Taking care of dahlias: the trick with deadheading

taking care of dahlias purple dahlia

To my mind, one of the greatest strengths of dahlias, is that they can go on flowering from mid-summer right until the first frosts.

Depending on where you live, that could mean that you can have dahlias in bloom for three, four or even five months.

However, the most important word in that first sentence was can.

Once you know how to grow dahlias, they can flower for extended periods but only if you, the gardener, help them do so.

Taking care of dahlias involves the usual necessities of feeding, watering and mulching. But to get prolonged flowing, you need to dead head.

And it can be a little bit harder to dead head dahlias than it is for most flowers, unless you are aware of one important fact – how to identify the spent flower head.

(I have to say, I can never think of dead heading, without thinking of the Grateful Dead. But maybe that’s just me.)





The two step tip for dead heading dahlias

In case you don’t know, dead heading is simply a matter of removing spent flower heads.

This prompts the plant to produce more flowers, because removing the spent flowers deprives the plant of the potential seeds that evolution is driving it to produce.

Step 1 – Identify the spent flower

This is what makes dead heading dahlias a little bit tricky.

The problem is that once all the petals have fallen from a spent dahlia, the hard green part at the base of the flower (the calyx) closes over and what is left looks very much like like a bud.

So unless you know how to tell the difference between the buds and the remains of the spent flowers, you can end up removing the very buds that you are trying to induce into flower.

Fortunately, it is pretty easy to tell which is which when you know how. So here’s the trick:

The buds are rounded and the dead heads are cone shaped.

Take a look at the picture below.

This is a bud.

It is rounded, a kind of flattened sphere of compressed petals, with the calyx (the hard green outer ring of sepals) fanned out below the bud.

taking care of dahlias bud

Rounded dahlia bud - do not remove

In contrast, what you see below is the spent flower.

Notice how the overall shape is pointed rather than flattened, a cone instead of a sphere. In addition the sepals of the calyx have folded up to enclose and protect the reproductive parts of the plant.

These are what you need to remove.

taking care of dahlias dead head

Cone shaped spent dahlia flower: remove these

Step 2 – Cut right back

This is the easy part.

When you remove the dahlia’s dead head, don’t just cut it off below the flower. If you do, you’ll leave a flowerless stem that will just look ugly.

Instead, cut back, with sharp secateurs, to just above the point where the flower stem joins a main stem.

As you do so, you’ll probably notice a couple of tiny buds nestling there. With the removal of the spent flowers, those will sparked into life and they will bloom in a week or two.

If you are attentive in taking care of your dahlias and keep up your dead heading regime all summer, you’ll have blooms until the plant is knocked over by the first frost.





What you might need

If you’re just deadheading your dahlias, you can just as easily use kitchen scissors. But if you’re anything like me, then you’ll be scanning the garden for anything that needs a prune or a bit of cutting back while you’re there.

I pretty much never step into the garden without my classic Felco Classic number 2 secateurs. These are the best secateurs or pruners I’ve ever found – and, believe me, I’ve tried plenty.

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Buy dahlias

For a great selection of dahlias, check out what is on offer at DirectGardening.com – you’ll find quality plants at great prices.


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These unique dahlias are shipped as large, number one size clumps. This Powder Puff Dahlia is almost the size of dinner plate dahlias. Produces rose petals with a creamy white center and a deep rose heart. Grows 40-44" tall.






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More on taking care of dahlias

Read more on how to grow dahlias, with full cultivation notes here.

taking care of dahlias


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Comments

  1. Sheila Fox says:

    Thanks. Glad to get that info on dead heading dahlias. Looking forward to more blooms.

  2. Do they come up every year? Can’t remember the term names.

  3. Oh! Are they annuals or perrenials?

  4. Lesley Miller says:

    Question; do Dahlia’s grow & bloom best in clay pots? Plastic? I have gophers and don’t trust them in the ground,….
    Thanks for getting back to me /us :)

    Lesley
    Santa Cruz, CA

    • Hi Lesley
      On the whole they do better in the ground and are easier to look after (not so much watering). But there’s no reason why they can’t grown in pots. I’ve always grown dahlias in the ground but I’m actually growing a dahlia in a pot for the first time at the moment, so I’ll keep you posted on how it goes.

