The Lawn Overseeding Guide

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The Lawn Overseeding Guide


 Once the actual overseeding of your lawn is complete, it is important to understand the many factors that will influence the success of its establishment. The following information covers a majority of the most frequently asked questions regarding overseeding.  As always, if you have any questions or are unclear about anything at all, please give us a call at (717) 299-2112 or toll free at 1-888-246-5433, and we will be glad to help you every way that we can!  You may also e-mail your questions to and we will respond promptly.




The most important step in establishing your overseeded lawn is to water, water, water.  It has been proven repeatedly that well-watered seed will germinate more quickly, establish more densely, and crowd out potential weeds more effectively than seed that receives little or no water.  Despite this, we do understand that there may be situations that make it difficult to water as much as we recommend.  For instance, there may be problems with time constraints, low well-water levels, drought restrictions, reaching distant areas from a water source, vacation timing, or one of many other factors.  If you cannot water, the lawn is likely to establish adequately from morning dew and rainfall (if seeded in the fall), but it may take longer, and increased weed content and reduced turf density may occur.  We strongly encourage you to follow the Watering Instructions For Newly Seeded Lawns handout as much as possible. In the case of a severe drought there may be certain watering restrictions mandated by the city.  If this should occur, please contact our office and we will provide you with a current listing of approved watering situations and times.  Usually there are provisions that allow for the watering of newly installed plants and lawns at predetermined time intervals.





Although heavy rains can cause significant damage to newly seeded lawns, it is much less likely to occur in an overseeding situation.  There are two main reasons for this: firstly, the overseeding machine slices the ground and drops the largest portion of the seed into the groove in the soil.  This prevents the seed from being caught in the main flow of water.  Secondly, in most overseeding situations there are least some existing grasses (or weeds) in the lawn.  The existing plants will anchor the soil from washing and reduce the flow rate of water through the lawn (although in a torrential rain it may not seem like it!).  Both of these factors greatly minimize the likelihood of severe erosion or seed washouts taking place.  Even if you see a pile of seed sitting in a puddle on the driveway after a rain, it would represent a very small percentage of the total seed used in the yard.  Unless you have requested a significantly lower than normal seeding rate, there should still be plenty of seed to take hold and thicken in the lawn.  Of course, if you have any doubts or questions, please let us know and we will be glad to help you every way that we can.





It is important to provide the lawn with adequate moisture throughout its first full year of establishment.  Generally, in our area watering should be performed April through December whenever the soil looks dry.  It is important to remember that soil moisture can evaporate just as quickly in the windy/arid conditions of spring and fall as it can during the hot/dry conditions of summer.  Both sets of conditions can quickly lead to a dry lawn, which could be damaged if not watered.  Once the lawn makes it through its first year of establishment, its susceptibility to drought and heat stress is reduced, but not eliminated, and watering during extended dry periods is always recommended.





The length of time is takes for seed to germinate depends on the varieties of seed used, the soil conditions present, the amount of thatch in the lawn, the current climatic conditions, the seed’s exposure to sun, and the amount of water it receives.  Under “average” conditions in the fall, most overseeding should begin to germinate within 14 to 21 days.  Please remember that it is normal for some spots to germinate more quickly and others to germinate more slowly.  If the seeding is done in the spring, it should be expected that the germination time would be about a week longer than in the fall (under the same conditions).  The complete germination process will occur over several months.  The germination will be slower if the seed is not watered faithfully, if it is a heavily shaded area, if the soil temperatures are cool, if the seedbed is disturbed, or if the soil is severely compacted.  


After the lawn has germinated, the length of time it takes to complete its establishment is much less variable.  Generally, it takes one full year for grasses to reach their maturity.  During the first year the grasses are continually thickening and developing to a point of peak hardiness.  Tall Fescues in particular reach their optimal level of hardiness in their third full year after seeding.





