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Over-seeding Fact and Fiction

Another very popular subject on this site is over-seeding of greens in Autumn.

Over-seeding is commonly carried out as part of the autumn bowling green maintenance and renovation program and is very often a disappointment.

You would expect this work to quickly fill in the bare patches and spaces in the sward left by  disease, localised dry patch and a host of other green problems, but this is very often not the case…why?

The answer to most disappointing results from over-seeding is “competition”. Competition from the mature, indigenous grasses whether fine or weed grasses like annual meadow grass usually reduces the success or survival rate from over-seeding to a very small percentage.

This quite often comes as a surprise to greenkeepers who have observed a very good “take” shortly after seeding (7-14 days). At this early stage it is not uncommon to see vigorous lines of dense new seedlings bursting forth from the green. This however, is usually a false reading.

At this very early stage the seedlings are still living off the food reserves in the seed itself, but they very quickly have to turn to what they can find in the soil to survive and thrive. This is when the major problem kicks in, as they are not only competing with each other for light, air and nutrition but also with a mature sward of indigenous grasses and other plants. Then there are the other problems of disease; damping off, a fungal disease that attacks seedling turf is a common problem where seed is sown densely and the onset of winter.

These factors combined can quickly turn what looked like a 99% germination rate into a 2 or 3% survival rate in the long term. So what can be done to maximise the success we achieve with over-seeding:

  1. Get the seed in as early as possible in the autumn to give it access to sufficient light, warmth and nutrition.
  2. If you have thatch issue (in excess of 5mm thick) don’t bother; instead concentrate on repairing bare areas with plugs of turf from the corners or if you have to use seed on bare spots, renovate these thoroughly by hand and produce a good seedbed for the new seed.
  3. Put the indigenous sward under a bit of stress prior to over-seeding by scarifying it severely to weaken it just enough to buy the new seedlings some time.
  4. Always over-seed with a proper over seeding machine which gets the seed into the soil and applies it accurately into the bargain.
  5. Make sure there is sufficient moisture to get the plants going quickly.
  6. New seedlings need a bit of Phosphorous to get their roots going quickly so make sure this is applied but not too heavily.
  7. Don’t be over ambitious; large bare areas are unlikely to recover fully by simply over-seeding them.
  8. Make sure you have selected a quality seed mix and that it has a certificate and germination and purity statistics attached.

Over-seeding isn’t the fix all that many people expect it to be, but go into it with your eyes open and it can be a very useful tool in the greenkeeper’s armoury.

6 comments

  1. John Wilkinson says:

    Hi John, Would it not be better to overseed late winter/early spring? The grass seed does seem to take better early spring time. Also most of the disease would be eradicated by then. Regards John

    • John Quinn says:

      Hi John

      Good to hear from you.

      Overseeding into an established turf is difficult at the best of times with long term survival being very low in many cases.

      There are many factors to consider before even bothering to overseed. The green has to be in fairly fine fettle as far as thatch control and soil health is concerned, so overseeding into a sickly or recovering green is usually futile.

      If there is an optimum time it is early autumn when there is some warmth left in the soil and the major work of the autumn renovation program is over.

      This gives the new seedlings the best chance of establishing for several reasons:

      1. The native grass has been stressed and thinned by the autumn renovation work.
      2. Space has been created (by the work above) to allow the new seedlings to set roots right after the seed food reserve has been exhausted; this is a critical time.
      3. The new seedlings have a few months to establish before being subjected to intensive maintenance and close mowing.
      4. The seedlings are established and rooted by the time they have to compete fully with the native grass during the spring growth surge; newly planted seeds trying to establish roots at this time would find it very difficult to get a foothold.

      After seeding it is usually encouraging to see what appears to be a near 100% success rate, but this is due to the new seedlings being nourished completely by the seed reserve. As soon as this seed reserve is exhausted the tiny plant has to fend for itself within a mature, established turf. Long term success of 2% or less is not uncommon, hence the need to stack the odds in favour of the new seedlings as much as possible.

      Hope this helps

      Regards

      John

      • John Wilkinson says:

        Hi John, Thanks for your reply. I’ll bear it in mind about the seeding times. 2% success rate does not sound good, and makes you wonder if it’s worth the outlay to have it done in the 1st place. Far better to spend the hard earned money aeration.

        • John Quinn says:

          Thanks John

          The success rate can be increased dramatically if the measures I mentioned are addressed first.
          However, the 2% figure wouldn’t seem unusual to an Ecologist (overseeding a bowling green is like introducing orphan lambs to a forest populated by wolves) and it’s the ecology of bowling greens that we need to understand more than anything if we want to be successful at producing performance bowling greens.
          I’m in the midst of writing a series of articles on this subject. The first 4 are on the site already.

          Regards

          John

  2. Eric Barklem says:

    Hi John.
    At the beginning of September we scarified a new bowling green and over seeded by using the correct machine for this task but in the North West it has rained very hard over the last three weeks and the ground is soggy, moss has appeared in places can moss killer be applied with new seed or should we leave it until early next year in March?

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