      You can use clay or plastic pots, although I’d usually choose a clay pot because sometimes plastic pots can get really hot and damage the roots of the plants. This is less of an issue if it’s a large plastic pot.

      When growing dahlias in pots, you need to make sure they don’t dry out and keep them well fed – see this post on growing dahlias.

      Hope this helps.

  5. Chuck Lasher says:

    I have had great luck storing my dahlias in Pro-Mix. It is light, fluffy and dry. After lifting, cleaning and drying, I divide each clump, which is the hard part, then put each division in a ziploc bag , covered with Pro-Mix then zipped shut. These are then placed in the coolest corner of the basement. Nearly 100% success every year.

    • Sounds like you’ve got it very well under control Chuck.

      I agree dividing dahlia tubers is a bit hard. I always end up with a few loose ones with mo growing point. That’s why I always wait till there’s a sizable clump.

      Thanks for your tip.

    • Your dahlias are abutoslely amazing. Are they perennials where you live? We have to lift the bulbs in the fall, which is why I’ve never tried to grow any.

  6. How do you prepare the plants for winter? They are brown and look dead. Do you cut the plant off at the ground?

    Thanks,

  7. I liver in central Florida, will the blooms continue all year or will plant die back in the cooler weather?

    • Hi Lynn
      I think they’ll still go through the perennial plant cycle of growth and die back, but you’ll probably get a longer flower season. You could try some heat tolerant varieties, e.g. Bloodstone,Thomas Edison, Juanita, Prince Noir, Jersey’s Beauty, Bishop of Llandaff, Deuil du Roi Albert, Surprise, Lavengro, Princess de Suede or Winsome. Also make sure they are well watered but that the soil is free draining. They won’t cope with being waterlogged.

  8. if I leave the tubers in the ground over winter do I need to cut them to ground level first

    • Hi Harry
      Yes, once they’ve been hit by the first frosts or bad autumn weather, you should cut them down to ground level and then apply a good layer of mulch. They should be fine if your temperatures don’t get much below -5 on a regular basis, although the tubers could rot if you get lots of rain and the soil is sodden for extended periods.

  9. Kristin says:

    Thank you so much for this info! I wasn’t sure how to deadhead my dahlias – at the base of the flower or the stem, but you certainly cleared that up for me! I am in NYC and have mine in pots and window boxes, so it is easy for me to see the spent blooms. And no, you’re not the only one that thinks of the #GratefulDead when using the term “deadheading!” You have a new fan in me! LOL!

    • Hi Kristin Thanks for your comment. I’m glad the info has helped you. I’d love to see your display of Dahlias. I think I’ll have to try to work out a way for readers to upload pics of their gardens and plants.

      • I’ve now included a page where readers can upload their own garden and plant pics, tips and gardening stories. Click here and follow the instructions.

  10. Gabriela says:

    Hi guys,
    I’m growing dahlias in a large plastic pot for the first time. Until two weeks ago, i had beautiful red flowers with bright yellow centers, and multiple flourishing buds. However, they suddenly started to die out and the new ones are now small pink-yellow flowers and few buds. The soil hasn’t gotten too dry (I used micracle grow potting mix). The weather in the north east has been ok – some night are still chilly but not below freezing, certain days humid but not too bad. I’ve frequently moved them inside and outisde the house to protect them from heavy rain.
    What could be potential causes? Is there a recommended water regiment i should be following? What about light exposure? What else could I do that might help me get them back to big red beautiful dahlias? Will they come back?
    Thanks a bunch!

    • Hi Gabriela. Sounds like a tricky problem. One cause could be that the soil is too wet. Dahlias can’t stand being waterlogged, so I’d suggest you make sure that there is good drainage through your pot. Plastic pots can hold water much more than clay pots, so I’d check that the soil is not waterlogged around the roots of the plant, even if the surface seems dry.

      Another thing that dahlias need is a good supply of sunlight, so I’d try to keep them outside, in full sun , as much as possible.

      If they’re in miracle-gro potting mix, it doesn’t sound like they need feeding. Sometimes over-feeding will kill plants, so unless they’ve been in the mix for a long time, so that all the nutrients in the mix have been depleted , I’d hold off on the feed.

