The summer play season has come to an end and for the enthusiast, keeping the lawn in good shape is a priority whilst there is still some warmth in the soil. September is an ideal month for re-seeding the lawn surface so that worn and bare areas can be rejuvenated.
Some gardeners think that new grass seed can be sprinkled on a bare patch, covered with a few millimetres of compost and left to germinate.
Sadly, all too often, this method ends in failure because the new seed, - if not eaten by the birds - when it starts to root, cannot penetrate through the compacted crust of the surface levels.
For good grass germination it is advisable to take out a 10 - 20mm core of compacted soil to a depth of 50-75mm. By removing this core, you have effectively created a small pot that can then be filled with a root zone dressing where new seed can germinate into and remain protected from predators, weather and foot traffic.
Recommended action.
Cut your grass (preferably the day before) to height that will not interfere with the process. If the grass is too long, it will not be easy to distribute your turf dressing.
Hollow coring (or hollow tining) is best carried out as part of a regular maintenance regime. If you plan to scarify then this ideally needs to be done two to three weeks before so that the surface is still intact otherwise creating a solid core may be difficult.
You may prefer to defer the scarifying or just use the scarifier to groom the surface to remove lateral growth and thatch with no real penetration into the soil structure.
Aerating is best carried out in the afternoon when the grass and surface of the lawn is dry. This prevents your feet from making a sticky mess and helps prevent the hollow tines from blocking up.
There are two or three acceptable routes you can take now. You can remove the cores, clean them from the surface and then broadcast seed over the surface so that a proportion of the seed is dribbled into the holes. Watering the lawn after completion will ensure that seed finds its way to the bottom of the hole and with a little soil that is washed on top of the seed provides a free and easy space for the roots to germinate.
The draw back with this method is you do not replenish any of the existing root zone soil structure with new medium and the grass seed is forced to germinate deeper than might be required. If the holes stay open and there is still good warmth in the soil you may find that the grass thrives and reaches the light in time for partial dormancy in through the winter.
If the seed fails to germinate and reach the lawn surface then the new shoot or seed will rot in the hole and the process will be spoiled.
The second and probably more favourable method is to aerate the lawn so that the core is ejected onto the lawn surface and then collected and removed.
Broadcast fresh grass seed depending on your requirements and then broadcast fresh soil/compost/sand dressing mixture (again the dressing you choose will depend on what your lawn is going to be used for).
Now, using a lute (basically a wooden or aluminium straight edge about 600 - 750mm wide attached to a handle that is drawn back and forth. The lute will push and pull your soil and act as a grader across high spots. Continue to distribute the soil until it has an even covering over the surface. I like to see the existing grass showing through.
Try to imagine that you are levelling pits and scrapes but also, and essentially, you are encouraging the grass seed and dressing to fall into the open tine holes.
As the seed and soil dressing falls into the holes in a random fashion, the seed will be contained within the soil at varying depths so your success rate for viable germination is favourable.
The third method involves broadcasting your grass seed and proceeding with your tining. As the cores fall onto the surface of the lawn, leave them there and be careful not to compress them with your feet or machinery in any way. Let the cores dry in the breeze and the sun.
Now start knocking the cores about with a brush or lute so that they start to break up. If you have an scarifier with an old set of worn tines then you can use this - be sure not to set the blades so that they penetrate the soil surface, you just want to break up the cores.
Keep distributing the cores until you are happy that the old soil, which is now de compacted and invigorated, has fallen into the holes.
Now you can either set the sprinkler for a period of time to moisten the soil or leave for mother nature to intervene. Germination of the seed can take 7-14 days depending on how late you carry out the process.
Be careful about leaves building up over the surface of the lawn because you may find that the seed will not germinate or quickly die because of the lack of light.
Using a backpack or hand blower to remove the leaves is perfect because you do not have to aggressively make contact with the soil as you might do with a spring rake.
The image is of a foot operated hollow core aerator and is not designed for larger lawns.
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