ADJUST AUTOMATIC SPRINKLER SYSTEMS
The hot, dry August weather has made it necessary to increase the amount of irrigation needed to keep lawns green. Continued warm conditions are predicted for the first half of September. Then, almost overnight we will find that plant water needs are decreasing as weather cools and days become shorter. As soon as daytime highs drop consistently into the 70’s, you can reduce irrigation frequency.
The best way to decrease irrigation is to lengthen the interval between irrigations. Daily irrigation is always too frequent at any time of year unless you are starting new plants or a new lawn. Daily irrigation causes plants to have shallow roots because the soil is always dry except the top fraction of an inch. Keeping the top of soil moist also encourages weed seed germination. If you have been watering on a 2 day interval, the best adjustment would be to change the interval to 3 days. If your interval is 3 days, adjust it to 4 days.
In general, enough water should be applied in each irrigation to reach a depth of 6 inches. This varies from about ½ to ¾ inch of water. The length of time needed to apply this much water depends on several factors including the type of sprinkler heads, pipe size and water pressure.
An easy way to check water output with your specific sprinkler system is to place shallow cans such as tuna fish cans on the lawn or ground and turn the water on for a specific amount of time such as 30 minutes. Measure the amount of water accumulated and then calculate how long it will take to apply ½ inch.
By placing several cans at different distances from sprinkler heads, you will also discover how uniformly your system applies water. You will probably find that some areas receive twice as much water as others. If differences are too great you may want to contact a sprinkler contractor to adjust or update your system.
The best time of day to irrigate is between midnight and 7 am. Water loss due to evaporation is much less when the sun is not shining. Plant diseases are less when plant leaves are not wet for more than 6 hours. Sunlight right after irrigation allows leaves to dry out quickly.
THIRSTY TREES AND SHRUBS
If you have not watered trees and shrubs this summer, it is time to give them a drink. We have had almost no rainfall for well over a month. A deep watering which gets moisture a foot into the soil is in order. An inexpensive drip irrigation hose is a great tool for deep watering. Simply snake it around a tree or between a group of shrubs and let it run for several hours or overnight. With the slow application rate, there is no runoff even on the hardest clay soils. Check with a shovel to see how deep it has penetrated. Remember that most of the water absorbing roots are under the outer edge of the branches.
This is the best time of year to plant new lawns or over seed old ones. The warm soil and cooling temperatures are ideal for grass seed germination. If you can keep the top of the soil continually moist by irrigating several times per day, you will have quick results now. If you do not have an automatic system or can’t be home for frequent light sprinkling, then wait until rains start in a few weeks.
We have been very successful using a 4 step system to eliminate the coarser wild grass patches in established lawns. We spray Roundup to kill the ugly patches. Then 2 to 3 weeks later we apply a ½ inch layer of top soil over the dead patches. We scatter seed and fertilizer on the soil and rake lightly so most of the seed is covered. An extra step may be helpful if you cannot water several times a day. A thin layer of fine bark dust or peat moss will help retain the moisture in the soil.
The importance of getting the seed in good contact with the soil is critical in over seeding. You can loosen the soil with a rake, but applying a thin layer of soil is more effective.
IDEAL TIME TO FERTILIZE LAWNS
September, October and November are the best months for fall lawn fertilization. When you fertilize during this time period depends upon the condition of your lawn. If you have not watered your lawn this summer, fertilize as soon as the rains start. If your lawn is green and growing well, wait a month or so. Fertilizing in October or early November will keep your lawn beautiful through the winter without increasing the growth rate.
One of the great benefits of fall fertilization is that it not only gives immediate results, but it also carries over into spring. Fall is the time when grass makes a lot of new growth under the ground. New roots and crowns cause turf to thicken. Food produced by the leaves is stored for the winter and next spring.
Most brands of lawn fertilizer have developed formulas for fall fertilization. They generally contain more potassium which makes grass more resistant to winter weather. However, I have found that almost any lawn fertilizer works well in the fall. Research has shown that nitrogen is taken up by grass roots and used to make amino acids which are stored in grass crowns and roots. These amino acids are available for immediate use in early spring when soil is too cold for roots to take up nitrogen. The result is a more attractive spring lawn.
Read the “guaranteed analysis” label to make sure lawn fertilizer contains iron. Iron causes grass to turn dark green, sometimes almost over night.
Fall is also an excellent time to apply lime to lawns. I like to lime my lawn every 2 to 3 years to reduce soil acidity.
Wait until late November to fertilize trees and shrubs. By then, top growth has become dormant, but roots can continue to take up fertilizer. Stimulating new growth now will make some of our more sensitive broad leaf evergreens more susceptible to winter damage.
FALL IS A GREAT TIME TO PLANT
Now through November is the time to plant spring blooming bulbs such as daffodils, tulips, crocus and hyacinths. I have had the most success with daffodils. Moles and squirrels do not eat them and they multiply so that you have more flowers every year.
You will find Mums and Fall Asters in bloom now. Now is a good to plant other perennial flowers, container-grown trees, shrubs, vines and ground covers. If you want to move plants in your own landscape, wait until November.
Pansy is the ideal annual flower for fall, winter and spring bloom. Planting in September will give plants time to become established before cold weather.