Tell me why I'm wrong

[Fronta1]

Concerning a tttf/kbg mix - consensus seems to be to get 50:50 mix must be 90:10 by weight. From what I understand this figure was calculated using seed counts. I don't understand this. Here's my logic: as an example you want to seed 10k sq ft. If you want 50/50, is it not logical to think of it as seeding 5k sq ft with tttf, and 5k with kbg? Isn't that the definition of want wanting a stand comprised of half of each? (overlapping, obviously) so the math for that would be to divide 10k/2=5k and apply the seeding rates to each half, giving you (9x5)45lbs of tttf and (5x3)15lbs of kbg. Obviously that's not 90:10, it's 75:25.....am I missing something?

[PSU4ME]

Seeding rates vary by who you talk to but I think 1-2 pounds is a kbg range and 5-10 is for TTTF so play with any combination there and you can make 90/10 work. 75/25 or 80/20 isn't wrong but 90/10 is usually what I hear/see.

Factor in the size of TTTF and how much of it the birds eat vs the small kbg and your 75/25 might turn into something different by the time it germinates

[Jackpine]

FYI:
The 90/10 ratio appears to be based on 2,250,000 KBG seeds per lb. Not sure that applies to the elite varieties discussed on here. I don't recall seeing anything higher than Bewitched at 1,500,000 seeds per lb. 85/15 TTTF to KBG may be better.

[STL]

Look up the data sheets on the cultivars you're interested and see if they list the number of seeds per pound. Some do and some don't. Even those are approximations, but will closer. Do some research but don't overthink it. Lots of other things to do/figure out as well if you're planning a renovation.

[seiyafan]

KBG has a lower germination rate than TTTF so more seeds need to be applied.

[Jackpine]

KBG has a lower germination rate than TTTF so more seeds need to be applied.

Yup, at the mix rates discussed here we are talking in the neighborhood of 10 KBG seeds per sq inch. Factoring 80% germination that leaves 8 seeds per sq inch which should do fine. The tall fescue helps because by the time it tillers the KBG has had time to get off to a good start.

[Green]

This discussion might help too: viewtopic.php?f=4&t=14741&p=199909&hili ... th#p199909

Looks like it was also recently updated. I haven't tried to verify the math.

[Green]

Also...

Fronta1: I noticed your update in that thread. As mentioned, I haven't tried to verify your math. Does it hold true? Where did you get that formula from?

[Fronta1]

Yeah the formula was just a complicated way of saying what I said above(to do it by seeding rate, not seed count). I'm not saying I'm 100% sure I'm right,I just haven't seen the math behind the 90:10 rule. It's true exact seeding and germination rates would give you more accuracy, but the math still doesn't give you 90:10. So I'm just curious where it came from. I'm wondering if it's stand composition after a certain amount of rhizomatic spreading, but I don't really like the logic behind that either. Help!

[seiyafan]

In the Jacklin Seed website, they have "mix with 80% tall fescue" in their KBG product descriptions.

[andy10917]

I know who did the math for the 90:10 thing, and like most of the things done by the veterans around here, it was highly likely to be round number calculations that can be done in your head while you're doing four other tasks. This isn't a problem begging for calculus. It's a little more detailed/finer than "glug-count" math, but tolerant of 5% here and 3% there errors.

[g-man]

These guys did it by weight. These are comparing PR and kbg. Notice how much % kbg they had after 2 years.

https://turf.purdue.edu/tips/2007/08_03seedmix.htm

[Fronta1]

I know who did the math for the 90:10 thing, and like most of the things done by the veterans around here, it was highly likely to be round number calculations that can be done in your head while you're doing four other tasks. This isn't a problem begging for calculus. It's a little more detailed/finer than "glug-count" math, but tolerant of 5% here and 3% there errors.

If you start with 50/50 the scale will tip more and more towards the kbg as it spreads and the tttf things out. The 90:10 rule might be accounting for that to give you a balance, say, over a few years.

[Jackpine]

Another important thing to remember is how much seed to use. I went with 7lb/K a few years back on my first front reno and should have went at 6 LB/K. Also found out Tall Fescue is not intended for zone 4B as it ended up being isolated clumps mixed in with the Bluegrass after a couple winters and looked like crap. I shudder when I see it in the big box stores around here.

[andy10917]

The same thing happened here with Hybrid Bluegrass. It kept failing due to Winter here, and the seed vendors kept selling it.

[Green]

More fuel for the fire...

When I did my back reno in 2013 (there's no thread on it, because I didn't know about reno threads back then), I agonized over how much seed to use...2 TTTF cultivars and 3 KBG cultivars. I was shooting for a 75/25 % by weight ratio of TTTF to KBG...in theory. I never was able to get much of the math to work. I mixed 20 lbs of KBG seed and 40 lbs of TTTF seed (not together...they went down separately). The other thing was, I had a trusted pro do the seed down for me because that was part of the deal for the landscape work and grading that had been done. This is a guy who I've talked with a lot over the years about grass...and to be honest, I think he just went by eye more than anything as far as what spreader settings to use and how much of each seed type. I had it all calculated out on paper, and whatever he did seemed close enough. I don't know how you quantify a 50/50 mix by eye...but over 3 years later, there's definitely more KBG than TTTF in the sunnier areas...which is fine...I knew we were going fairly heavy on the KBG. That was the plan. We also used a LOT of TTTF seed, though. By the time all of the overseeds were done the following Spring (due to washout, etc.) I had used about 40 lbs of TTTF seed on just over 2K area...lol.

[seiyafan]

All sod farms here use 90/10 in their TTTF sod because the 10% KBG provide the tensile strength.

[andy10917]

Where is "here"? I'm in the same county as you and unaware that "all" sod farms are doing 90/10 or that many are even into TTTF in a big way...

[Fronta1]

Here's what's nuts about this whole thing...After doing all that back and forth and complicated mumbo jumbo, it's as simple as always using one third kbg as tttf to achieve 50/50 from the start because the avg seeding rate for tttf is 9 and kbg is 3. It never ceases to amaze me how I will run in circles when the answer is so freaking simple. Honestly, it's amazing. Then you can just take the avg seeding rate of the two, 6, multiply it by your square footage, and then you know that 3/4 of that number is the lbs of tttf you need, and 1/4 is the lbs of kbg you need. (Again, this is for a 50/50 mix in year 1.) K, done. Lol here it is super super simple

For a mix of 50/50 kbg/tttf from year one:
(Sq ft)(6)(.75)= lbs of tttf
(Sq ft)(6)(.25)= lbs of kbg

[Marinegrunt]

I bet you're right about 10% being a 50/50 mix a few years down the road. I know when I ordered my seed from Hogan's he said 10% kbg equals a 50/50 ratio. I didn't question him on it though because it seems to be the consensus.

There are posts where people have really dug into it to get the ratio they wanted. One example mentioned using 3 different types of kbg. If you just took a 1/3 of each your yard could end up having much more of one of the cultivars because of seed size. Your talking tens to hundreds of thousands more per pound so you can see how you would have more of one seed. If you want to get as close as possible you have to take seed count into consideration and calculate from there.

You mentioned you weren't a fan of kbg but wanted it for the benefits it adds. That's pretty much the same I'm doing for our lawn this fall. I personally like kbg better but was worried about some shady areas. I let my wife decide after showing her pictures of different lawns and she liked the tttf. I then decided to add 10% kbg so it could spread and knit with the tttf and hopefully keeping me from having to overseed or atleast as often.

If you're just doing an overseed I personally wouldn't worry about the percents too much.