Most likely nothing is wrong at all!  Because of the many factors that affect seed germination, it is normal for some areas of the lawn to germinate and establish more quickly than other areas, even if you are watering them all equally.  During the first few months it is very common to find thinner looking spots in sections of the lawn.  Given enough time these spots will thicken and mature along with the rest of the lawn.  If, after a few months, there are distinct bare patches, some spot touch-up seeding may be necessary to ensure the lawn thickens properly.  If there are noticeable ruts or washout areas they should be taken care of as soon as possible to ensure they do not worsen.  Please note that any sections of the lawn that have heavy thatch will likely take longer to germinate.  A heavy thatch layer reduces the seed to soil contact, which slows the germination process.  If you know that some areas have a heavier thatch layer, those areas should be watered more heavily to help them along.




Yes!  Anything that disturbs the seedbed is a problem.  When the seed becomes dislodged from its spot in the soil it delays its germination, or if it has already germinated, its fragile root system will tear and the plant will die.

If you see mounds of soil with pinky-sized holes in the middle or small trails throughout the soil, like someone ran their finger through the icing on a cake, it is usually indicative of white grub activity.  The most common pest of newly seeded lawns is the Green June Beetle grub. If you are unsure if there is grub activity, try inspecting the lawn at night with a flashlight (10 PM is often a good time).  If there is activity you will likely see small, thick grubs inching around on top of the soil or walks.  Green June Beetles are easily identified by the fact that they crawl on their backs.  If you pick one up and place it on pavement it will flip over on its back and begin to crawl away like an inchworm.  These grubs are often present in a balanced soil ecosystem and rarely cause significant damage to growing turf.  However, when a lawn is re-seeded the tunneling and crawling activity of the grubs dislodges the seed and can cause significant damage to the reseeding work if it is not treated immediately.  In any given year as many as 1 out of 5 newly seeded lawns may show some symptoms of Green June Beetle activity, so please keep a watchful eye on the new grass!


If you notice any activity please contact us immediately so that we can control the situation before significant damage takes place (we will always provide an estimate before making any application).  In this instance it will be necessary to apply a synthetic material to control the grubs.  Natural controls that may be effective against the grubs take too long to be completely effective and damage to the seeding work could result.  If you are uncertain about whether you are seeing any activity it is best that you contact Organic Approach at your earliest convenience so that we may assess the situation.





The many clumps of grass you may see on top of the lawn are clumps of thatch and/or weak grass plants that were dislodged as the overseeder made its slits into the soil.  Although it may appear that there is an enormous amount of material on top of the lawn, the material is generally very light (it is just fluffed up) and it should not smother any grass.  We recommend that you leave this material on top of the lawn as it shades the seed and soil from the sunlight and keeps moisture on the seed longer.  It is similar to putting straw on a new lawn.  The clumps will decompose naturally after a few weeks and they will NOT add to or promote any type of thatch layer.  If you see a few “heavy” clumps of grass that just seem too thick to leave on the lawn, please break them up by hand and scatter them on top of the grass.  If you wish to chop up the clumps, you can mow the lawn one notch HIGHER than you did when you “scalped” the lawn down for our overseeding work.  Do not catch the clumps!  Not only will it take you forever to bag that much material, it will reduce the mulching benefits it provides for the new seed.  Mulching mowers and side discharge mowers will work fine.  By mowing one notch higher than the last mowing you will only be chopping the main clumps of grass and will not disturb the seed at the soil level.





The lawn may be mowed whenever the new or original grasses reach about 3 ½ inches.  Since in most cases the existing lawn has been cut lower than normal for our overseeding, you may not have to mow the seeded areas again for up to two weeks.  When you do mow, the mower should be set back up to the height at which you have been mowing the lawn all year.  There is no need to bag the clippings, although you may do so if the lawn has grown too high and the clippings would smother the seedlings.  Most likely, the lawn will not establish at a uniform height, so the lawn should be mowed when approximately half of it has reached the 3 ½-inch height.  The last mowing of the year and the first mowing of the next season should be at a height of 2½ inches.  Avoid mowing the lawn when it is wet as it can be easily damaged.  Try to avoid mowing more than one inch of leaf growth at a time.  During the summer, tall fescue lawns should really be mowed at a height of 3 ¾ inches, during the June 15th through September 15th window of the year, due to the typical heat & drought extremes of this time of year.  On severe hot/dry summers, tall fescue lawns should only be mowed when they get so tall that they are flopping over, and they should be mowed later in the evening when the sun is low and near sunset; mowing only periodically, and at 4 inches high, is best when severe heat & drought conditions exist.


