if the timing of pruning bears a relationship to the length of time they blossom. I would like to keep them in bloom all summer if possible.
My 2nd question involves pruning of grape vines. I have a 4 year old rescue vine. Last year It produced an ‘honourable’ amount of grape clusters. This year I had a very measly 1 cluster! I think I was too aggressive in my pruning last spring and cut back too far. It did produce lots of branches and shoots and leaves but only one embarrassing cluster! Any thoughts? Is early spring the right time or fall? If I’m supposed to cut back this year’s growth, how far back should I go?
Thank you for contacting the Toronto Master Gardeners concerning the timing for pruning your Clematis and your grape vine. I have answered then one at a time, but it looks as though you are going to do your pruning of both vines when it is very cold!
A. Pruning your Clematis:
Clematis can be a confusing group of plants to prune, since they are not all pruned the same way. Clematis fall into three different categories, based on bloom time. They bloom on either last season’s growth or on new growth. Luckily, you know the variety of clematis you have.
The following information from one of our earlier posts describes the proper way to prune your clematis depending upon your variety. The Jackmanii variety of clematis falls into the third category and you should be pruning it in late winter or early spring. I think if you postpone your pruning until February or March, you will get a longer blooming period.
1) Early flowering clematis
Early flowering clematis typically bloom in April and May, from buds produced during the last growing season. Prune these plants immediately after blooming, but no later than the end of July in order to give the plant enough time to produce new buds for next year. Start by removing shoots that have bloomed. If necessary remove dead or damaged stems. If growth is congested then cut out older stems to the base and thin the rest. Avoid cutting far into the main woody trunks. Cutting off too much may affect next years flowering. This group includes C. alpina, C. macropetala, C. armandii, C. montana, and C. chrysocoma.
2) Large-flowered/mid-season clematis
Large flowered hybrids like ‘Nelly Moser,’ ‘Miss Bateman,’ Lasurstern,’ and ‘Duchess of Edinburgh’ bloom in mid-June on stems from the previous season and often will bloom again in late summer on new growth, though these blooms tend to be smaller. Remove dead or weak stems in late winter or early spring, leaving the best of last year’s buds. Once they finish blooming, deadhead all bloom stems or cut the plant back to 12-18” to force new growth for a second round of flowers.
3) Late flowering clematis
This group’s flowers are produced on the current season’s growth and are the easiest to prune. Some types begin blooming as early as June and continue into the fall. This group contains the greatest number of clematis. In late winter or early spring, cut the plant back to 24-36” since no old wood needs to be maintained. Varieties like C. ‘Jackmanii’, C. viticella, C. flammula, ‘Royal Velours,’ and ‘Duchess of Albany’ fall into this category.
B. Pruning of your grape vine.
Pruning of grapevine
Grapes bear fruit on the green shoots that arise from one-year-old canes. The old canes that produced fruit this season will not produce again. You need to prune back those old canes and nurture the new canes.
I have attached two links to sites you will find useful. This first one is from the University of Minnesota Extension. They say you should prune your grapevine in March: https://www.extension.umn.edu/garden/yard-garden/fruit/growing-grapes-for-home-use/
I have also provided a link to an OMAFRA (Ontario Ministry of Agriculture and Food and Rural Affairs) site. (http://www.omafra.gov.on.ca/english/crops/facts/info_grapeprod.htm#anchor39516;
The OMAFRA report is very detailed and is specifically directed to commercial grape growers, but the section on “Pruning and Training Systems” looks very good and has some useful illustrations around supports for the vines. The report says that, “Grape pruning seems drastic to the uninitiated. The bulk of the previous season’s growth is removed, leaving only four to six canes. These are reduced in length according to the vigour of the vines.”
As far as timing goes, OMAFRA emphasizes that pruning should be done when the grape vine is dormant. You should wait until at least next month (December) since we have not had a hard frost in Toronto yet. I am hoping you will be able to identify at least the kind of grapevine that you have since there seems to be a difference of when to prune depending on variety.
I quote: “Pruning can begin any time after the first hard frost (-5°C or below) and should be finished before the vines start to “bleed” in the spring. The important consideration is that the vines be thoroughly dormant. Pruning should not be done on very cold days when canes are very brittle and those left may be injured when pulling out the brush. Prune labrusca types (Concord, Niagara) first starting as early as mid December and after the first cold temperatures, then prune the French hybrid vines in mid winter and the vinifera vines last in late winter or early spring, as they are more likely to suffer winter injury.”
Good luck with your clematis and grape vine!