The Grass Doctor

When you plant grass seed, when can you fertilize, and when can you use a chemical to kill weeds?

I have to replant my whole back yard and I have never had to do this before. I am not sure of the type of planting and feeding cycles to use at different seasons. Such as, when to fertilize and when to use a weed be gone chemical.

Public Comments

1. Now that's a big job! 1 - Start with a soil test available from your local extension agent - this site will help you find the office nearest to you: www.csrees.usda.gov/Extension/USA-text.html 2 - With the results of a soil test you'll know how much your need in the way of soil amendments and fertilizers. Some slow-release fertilizers can be mixed into the soil with sterilized compost (no weed seeds or fungal spores) as you prepare the soil for seeding. 3 - Buy the best seed you can afford; choose the kind suited to your location, needs and wants. If you have kids, think fescue in the north, or zoysia in the south; Kentucky blue grass is gorgeous, but labor intensive. 4 - Seeding is best done in the autumn when air temperatures are cool, but there is the possibility of gentle rain. Small amounts of irrigation are necessary to supplement the rain. The seeds can not dry out! 5 - Some people use "straw" to cover the seed. Unfortunately "mulch hay" is often confused with "straw." Real straw has no seed heads, no seed to compete with grass seed. "Mulch hay" makes a mess of a new lawn because it will be chock full of seed that will sprout in your new lawn. 5 - "Weed-Be-Gone" and "Round-Up" are all-purpose, systemic, contact herbicides that kill everything. These are the last items you want to use on your lawn. 6 - If you've done all the steps carefully and have not introduced any weed seed, there should be no need for any herbicide in the first or even second year. After that if you have crabgrass or other annual grasses in your lawn, you might like to use an annual grass pre-emergent. For broadleaved weeds - plantain, dandelion, etc - choose a contact for broadleaved weeds, but use on windless days and keep away from shrubs and other broadleaved plants. This is a big job, but when tackled slowly and methodically, it leads to an enjoyable and usable part of your home landscape. Hope this helps.
2. Check out the Turf grass papers on the Purdue Ag Website. http://www.agry.purdue.edu/turf/publicat.htm specifically this one. http://www.agry.purdue.edu/turf/pubs/AY-3.pdf AY-3: Establishing Lawn Areas From Seed Seeding Seed should be applied using a drop spreader because rotary spreaders do not disperse the seed uniformly. However, spreaders typically do not come with calibration information about seeding turfgrasses. The easiest way to apply seed uniformly is to set the spreader adjustment very low, sow one half of the seed in one direction, and then sow the other half at right angles to the fi rst direction of seeding. It might take three or more passes over your lawn in a single direction, but it is well worth the time to get a uniform seeding. Seeding rate recommendations are presented in Table 2. After the starter fertilizer and seed have been applied, the area should receive a light raking followed by a light rolling to ensure good seed-soil contact. A roller designed to be fi lled with water, but left empty, is perfect for this job. It is critical to maximize the seed-soil contact for quick germination and establishment. Mulching Mulching the area will prevent erosion and conserve water. Therefore, mulching is most important when it is impossible to adequately irrigate newly-seeded areas. One bale of clean (weed-free) straw per thousand square feet will give a light covering that will not have to be removed after germination. Many homeowners apply too much mulch, which can shade seedlings and require removal later. Apply the mulch very lightly so you can still see approximately 50% of the soil through the mulch layer. Some professionals use hydromulch which is a paperbased mulch blown on the soil by a specialized sprayer, which is an ideal method. Watering Seedlings are susceptible to desiccation, and the seedbed should not be allowed to dry. A newlyseeded lawn will need to be irrigated two to four times daily depending on the weather. Water frequently enough to keep the top 0.5 to 1.0 inch moist, but avoid over-watering and saturating the area. Once the seedlings are two inches high, gradually reduce the frequency of irrigation and water more deeply. After the turf has been mowed two or three times, deep and infrequent irrigation is most effective. Refer to AY-7, Irrigation Practices for Homelawns, for more information. Mowing Mowing a new lawn will encourage the turf to fi ll in quickly. Mowing should begin when the fi rst few seedlings are tall enough to mow. You may only mow 10% of the plants in the fi rst mowing, 20-30% of the Soil test values New sod or seed Annual applications range ppm lbs P/acre (lb. P2O5/1000 ft2) (lb. P2O5/1000 ft2/yr) low 0-13 0-25 1.5 1.5 medium 13-25 26-50 1.0 1.0 high 25+ 51+ 1.0 0.0 Table 1. Purdue University ‘s 2005 phosphorus recommendations for newly planted turf and for annual fertilization of established turf. New seedlings have poorly developed root systems and thus they cannot effectively absorb nutrients from the soil. Therefore, it is important to fertilize frequently after seeding to encourage establishment. Apply 0.75 to 1.0 lb N/1000 ft2 four to six weeks after germination and again eight to ten weeks after germination. Assuming seeding in mid-August, these applications would be mid- to late September and again mid- to late October. For more information on fertilizing lawns, refer to AY-22, Fertilizing Established Lawns. Weed Control There is little weed pressure in the fall so weed control may not be needed. Broadleaf weeds may become a problem in the fall, but these can be easily controlled with a broadleaf herbicide application in October or November, after the third or fourth mowing. Avoid using broadleaf herbicides in newlyseeded areas until seedlings have been mowed at least three times. Quinclorac and carfentrazone are the only broadleaf herbicide that are safe to use on seedling turf. Annual grasses such as crabgrass can be easily controlled with preemergence herbicides applied in the spring. With dormant seedings or seedings made very late in fall where the lawn is not fully established by winter, avoid applying a preemergence herbicide in early spring because it may damage latedeveloping seedlings. In this case, consider using a postemergence crabgrass herbicide later in summer to control crabgrass. Do not use preemergence crabgrass controls (except siduron) at the same time as a spring seeding. As a general recommendation, delay use of these materials until new seedlings have been mowed four to eight times, depending on the herbicide. Check the herbicide label for exact recommendations. Siduron is the only preemergence herbicide that can be used at the time of seeding, but will only control crabgrass for only 3 or 4 weeks. Quinclorac can be used for postemergence control of summer annual grassy weeds in seedling turf with little risk to the desired seedlings. Always apply according to label instructions, and refer to AY-10, Control of Crabgrass in Homelawns and AY-9, Control of Broadleaf Weeds in Homelawns, for more also check this page for other Purdue Landscaping and Garden info. Most are geared towards the midwest. http://www.hort.purdue.edu/ext/garden_pubs.html