      Hope this helps. Let us know how it goes.

  11. Sheila Marler says:

    Do you let the blossoms completely die , before deadheading. Or do you cut them off, when they start to turn brown. Thanks. This is my first year , I am growing them in containers. Thank you. For all of the information.

    • Hi Sheila
      It’s up to you really. I do it when I notice a bloom is fading. I think that technically, as soon as the spent flower is removed, then the immature blooms get a signal in the form of a hormone to begin the flowering process. But, if you’ve got a plant with plenty of blooms, then some are likely to get to the cone-shaped, spent flower stage before you catch them. The best advice is just to make sure you deadhead on a regular basis so that you’ve always got some new blooms coming through.

  12. I am growing dalias in South Carolina for the 1st time. They are in plastic pots in almost full sun. However, the petals are turning brown before the bloom has fully opened. What do you think the problem is?

    • Hi Gayle
      Like all things in gardening, Dahlias like it just right. They need sun and they need to not be waterlogged, as I’ve said above. But – if the sun is very intense, especially at midday, the petals and buds can burn. Also, when the weather is warm, make sure they get enough water – not so that the roots are drowning for any prolonged period, but enough to ensure the soil doesn’t dry out for any length of time. This can be a problem with any plants in pots. Also check out your feeding regime. I’ve read, though I haven’t verified this yet, that they should not have fertilisers high in phosphorous. So make sure the middle number in the NPK number on the fertiliser packet is not too high.

      Also are there any problems with the leaves? Are they yellowing for example? Is there yellowing around the veins? These kids of symptoms can signifiy nutrient deficiencies or imbalances.

  13. Shirley says:

    This is my first year growing Dahlias, and I am having a problem with something eating the flowers, little bits at a time!!!!! What can I spray on these gorgeous flowers to protect them??? Also, I find that earwigs like to tuck in the flowers as soon as they start to fade…….that’s easy enough to handle, as I deadhead very quickly, but I would like to ask…”Do Dahlias attract earwigs or do I just have an overabundance of earwigs, and not enough good hidey spots for them?????

    • Hi Shirley
      Earwigs are known to be attracted to dahlias, so there is a good chance it’s the earwigs that are nibbling your flowers. I’m reluctant to recommend spraying because then you’ll also kill the good bugs like ladybirds (ladybugs) and hoverfly larvae that will protect your plants from other pests like aphids.

      One old gardeners’ trick to deal with earwigs involves placing a small upturned flowerpot stuffed with straw or tissue paper on stakes in amongst your plants. This provides the kind of daytime hiding place that earwigs like. You can empty out the pot each afternoon and destroy the earwigs that collect there, or just empty the contents into a plastic bag, tie up the end and put it in your bin. This should help keep the earwig population under control.

      It’s hard to recommend a product if you do want to use an insecticide as what is available will depend on where you live. For example, in Europe now very many insecticides have been banned. In any case, you might find it is best to use a granular product rather than a spray as this can be more targeted.

      Hope this helps.

  14. Shirley says:

    This is not another question…….I just forgot to click the “Sign up to our newsletter” box!!!!!

  15. Barbara o'keeffe says:

    how often should i water and feed my dahiias? this is my fist time gardening and im loving it…

    • Hi Barbara
      I’m glad you’re loving your gardening experience. There are some dahlia growing tips here. Keep the soil reasonably moist, but not waterlogged. Feed them with a nitrogen-rich fertiliser in early summer and a potassium-rich fertiliser once they are flowering. Once a month should probably be enough.

  16. i have started to dig up my plants and have noticed after a week they seem to be getting soft. I have them laying on paper bag in basement. I have planted these for 3 or 4 years and did not realize they were able to be saved. I would just notice that they were soft and mushy and I would throw them away. Someone told me peri all and I thought they were annuals. I am so excited because I have picked well over 300 flowers this year off of my dahlias. I sure hope I can save them from year to year. Thank you for your help…I really enjoy the tips on your site.
    Sandy

    • Hi Sandy
      Glad you’re enjoying the site.

      Make sure you lay the tubers upside down to dry out. They have hollow stems and water may well be lying in the bottom of the the stems that you cut back.
      This water needs to be drained out or it can make the tubers rot.

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