Why do we deadhead old flowers?
‘Deadheading’ refers to the removal of old flower heads from plants. This is generally done to encourage certain plants to reflower, although it can also be done for decorative reasons when old fading or dead flowers look unsightly or are spilling petals around. It can also be carried out to stop certain plants, like Libertia and foxgloves seeding around the garden to a point where they may become invasive. Deadheading will also divert all the plants energies into strong growth rather than seed production.
We associate deadheading mainly with annuals, summer bedding, herbaceous perennials, bulbs and roses. Although you can deadhead any plant and it won’t actually do any harm. The process of deadheading won’t necessarily make your plants re-bloom, it has to be a plant that is responsive to the treatment.
Most shrubs don’t require deadheading although it is beneficial to Rhododendrons and Camellias for energy directing reasons. Shrubs like Ceanothus, Cistus and Choisyas are often clipped after flowering anyway to help them keep their compact shape which will infact deadhead them at the same time. Obviously by removing the old flowers of shrubs, or any plant come to that, that produce berries or decorative seed heads will needless to say result in no berries or decorative seed heads. Plants like Pyracantha, Skimmia, Euonymus europaeus and Callicarpa as examples.
Earlier in the year your spring bulbs should have been deadheaded, removing the old flowers just under the joint with the stalk which is left as it will photosynthesize as will the leaves providing energy to the bulb for next years flowers.
Most earlier, before June, flowered herbaceous plants don’t repeat bloom well if at all but the removal of the old flower stems and even cutting their foliage back hard will certainly leave the plant looking tidier and more healthy for the rest of the year. Helleborus, Pulmonaria, Brunnera, lupins, delphiniums and some Geraniums are included amongst others. The hard cutting back of these plants is playfully known by gardeners as the ‘Chelsea chop’ as it is carried out at the same time as the famous flower show.
Late flowering herbaceous plants like Penstemon, Scabiosa, Geum, Asters and Rudbeckia can all be deadheaded to encouarge flower well into the autumn and even, in favourable conditions, early winter. With a plant like Agapanthus, which won’t repeat flower, I leave the seed heads as they are quite attractive and from my experience don’t seem to hinder next years flowering at all.
Annuals and bedding plants can be deadheaded on a daily basis if you have the time but should be checked at least once a week if you want perpetual flowering. Small flowered plants like lobelia and alysum don’t need to be looked at at all. Bedding Fuchsias often don’t set seed, the flowers just fall off, but keep an eye. Bedding geraniums need regular deadheading.
With roses that repeat flower it is essental to regularly deadhead. You can do this by taking off individual flowers as they fade or if there are large clusters take the stem off that is carrying them just below the the flower cluster. If you want to keep a bush small and tighter you can cut down the stem to half way and the rose will re bloom but it will take longer for that to happen.
Deadheading can be by hand using the thumb and fingers to pinch off the dead flower heads or by secateurs. In general stay close to the bottom of the flower you want to remove but as mentioned already with the roses if you need to contain the size of the plant heavier removal can be done. Don’t tug and pull to remove as this may destabilize the plants root system.