To Do List: Fall or
Early Spring
The easiest way to start the move towards organic lawn care
is to make sure your lawn is really healthy. All of the regular seasonal lawn
maintenance chores are therefore excellent ways to go. Those chores are summarized
here.
Remove Thatch Thatch is that layer of stems, roots and dead
organic matter you can see when you part grass stems. A thick layer of thatch
suggests overuse of synthetic pesticides or fertilizers, since these tend to
kill off the micro-organisms that help organic matter to decompose.
Thatch only becomes a
real problem when the layer is thicker than a half inch, at which point it can
become a breeding ground for insects and for various fungi, and a barrier in
the way of water absorption. If you scroll through a page on fighting lawn
problems, again and again you will see advice to remove excess thatch.
Clippings often get
blamed for thatch, and people rake clippings because they don't want to
contribute to thatch build-up, but this is a false problem with a non-solution.
Clippings only contribute to thatch if they are excessively long or if the
thatch layer is so deep that it keeps clippings from decomposing.
Even a thin layer of
thatch should be broken up or removed every couple of years, to prevent it from
building up past that point. For everyday thatch of less than half an inch in
depth, use a garden rake or a tool designed for removing the matted material.
Top-dressing (adding a thin layer of something on top, rather than digging it
in) with soil or compost can also be helpful, as both these materials contain
microorganisms that will help the thatch to decay. For regular seasonal
maintenance, these are all that should be necessary, and on many lawns they may
only be necessary once a year or even less. Just check the thatch level each
spring and fall.
For more serious
thatch buildup, you may need to rent a vertical mower, a specialized machine
that works vertically to break up and remove buildup.
Unfortunately, a
vertical mower can be so hard on the rest of your lawn that you'll often need
to reseed after using one. Anything that hard on the lawn should only be used
in spring or fall, when grass recovers more quickly than it can in the heat and
stress of summer. Spring and fall are also the best times for overseeding, of
course.
An alternative approach is to remove as much thatch as you
can manually, then aerate like crazy and top-dress generously with compost.
Aerating breaks up some of the thatch, while compost adds micro-organisms that
help decompose what's left. If you do this in spring and fall, you may well be
able to bring even a thick layer of thatch under control without resorting to a
vertical mower.
Aerate Aerating removes plugs of soil, which helps
reduce soil compaction, one of the most frequent problems of older North
American lawns. It also opens the soil to fertilizer, amendments, and seeds, so
it is an excellent preparation for other seasonal care.
You can buy a home
lawn aerator tool, rent a bigger, mechanized version, or hire out the job. It's
important to cover the lawn several times in more than one direction, so that
it gets thoroughly and evenly aerated.
Amend Soil Soil amendments actually improve the soil's
ability to supply nutrients, water, and air to plant roots. The movement or
availability of these three essentials can be inhibited by compaction, high
clay or sand content, and high or low pH. All of these are soil conditions
independent of nutritional content, but they have a direct bearing on whether
nutrients can be taken up by a plant.
Many amendments do
supply nutrients, but their primary purpose is to improve soil texture and
structure.
Spring and fall are
the ideal times to apply soil amendments, but lighter doses can be put on even
in mid-summer. Before you start adding lime or sulfur, however, test your soil
pH (or have it done) so you're sure to be adding the right thing.
Here's a quick and
dirty overview of amendments. The knock-down drag-out version is under our
Guide to a Healthy Lawn.
Compost: If
you're not sure what your problem is, add compost. For that matter, even if you
are sure, add compost. Compost is the miracle amendment, for it improves all
soils. It helps balance pH, making acidic soils more alkaline and alkaline ones
more acidic. It improves soil retention in sandy soils and drainage in clay
soils. Used regularly, it helps reduce compaction. It contains micro-organisms
which help organic matter decay, keeping thatch under control and ensuring that
clippings will in fact disappear, and not lie around in an unsightly fashion.
For Sandy Soils:
Organic additions work best to improve drainage and relieve compaction in sandy
soils, because organic matter derived from plants and animals holds many times
its own weight in water. Compost adds much more than organic matter, being rich
in nutrients and micro-organisms, but for sheer unadulterated water retention,
peat and sphagnum moss or coconut fiber cannot be beat. Mature, composted
manures -- not fresh manure! -- are also excellent.
