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I want to install irrigation and turf in my backyard sometime next year. Related questions have been asked, but the focus is mostly about soil preparation.

In my case, a variety of grassy and broadleaf weeds have been established for multiple years. I know from experience that the seed stock will remain in the soil and overtake the new grass.

What can I do this year to the weeds to give next year's grass the best advantage?

USDA Plant Hardiness Zone 9b (25-30°F).

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The weeds won't overtake turf, provided you haven't left persistent/pernicious weed roots in the ground, it's grass sown from seed that will have that problem. You just need to ensure you dig out, all the roots and all, any persistent weeds such as docks, dandelions, nettles, meadow grasses and the like as part of the preparation. Annual weeds aren't such an issue - and are always with us ongoing.

If you want to try killing some of the persistent weeds this year by applying weedkiller, you can, but bear in mind, any open soil you create this year will rapidly be populated by other weeds. Nature abhors a vacuum, and empty soil won't be empty for long... Otherwise, if you live somewhere with hot summers, you can try solarization https://www.thespruce.com/soil-solarization-method-for-killing-weeds-2132941, or in colder, more temperate climates, covering the entire area with thick black plastic, tightly anchored down to exclude air, light and water, though the latter is more effective if left like that for two years rather than one.

Ultimately, you will need to dig over the whole area, clearing unwanted plants, any large debris, weeds and particularly their roots from the soil not long before laying turf. Anything with a tap root, such as dandelions, is better dug out completely by hand - using a rototiller may not get the entire root out, and will also chop up other roots and distribute them nicely all over the area - there are some weeds which will regenerate from those small pieces of root.

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  • Hey Bamboo, the more disturbance the more weeds are invited to the party. I could not have promoted getting rid of weeds AND being able to land the project. Never ever ever had a problem because perennial weed roots were able to push through to get sun. To err in bidding too low is the kiss of death. To err too high is the kiss of death. Never did I worry about weeds. Sod cutter, grading, fine tune grading, rolling, leaving the compacted soil bed alone as much as possible to then lay sod, roll again. Seeding DIY is fraught with downsides. Grass spray seed companies close that gap. – stormy Apr 15 '18 at 4:28
  • I have long been aware that your approach to turfing is not the same as the one in the UK - whether that's personal to you, or is general in the States, I don't know. But perhaps the difference is, you all pay companies to come and maintain your grass, whereas we here don't - we just make the correct preparation, then just cut, scarify, aerate, fertilize as necessary ongoing. Preferably without the use of weedkillers, other than one annual treatment if necessary, which might include mosskiller. And we never, ever, roll our lawns - only on sports turf - but our grasses are always the same – Bamboo Apr 15 '18 at 10:33
  • @stormy - sorry, should have tagged you in my comment above, or you won't know its there... – Bamboo Apr 15 '18 at 11:36
  • I realize that your lawns have as many experts as there are lawns...when working and making money commercially to maintain residential or commercial properties, to compete you HAVE to be successful. Learning how to tame that dang monster called a lawn was a full time decade of experience...hands on. There ultimately was but ONE way to have a beautiful lawn with the least work, expense and no products applied other than fertilizer. Perhaps lime. Moss killer was a bandaid for poor drainage and shade and had to be then limed before reseeding. When installing sports turf... – stormy Apr 15 '18 at 21:59
  • To compete successfully in landscape maintenance I had to communicate with my guys most knew no English. I was really good with body language..sharp sharp blades every day. I had them cleaning the mowers in between residences to not spread any disease. I had all my mowers custom raised to be no shorter than 3". A setting for 4 and 6". Using Dr. Earth's Lawn Fertilizer (with thatch eating bacteria) zoomed my services to the top in Seattle Washington. I set all the irrigation automatic timers. Never a client did leave, waiting list. We chose those who were in a neighborhood. – stormy Apr 15 '18 at 22:16
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I am constantly amazed that in all my decades of gardening, weeds have never ever been a problem..they are there, I know how to manage them effortlessly and I also know that a healthy bed of soil that makes healthy vigorous plants can do their part in weed control.

The sod being 2" over the weeds and weed seeds effectively smothers and inhibits anything other than the grass crop. Even major thistle or perennial roots. Mowing all by itself removes the top growth of any lucky weed to pop through the sod...remember no lower than 3"! There is no way I would have remained sane if all weeds had to be killed or pulled out of the soil before installation of sod, seed, hydroseed. I would have given up. Never spent any energy on weeds. Never. Never had problems or I wouldn't have been paid the big bucks, ha ha ha.

The thousands of acres of sod and plant beds I've designed, installed and maintained have proven to me that a healthy crop of grass, cool season in particular, maintained correctly, mowed no LOWER than 3", mowed 1X minimum per week, bagging clippings, aerating by pulling plugs of grass and soil and leaving them to disintegrate on top of the lawn. Training the grasses roots to grow deeply by proper watering practices, fertilizer knowledgeably added 3 to 4 times per grow season...will create a crop of grass so thick no weed seeds could germinate (too dark), proper fertilizer formulations for the time of year can prevent fungus and diseases during the winter.

Weed seeds are everywhere. In our soils, mulches, gravels, bird's poop, thatch, compost...weeds are just not a big deal. Even 'perennial' weeds with the ability to grow from pieces of root are simply plants. Easy to 'starve' out by snipping off any photosynthetic growth. Roots then decompose and become part of the TILTH of the soil. Easy to 'shade' weed seeds and baby weed plants, smother them with soil, use newspaper with soil or rocks...big deal. Weeds are just plants out of place. Usually a bit hardier than what we WANT to be growing. No water, no sun, no fertilizer...plants can't grow and logically, weeds can't grow.

Do not worry about getting the entire root out of the soil. If there is no top growth that root dies. No water. No sunlight. That root will die and become part of the organic matrix in the soil.

Get some professionals out to your site to give you estimates and lots of local facts concerning your soils. Free. Do not forget to call a hydroseed company. Very inexpensive and tons of pertinent information as you walk your own landscape. Free estimates, free advice.

I would be distressed if there were zero weeds..

Hope this helps. Pictures, please.

I've just now found you are in zone 9? Where exactly do you live? You must have warm season grasses, very different management techniques. Tougher actually than cool season grasses. Still weeds are not a deal breaker in the landscape or lawns. Knowing the basic maintenance practices (mowing height, watering, fertilization, aeration) weeds will not be a problem

Note: Since you have an entire year, go ahead and solarize. You are in zone 9. Clear plastic allows IR through to the soil and weeds yet blocks the heat from leaving. Clear plastic. Black plastic absorbs the IR itself not allowing the soil to heat up very much at all. Just cover your area with clear plastic. This will kill weeds but it will also kill all of the life in the soil as well. That can and must be built up after solarizing. You should be able to kill most perennial weeds, some seeds, some fungus.

W

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