Q: I have a winter flowering jasmine, growing profusely on a 3m-high north-facing wall. For most of its six years, it has produced an abundance of flowers, from early November until March. During the recent summer, I took a lot of its stems, which had bunched at about 2m, and gently stretched them out along a series of horizontal wires. This November I can only see a handful of flowers (less than 10). Did my gentle summer manipulation cause this drop in flowers and if so, how? CD, Co Dublin
A: Hmmm, I agree that this is puzzling. Commonly known as winter jasmine, Jasminum nudiflorum is one of those plants that most gardeners would put in the “tough as old boots category”. Very hardy, vigorous and tolerant of a wide range of growing conditions, its bright, unscented yellow flowers typically appear intermittently on bare stems from November to March (hence its Latin species name nudiflorum). Often described as a climber, in fact it’s more of a lowish-growing, non-clinging scrambler that rarely reaches a height of much more than 2.5m.
Although it can be left to do its own thing, training winter jasmine against a series of horizontal wires as you’ve described is often recommended to stop this deciduous plant becoming too sprawling and untidy. As its flowers are produced on young stems that need to slowly ripen over summer, pruning it in spring immediately after the plant has finished flowering is also recommended to encourage the production of plenty of new, fresh growth. With well-established plants such as yours, this means using sharp secateurs to cut old flowered stems back to a strong side shoot or bud lower down the plant. For older or neglected specimens, where the plant has almost certainly formed a wiry thicket of old, tangled stems, it’s recommended that every year you cut roughly a third to a quarter of these back down to the ground along with any dead, damaged or weak stems.
Unless you handled the stems roughly (which doesn’t sound the case), I don’t think that spreading them out along the training wires caused the subsequent lack of flowers. But sometimes even healthy, well-established plants can drop their flower buds when enduring stress caused by drought, flooding, extremes in temperature or other sudden changes to their normal growing conditions (consider it the botanical version of humans fainting). In this case, the high temperatures and near-drought conditions of last May might be the cause of your problem, especially if your winter jasmine is growing in a very poor, dry, free-draining soil that’s lacking in organic matter. If so, then I’d suggest mulching around the base with some well-rotted manure and a few handfuls of slow-release organic fertiliser in spring. Another possibility, one occasionally reported by other gardeners, is that either grey squirrels or birds have stripped the flower buds off your plant, in which case the problem may sadly be ongoing.
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