For Clay Soils:
Surprisingly, everything said about sandy soils goes for heavy clay soils as
well: organic additions will make the greatest difference. Sand and gypsum are
frequently suggested as amendments for clay soils, but many experts question
their effectiveness, and they need to be used carefully. (For more on these
debates, see Soil Amendments on this site.) With products derived from plants
and animals, you cannot go wrong.
To Raise pH (make
acidic soils more alkaline): Add lime, which is available in a number of
forms. For lime to be effective, two requirements must be met: it must be
dampened; and it must be in direct contact with the soil. The necessary
chemical reactions cannot take place without water, and because lime is not
especially water-soluble, it will not be carried by water into the soil.
Pelletized lime is the easiest to handle and to apply, but
not the cheapest, as it is a refinement of one of the simplest mined forms.
Those forms are calcitic lime, which will also add calcium, and dolomitic lime,
which will provide both calcium and magnesium. Both are sold as very fine
powders, like all lime save the pelletized.
Other forms of lime
-- marl, hydrated lime (slaked lime) and burned lime (quick lime) are not good
options for lawns: the first contains various impurities, while the others are
so highly concentrated that they can be dangerous to handle and will burn
established lawns.
To lower pH (make alkaline soils more acidic) Add sulfur,
which, like lime, comes in several forms. For ground rock sulfur, add 1.2
ounces per square yard to sandy soils, and 3.6 ounces per square yard for any
other soil.
A number of organic
(plant-derived) products will also lower pH, among them peat moss, organic
cottonseed meal, and even animal manures, but none of these works as
effectively as sulfur.
Fertilize Spring and fall are the ideal times for
fertilizing, especially in the north. Summer fertilizing is less of an issue in
the south, where warm-season grasses that continue growing all summer are the
norm, but in the north, most lawns have cool season grasses that go dormant
during hot weather. Over-stimulating them during this phase just leads to
problems, so go lightly.
For quick results,
use fish emulsion, a quick-release, organic, nitrogen-rich fertilizer that can
be sprayed or sprinkled. DON'T APPLY FERTILIZER AT MID DAY, and DON'T USE MORE
THAN IS RECOMMENDED, especially in hot, sunny weather; that "cure"
will definitely be worse than the disease, as nitrogen + sun = burned grass.
Quick-release fertilizers don't last long, so give your grass another dose a
couple of weeks later.
For summer-long
results, use a slow-release fertilizer such as organic cottonseed meal, corn
gluten or blood meal in autumn and again the following spring (see Organic vs.
Synthetic Fertilizers).
WARNING: Don't use corn meal within several months of reseeding your
grass, as it also kills seeds.
Overseed This term refers to seeding over an existing
lawn. It's a great way either to fill in bare spots or to gradually change your
grass type.
If you've got a
standard-issue lawn, chances are the grass itself is not one best-suited to the
region where you live, which makes all lawn care a challenge, organic or not.
Overseeding lets you add a better-suited grass to your lawn without requiring
that you start over from scratch.
Preparation
Mow your grass as short as your mower will let you. This
will give the seeds better access to the soil below and more light once they
sprout. It will also stress the old grass a bit, giving the new type a fighting
chance to establish itself.
Remove thatch if you've got a thick layer. For seeds to take
root in soil, they must touch it. A thick layer of thatch can be a major
obstacle to successful overseeding, so if you've got one, you're going to need
to get rid of it.
Aerate to improve soil structure and to give seeds a better
chance of rooting in soil.
Often, a brisk raking
will loosen thatch and soil sufficiently. This may be all you need to do after
mowing.
Seeding
A number of different
sources recommend seeding much more thickly (up to one and a-half times as
thickly) as recommended for whatever seed you're using. This is particularly
good advice if you're trying to replace one type of grass with another. The
undesired grass already has a serious head start, and over-seeding (seeding too
much) can help to correct that discrepancy. Using a slice-seeder will ensure
that seed is deposited into soil at the correct rate.
Follow-Up
For best results,
topdress by sprinkling compost, topsoil, peat moss or coconut fiber over the
newly seeded lawn, then water until the soil surface is dampened everywhere.
The soil amendments will give the seeds a boost, and will help retain water
over and around the seeds.
If you don't
topdress, rake the ground lightly to bring seeds into better contact with soil,
then water.
Care
Keep the soil surface
damp while seeds are germinating and while seedlings are young and new. This
probably means twice-daily watering on days without rain.