Self-sown ornamental seedlings

Many annual and perennial ornamental and bedding plants have the very obliging habit of self-seeding if their seed heads are left in place after flowering. This means they simply drop their seeds onto the soil where they’re growing. This results in lots of – often too many – new plants growing the following year when the seeds germinate.

However, as numerous seedlings will grow very thickly in a limited amount of space, the developing seedlings often don’t grow into healthy plants. And, if they’re all left where they are, they can be regarded as “weeds”.

And as “One year’s seeding means seven years weeding” you may have many years of clearing them away, or weeding, ahead of you!

• Beds
• Borders
• Lawns
• Gravel paths
• Between paving slabs
• Waste or uncultivated ground

There is a huge range of annual and perennial ornamental plants that self-seed. When the seeds germinate, you may think the resulting seedlings are weed species, as you may not be able to tell the difference between them and weeds. You need to know what the ornamental plant seedlings look like to differentiate between them.

You may not want to control them, as these are a great source of free plants for you to grow on! But as they tend to grow in congested clumps and may not develop into healthy plants as a result, you should either thin them out, so each plant has enough room to grow in, or even carefully lift them and pot them on. Then remove all the others you don’t need or want.

Just be aware that if the seedlings arise from F1 hybrids, they will not come true to type/true to the parent plant the seeds came from, and will have differing characteristics of flower colour, flower size etc.

Regularly hoeing the emerging seedlings or young plants as soon as you see them is the quickest and easiest method of control. The aim of hoeing is to sever the plant stems at or just below ground level, cutting the top growth from its roots. A sharp hoe blade will make this even quicker and easier, so always sharpen the hoe blade before use. Hoeing on a warm and/or windy day will mean the plants quickly dehydrate and die.

Digging out the plants, particularly when they are more established, is more time consuming and more difficult – especially where they’re growing among wanted plants.

In lawns, regular mowing and feeding throughout the year should prevent self-sown seedlings from becoming established in the first place, or control them if they do.

There are a number of weed control options available. In addition to traditional weedkillers there are now also a range of more natural alternatives.

Any weedkiller can be used to control and kill self-sown seedlings. Those marketed as “fast acting” are contact weedkillers – killing or damaging the plant tissue they are sprayed onto or make contact with. These tend to be based on “naturally-occurring” active ingredients, such as acetic acid and natural fatty acids.

Systemic weedkillers that also kill the roots, can also be used.

To ensure weedkillers work more effectively:

• Spray the leaves when the plants are growing actively; this is mainly from March/April to September/October. Contact weedkillers will have some controlling effect if used during the colder weather in winter.
• Use a fine spray to thoroughly coat the leaves in small droplets.
• During the summer, spray in the evening to prevent the spray evaporating and to give maximum time for the spray to work. In spring or if overnight dew is forecast, spray earlier in the day to allow the spray to dry before dew falls.

Most weedkillers (except lawn weedkillers) are total weedkillers – that is they will damage or kill any plants whose leaves they are sprayed onto. Make sure you keep the spray off wanted plants – including lawns – and, if necessary protect wanted plants by covering with polythene or similar when spraying.

Use weedkillers safely. Always read the label and product information before use.

If you don’t want any self-sown seedlings, don’t allow plants to set seed. Deadheading once the flowers fade – making sure to remove the developing seed head behind the flower – or cutting down flower stems after flowering, will ensure no seeds are set. This will also allow plants that have the capacity to repeat flower that year to produce further flowers.

If you want to produce new plants from seed, either harvest the seed before it drops to the ground, or thin out the seed heads to one or two per plant to reduce the myriad of self-sown seedlings that are produced.

• Spade
• Fork
• Hand fork
• Weeding tools
• Hoe
• Weedkillers