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Fertilizing the Lawn in Late Summer or Early Fall

Cool season grasses are the main components of a desirable home lawn and include Kentucky bluegrass, perennial ryegrass and creeping red fescue. These grasses go through a dormancy period in the heat of the summer. This means that root growth essentially stops and the tops turn brown. Watering the lawn through periods of heat and drought will prevent complete dormancy and keep the tops growing.

In the late summer and early fall, root growth begins again because of the decrease in soil temperature and increase in natural rainfall. The grass will green up again with the production of new roots and shoots and damaged patches will start to disappear. Fertilizing at this time will provide the nutrients the grass needs to recover and re-grow rapidly.

The fertilizer you apply in the late summer will be used up by the plant to grow shoots and roots, rather than being stored in plant tissue for use in the future. Late fall fertilization, on the other hand, is mostly stored in the roots for use the following year. Late summer fertilizer should be high in nitrogen with at least 50% of the nitrogen in the form of slow release. It should also contain potassium since this is important for the production of vigorous and hardy plants.

Sulphur-coated urea is the most common source of slow release nitrogen and will spread the availability of nitrogen over a 6-week period. Other forms of slow release nitrogen are also available which will spread the release over an even longer period and at a more predictable rate. IBDU, or isobutylidenediurea, is one of the best choices since it is the most environmentally "friendly" nitrogen available. It has a low burn potential and low leachability. This means that it will not harm non-target areas and will provide nitrogen at a slow and steady rate to the grass. Polymer coated nitrogen is another form of slow release nitrogen which is gaining in popularity due to its clean handling and long-lasting performance.

Blends such as 24-4-12 or 24-4-8 good choices for late summer fertilization. These should be applied at the rate of 3 - 4 lb of product per 1000sqft. (1.5- 2kg per 100sqm) in order to provide 3/4 - 1 lb of nitrogen per 1000sqft.

High potassium blends such as 12-8-16 can also be used, particularly if potassium has not been applied before. These lower nitrogen blends should be applied at 5-6 lb per 1000sqft.

If you are unsure about how much fertilizer you need, measure the lawn area, take the measurements in to the garden centre and ask for help.

Don't be tempted to spread the fertilizer by hand since the result is often uneven, patchy growth which takes a long time to repair. Use a spreader which can be borrowed or rented from the local garden centre. Four pounds of fertilizer per 1000sqft. is fairly sparse coverage, so you are well advised to do it properly in the first place to save yourself time and money.

It is preferable to fertilize a day or so after cutting. This way, there is no risk that the lawn will not be cut due to delays by rain or a busy schedule. The fertilizer will stimulate new growth and too much new growth prior to the next cut will be detrimental to the lawn. Natural rainfall should be sufficient to water in the fertilizer and make it available to the plants. The higher content of soil moisture in late summer, combined with the use of slow release nitrogen, will prevent the risk of fertilizer burn.

If your lawn is full of weeds and bare patches due to disease or insect attack, fertilize anyway. The weeds can be easily controlled by using a broadleaf herbicide at a later date or to combine the fertilizing and weed control by using a granular "weed and feed" product. Many weeds can be controlled by simply promoting grass growth and regular mowing.

The bare patches can be seeded after fertilizing and roped off if need be until the new grass germinates. Late summer is an ideal time for re-seeding because the soil is warm and natural rainfall should keep the seedlings well watered.

Promoting the re-growth of grass in late summer through fertilizing, frequent mowing, weed control and re-seeding will repair any injury caused by a hot, dry summer. This new growth will be well on its way to survive the winter stresses ahead.

Daisy Moore, 1999.




Other autumn garden tips:

(click on the tip you want to read)


Fall Perennials
Planning New Beds for Fall Planting
The Garden in Transition
Dividing and Transplanting Perennials
The Dos and Don'ts of Staking Trees
Re-Seeding or Sodding the Lawn
Bulbs: Always Worth the Effort
Fertilizing the Lawn in Late Summer or Early Fall
Preparing the Vegetable Garden for Next Year
Growing Garlic ...For Food or Ornament
Priorities for Fall Gardening
Preparing the Garden for Winter





Home  |  Garden designs  |  Naturalized gardening  |  Help with your garden  |  Garden Tips Spring  Summer  Fall  | Contact Daisy


Daisy Moore 2006