Weed n' Feed in late fall

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May 25, 2005
Calgary Canada
I normally hit the lawn with weed and feed pellet fertilizer/herbicide in October. I forgot, and we've had one small snowfall. Temps are lingering around freezing or a little below right now, but temps are supposed to be close to 45 later this week. Is it advisable to spread fertilizer this late in the season? I've got a good stockpile, so if it won't do any harm, I plan to do it. Can anybody offer some thoughts here?
The Feed and Weed I have used over the years calls for application in the spring or early summer + what most people don't understand that when you apply the application is that the grass must be wet so the stuff sticks to the leaves of the weeds to kill them. The instructions on the bad should mention this and other application issues.
@SrDriver: I just used my Scotts Winterguard in late October in Montana. In the reading I've done for lawncare, you'll probably need to do it more than once per year anyway. Also, the weed n feed you do in the fall is supposed to do quite a bit of good for the following year's grass.
Around here, the smart ones put a weed/feed down at the end of Dec or early Jan. But our weather is completely different! It helps eliminate weeds popping up before the grass, usually around April/March.
The temperature matters a lot. Especially the weed killer, if it's below a certain temp, it won't help. Likewise, if the grass has gone dormant, I can't see how the grass is going to use the food. It's just going to wash away below the root zone over the winter.
I just noticed... Calgary! I'm 800 miles directly south of you. Anyway, fall feeding is very important. For me, that means September! You could do it, but if it were me I'd wait and hit it good in the spring.
It's very difficult to judge what your climate is there, which determines how late you can do a late season application. But I'm going to guess that you are on the edge of being too late. I can't imagine that you get the ocean warming effect like western Washington and Oregon. You want to schedule late season fertilizing when the top growth has just about ceased, but the roots are still active. Root activity begins to slow down when soil temps. drop below 45F. Late season fertilizing usually is with nitrogen only, and usually with a fast available type, i.e. urea. You are in about the same situation regarding the broadleaf weed control. While fall is best due to nutrient allocation to the roots, you need the tops to be active enough for the chemical to translocate to the roots. This publication is from Ohio and recommends late October for northern Ohio: http://turfdisease.osu.edu/turf-disease-updates/benefits-late-fall-fertilization . This would be about the last week I would try it in southern Michigan. Contact your ag. university up there or "maybe" some lawn care companies to get their opinion (although they might try to sell you a service, regardless. To others, read my link to learn about late season applications.
From what I understand, as long as the ground is still warm, the grass is extending it's root network in the fall and early winter. So feeding is useful. I aerated and over-seeded in mid-September, so no weed killer for me. I amended my soil in bare spots, digging out the tough Central IL clay and replacing it with some topsoil to give the new grass a better place to take root. Other places simply got seed without anything other than the aeration. This was my 4th season with the new lawn. The property is almost filled in. The builder took most of the topsoil when they built the house. Clay is not horrible as it has lots of nutrients. It is simply a tough place to get things started. What I really need is about a million earth worms to do their magic. Sorry, I digress. Weed and feed does work in the fall as your grass is still working underground. How late depends on where you live. Calgary, isn't it frozen solid there now smile
Herbicides can be extremely effective in the fall especially during the first couple frosts. I find fall herbicide applications actually work better on perrenial weeds compared to spraying in the spring. Weeds are trying to store energy to the roots from the top growth when it turns cold thus pulling the herbicide down to the roots with it. I also do fall fertilizer on my hay fields that are too wet to get on in the spring. Still effective especially if the soil lacks minerals but I find nitrogen works better in the spring application.
While it is supposed to hit a high in the mid 40's (F) for 2 days this week, the extended forecast for Calgary predicts below average temperatures: Barely reaching 32F in the day and in the lower teens (F) at night, with chances of snow flurries on many days. Not too promising, in my opinion. http://www.theweathernetwork.com/fourteenday/caab0049/table?ref=tabs_14day_table 0C = 32F -11C = 12F This is not frost weather, but rather hard freeze conditions. Save your weed and feed for next year, in my opinion.
In Florida, which I'm not sure if this is applicable to colder states, the yard is really a make or break based on what you do during winter. I mentioned the weed/feed in late Dec or early Jan, but people that have really nice lawns here usually water at least once every 2 weeks even during winter time, unless it goes below freezing. Many use seasonal grass as well (like rye grass) to keep weed growth down. The rye will live long enough to avoid weed propagation then die off once it gets hot. Usually another weed/feed is done again by March/April to avoid new growth of weeds. I typically also add in a natural fertilizer sometime in June/July (usually Mylorganite). I typically do not use another weed and feed for the rest of the year, because weeds cannot survive the heat, but the grass can.
At this point in the season and taking into account where you live I would NOT use a growth based weed and feed. What you want to do is apply a winter fertilizer designed to feed the roots and not encourage top growth. When spring arrives the grass will be well rested and ready to grow since the soil/roots have been prepared with the winter formula. After the first few warm days of spring then I would apply the weed and feed.
In the midwest and northern states, its generally not recommended to apply an early spring fertilizer application. Top growth takes off in the spring supported by nutrients stored the previous fall. Additional early spring fertilizer causes excessive spring top growth that encourages disease, excess thatch, etc.. An exception would be if you were trying to refurbish a stressed and weak turf. Broadleaf weed control will work in the spring, but again you are fighting the natural physiology of the plants....nutrients are moving more up to the tops, rather than down to the roots, where you want the herbicide to go.
doitmyself echos what others have told me. I use an N-P-K of 6-24-24 to feed the roots every November in SE Michigan. The weed application I use is a broadleaf weed killer in the springtime. As SrDriver mentioned, it must be applied when the lawn is wet so it'll stick on the leaves, and the lawn must be rain-free for at least 24 hours so the stuff won't wash off. I was told the vigorous growing action of the broadleaf weeds is what helps the chemical work. I don't fertilize in the early spring because lawns don't need it. They're very vigorous with the first flush of growth.
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