The use of commercial mowers or lawn tractors should be performed with caution.  These machines are quite heavy and have large tires that are capable of ripping up well-established grass, much less young seedlings.  If these mowers are used it is important that all turnarounds are done either on a street or driveway, or in a wide arching movement at a pace about one half the normal mowing speed.





For fall seeding, care should be taken to remove a majority of leaves and sticks from the lawn as needed.  Leaves and sticks left on the lawn could smother the new grass, creating dead spots in the lawn.  It is also advisable to take the opportunity during the annual “January thaw” to remove the leaves and debris which always seem to blow into the lawn from mysterious places.  When an existing lawn is overseeded, there is usually enough grass already present to keep the leaves from settling at the soil surface.  If this is the case in your lawn, you may rake, vacuum, or mow the leaves as normal without hurting the new seed.  If you have a lot of bare soil areas, while the lawn is still germinating we strongly suggest the delicate use of a blower to remove the leaves so that there is no displacement of the seed (or young grass seedlings) from rake tines or tires.  Once the lawn reaches the point where it needs to be mowed you may also use a lawn vacuum (be sure not to set it too low!) or the lawn mower to collect the leaves.  We do not recommend the use of a mulching mower to chop up heavy amounts of leaves during the first year of the new lawn.  Large amounts of chopped leaves steal needed nitrogen from the grass seedlings and often cause small dead pockets in the lawn by suffocating the seedlings.  Hand raking is acceptable, but it must always be done very gingerly to avoid uprooting the seedlings with the rake tines.





In order to promote the healthy establishment of your new seed it is very important that a starter fertilizer be applied around the time of the seeding (within a month before or after) and a follow-up fertilization take place 4-8 weeks after the first application.  This will promote the thickening of the new areas and allow them to mature enough prior to the onset of winter to handle the cold weather stresses.  Ideally, the lawn should continue under a well-regimented lawn care program in subsequent years.  New grasses will thicken and mature more readily when there is adequate fertilization provided. Whenever a lawn is seeded outside of the fall timeframe or if it cannot be regularly watered, it is highly recommended that our Stress Reducer / Rejuvenator application (in addition to the starter fertilizer) be made soon after the seeding is completed.  This application provides naturally occurring growth hormones and plant vitamins, which aid in stress reduction and more rapid establishment of the new seed.  If you would like a price on adding this application to your newly seeded lawn, please contact our office.





Whenever the soil profile is disturbed in any way, weed seeds are brought to the soil surface where they will have a chance to germinate.  It is impossible to avoid weed seed germination while the new lawn germinates. Most of the weeds that do germinate, however, are annuals, which will die off during the next change in season.  The amount of weed activity that does arise depends on the same factors that affect seed germination.  The key to minimizing weed invasion is to establish the new grass seed as quickly as possible. By providing all of the factors desired for turfgrass germination you will inherently minimize weed invasion by developing a thick stand of turf.   If there was a significant problem with crabgrass in the months (or year) preceding the lawn re-seeding work, it is usually recommended that a crabgrass control be used the spring following the seeding. This will keep the crabgrass from getting a foothold while the new seed is still maturing. If any broadleaf weeds do get into the new lawn they can be treated once the new seed has germinated and been mowed several times. 

Note:  If your lawn requires any touch-up seeding, all weed controls must wait until the newest seed

planted has had a chance to establish and be mowed several times.  




With all new seeding work it is important to address any problems as quickly as possible so that they can be corrected, if needed, before they become severe problems.  If you encounter any situation that you are uncertain about please give us a call at (717) 299-2112 and we will be glad to help you every way that we can.  You may also e-mail us at and we will respond to your inquiry promptly.