As the nights draw in and the first frosts touch the garden, many plants begin to fade, leaving us with questions about what to do next. In this week’s Ask The Gardener, we look at roses that don’t quite settle after transplanting, hydrangeas that refuse to flower, tulips that vanish after a single season, and much more.
Below are the questions you sent in, along with my advice to help keep your garden looking its best this autumn.
Why is one of my transplanted roses failing?
Zeda in Kilkenny brought four established roses from Sligo to her new garden. Three have thrived, but one looks like it’s on the way out.
When roses are moved, they often sulk for a year or two before they settle. If one is struggling, cut it back lightly to reduce stress, water it well, and mulch around the base to protect the roots. It may well bounce back in spring. But if it fails to show signs of life by next season, it’s better to replace it with a healthy new plant.
Should I deadhead a young mophead hydrangea?
Nuala’s mophead hydrangea is full of brown, spent blooms. The instinct is to snip them off, but don’t be tempted just yet. Those faded flowers act as natural insulation, protecting the developing buds beneath from frost damage. Leave the old heads on through winter, and prune them back to a strong pair of buds in spring.
Why didn’t my hydrangea flower this year?
Raymond’s hydrangea didn’t produce a single bloom. There are two common causes for this: pruning at the wrong time or frost damage. Hydrangeas form their flower buds on last year’s wood, so if you prune in autumn or winter, you cut off next season’s display. Equally, a late frost in spring can blacken young buds before they open. To improve flowering, feed your plant with a potash-rich fertiliser in spring and avoid cutting it back until the risk of frost has passed.
Why do my grapevines never produce grapes?
Norman has two vines but no fruit. Grapevines need plenty of heat and sunshine to ripen properly, which can be a challenge in the Irish climate. They also require very specific pruning each winter, cut back too little and you’ll have masses of leaves but no grapes, cut back too hard and you risk weakening the plant. For reliable crops, vines are best grown under glass in a greenhouse or polytunnel, where you can control heat and ripening.
Can I cut back my lacecap hydrangea now?
Tracy in Kerry is keen to tidy her lacecap hydrangea before winter sets in. Hold off for now as pruning hydrangeas in autumn exposes young buds to frost damage. Instead, wait until spring, then remove dead or damaged wood and cut back the old flower heads to a strong pair of buds. Light pruning is best, as heavy cutting reduces flowering.
What plants work best in winter window boxes?
Pauline from Newtownards wants colour for her winter boxes. Choose hardy bedding plants such as winter pansies, violas, cyclamen, or primroses, which all cope well with the cold. Add evergreen structure with ivy, skimmia, or dwarf conifers. For an extra burst of cheer in spring, tuck in bulbs like snowdrops, crocus, or miniature daffodils.
Why did my dahlia foliage go black?
Breda’s dahlias blackened during flowering. That’s the first frost at work – dahlias are tender perennials and collapse once the cold arrives. Cut back the blackened foliage and either lift the tubers to store indoors for winter or, in milder areas, mulch heavily and leave them in the ground. Either way, they should sprout again next year.
When should I prune?
Rebecca asks if pruning should be done now or in February. The answer depends on the plant, but as a general rule, late winter to early spring (February–March) is the best time for most pruning. You can remove dead or diseased wood now, but hold off major pruning until the plant is dormant. Remember: spring-flowering shrubs are the exception – prune them just after flowering.
Why don’t tulips come back each year?
Collette loves tulips but finds they vanish after the first season, even when she plants reliable Darwin types. Unfortunately, tulips don’t thrive in our damp soils. Even the most perennial varieties weaken after a year or two. Many gardeners treat tulips as annuals, planting fresh bulbs each autumn to guarantee a good display. If you want a longer-lasting bulb, try daffodils or alliums instead.
Should I cut back a mature camellia?
Ailish wants to tidy up a large camellia. The best time to prune is just after flowering in spring. Trim lightly to shape the plant and remove any weak or crossing stems, but avoid severe cutting as camellias don’t respond well to hard pruning. A good mulch and feed afterwards will encourage strong regrowth.
When should I divide agapanthus?
Anne wonders about dividing her agapanthus. The best time is in spring as new growth begins. Lift the clump carefully, split it with a sharp spade, and replant the divisions. Cutting the leaves back by about half will reduce stress while the roots establish again.
Final thoughts
September and October can feel like the garden is winding down, but it’s also a time to take stock, make notes, and prepare for the year ahead. Whether you’re protecting roses, planning tulip displays, or getting hydrangeas ready for another season, these small steps make a big difference to the health of your garden.
If you’d like tailored advice for your own garden, consider booking an Online Garden Consultation where I can guide you through planting plans, problem-solving, and design ideas from the comfort of your home.