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Deadhead, feed or leave it alone? Late-summer plant care explained
Seasonal Gardening
Deadhead, feed or leave it alone? Late-summer plant care explained
By mid-August, plenty of plants are starting to look a little tired. Some still have weeks of flowers left in them. Others are simply reaching the end of their natural season.
Deadhead, feed or leave it alone?
- Deadheading Deadhead plants that naturally repeat flower.
- Feeding Feed productive container plants that are still actively growing.
- Leaving alone Leave seedheads, hips, ornamental grasses and plants that have finished for the year.
- Checking first Check the plant group before doing anything enthusiastic with the secateurs.
Start by checking why the plant has slowed down
- Water shortage The plant may be short of water.
- Wet soil The plant may be sitting in wet soil.
- Root space The plant may be root-bound in a container.
- Natural season The plant may be naturally finishing its flowering season.
- Seed production The plant may be making seed instead of new flowers.
- Pests or disease The plant may be affected by pests or disease.
- Light levels The plant may be growing in too little light.
Which plants are worth deadheading?
Deadheading means removing faded flowers. On the right plant, this can redirect energy away from seed production and towards fresh buds.
It works best on plants that are already capable of repeat flowering.
Dahlias
Dahlias usually keep flowering well when faded blooms are removed regularly.
Follow the flower stem back to a pair of leaves or a healthy sideshoot and cut there. Do not remove only the petals and leave a bare stalk behind.
One useful check: unopened dahlia buds are usually rounded and firm. Spent flowerheads tend to become pointed, soft and rather less optimistic.
Summer bedding and tender container plants
Petunias, pelargoniums, argyranthemums and similar summer plants often respond well to regular deadheading.
With pelargoniums, remove the entire finished flower stalk rather than picking off individual petals. This keeps the plant tidier and reduces dead material around the crown.
These plants are also among the most likely to benefit from continued feeding because they are often growing in a limited volume of compost.
Penstemons
Remove finished penstemon flower stems back to a lower sideshoot or developing bud.
This may help extend the display, but avoid cutting the whole plant hard in late summer. Different penstemons vary in hardiness, and soft new growth can be vulnerable later in the year.
Repeat-flowering roses
Repeat-flowering roses can continue to produce blooms when faded flowers are removed.
Cut back to a healthy leaf or bud below the finished flower or cluster.
The important word here is repeat. Once-flowering roses will not produce another main flush simply because the old flowers were removed.
Leave some flowers in place where rose hips are wanted for autumn colour.
Buddlejas
Removing finished buddleja flower panicles can encourage further flowers on plants that are still actively growing.
Cultivars vary, so avoid treating every buddleja in exactly the same way, particularly where self-seeding is a concern.
When cutting back works better than deadheading
Some plants respond better to a trim than to removing flowers one by one.
Hardy geraniums and catmint can sometimes produce fresh foliage and a smaller second flush if tired growth is cut back after flowering.
By mid-August, that response depends on the weather, moisture and the condition of the plant. It is possible, not guaranteed.
Pulmonaria and oriental poppies may also produce fresher leaves after cutting back, but a meaningful second display of flowers is less likely. In that case, the job is mainly about tidying the plant.
Which plants may still need feeding?
Late-summer feeding is most useful for plants that are growing in containers, still actively flowering, watered regularly, healthy enough to respond, and expected to continue performing into early autumn.
Good candidates include hanging baskets, window boxes, flowering annuals, pelargoniums and dahlias in pots.
Use a feed intended for the plant and follow the current label. Products vary, so do not guess the dilution or frequency.
Established shrubs and perennials growing well in open ground often do not need routine liquid feeding. Adding fertiliser will not persuade a plant to restart if its flowering season has naturally ended.
It is also worth checking the real cause of poor growth before feeding. Yellow leaves, flower drop and weak growth can result from too much water, too little water, poor drainage, restricted roots or low light.
Fertiliser is useful. It is not an all-purpose apology.
Plants that are often better left alone
Not every faded flower needs removing. In some cases, the seedheads or spent blooms are part of the plant’s autumn and winter value.
Mophead hydrangeas
Leave faded mophead hydrangea flowers in place over winter.
The old flowerheads can offer some protection to the buds below. They are normally removed in spring, once the worst of the cold weather has passed.
Do not apply this instruction to every hydrangea. Mophead, lacecap, panicle, smooth and climbing hydrangeas have different pruning needs.
Lacecap hydrangeas
Lacecap hydrangeas may be deadheaded more carefully after flowering, usually by cutting back to a suitable pair of leaves below the flowerhead.
That said, there is no need to remove the heads if they still look attractive and the plant is healthy.
Ornamental grasses
Leave ornamental grass flowerheads in place.
They add movement and structure through autumn and winter, and there is little benefit in cutting them down in August.
Roses grown for hips
Leave some spent rose flowers where hips are part of the autumn display.
Deadheading every bloom removes the chance for those hips to develop.
Sunflowers and decorative seedheads
Sunflowers, echinaceas, eryngiums, rudbeckias, alliums, honesty and similar plants can all develop attractive seedheads.
Some offer food for birds. Others provide structure or simply look good through autumn and winter.
Those are different benefits, so it is better to judge the exact plant rather than calling every seedhead wildlife-friendly.
Plants that are still flowering
Do not cut down a whole plant simply because part of it looks untidy.
Late-flowering plants such as heleniums and Michaelmas daisies may still be producing useful flowers well into autumn. Remove individual faded blooms where practical, but leave actively flowering stems in place.
Plants that do not need constant attention
Some plants produce too many small flowers to make deadheading worthwhile. Others are difficult to reach or are being left to self-seed.
Asters, trailing campanulas, some spiraeas, deutzias and thalictrums may not need individual faded flowers removed.
Gardening does not require a daily inspection of every brown petal. The plants will cope with a little administrative delay.
A simple late-summer checklist
- Is the plant still actively growing? Look for fresh buds, healthy leaves and new sideshoots. If growth has stopped naturally, more feeding or cutting may achieve very little.
- Does it normally repeat flower? If it does, deadheading may help. If it flowers once, removing the old blooms may only make it tidier.
- Is it growing in a pot or basket? Container plants are more likely to need regular watering and feeding because their root space and nutrient supply are limited.
- Does the seedhead have a purpose? Leave it where you want hips, seed, autumn structure or winter interest.
- Is the plant healthy? Do not feed automatically. Check moisture, drainage, root space, pests and disease first.
The late-summer rule worth remembering
Deadhead repeat flowerers. Feed healthy container plants that are still performing. Leave seedheads and naturally finished plants alone.
And when you are not sure, identify the plant before cutting it back. “Hydrangea” and “rose” are broad groups, not complete care instructions.
