How much will you miss outdoor gardening in the next few months?

Having asked ChatGPT:

“With September approaching, the poa annua battalions are preparing to invade my lawn which, recovering from the recent aggressive drought, has needed repairs and overseeding, making the use of fertilisers or herbicides problematic. What would be your best advice?”

This was one of the answers:

“4. Prevention Without Hurting New Seedlings

The classic route is a pre-emergent herbicide, but standard ones (like prodiamine or pendimethalin) will also stop your desired grass seed from sprouting. Since you’ve overseeded, you have a couple of options:

• Siduron (Tupersan) — one of the very few pre-emergents safe for use at the same time as seeding cool-season grasses. It won’t block your new turf but will suppress poa.
• Tenacity (mesotrione) — technically a pre- and post-emergent; safe on many cool-season seedlings when applied per label. It can bleach poa annua seedlings and give your new grass a head start. Needs follow-up applications.”

I am intrigued because general advice (including on this forum) has always been that nothing could be done against poa annua and (at any time or in any case). I had never heard of either Siduron nor Tenacity Mesotrione; they sound like early Christmas.

Has anyone experience of obtaining or using these? Go on, make my day!

 

Hi @LawnAndOrder I suspect these are restricted to professional use, as pre-emergent don't seem to be retailed. However if you're old enough (like me!) you can order online using "grandfather rules" - there's a strange cut off ages beyond which you're allowed to buy for private use on your own land

 

Thank you very much for that @CarolineL; sadly, this rule has expired in 2015; you may be interested in ChatGPT's response (I must confess that to undergo the relevant training, even though I would love to cross that river, is a bridge too far! (By the way, I am probably old enough to be your father, but have never acquired enough maturity to feel any older than seventeen!)

From ChatGPT:

What Should Your Forum Respondent Do?
If they truly were born before 31 December 1964 and wish to continue using professional-use pesticides:

1. They need to obtain a recognized Certificate of Competence:
   
   • Specifically, they can take the “City & Guilds Level 2 Award in the Safe Use of Pesticides – Replacing Grandfather Rights”. This qualification acknowledges experience and enables lawful use on their own land Voluntary Initiativenptc.org.uk.
     
2. Alternatively, they could:
   
   • Use amateur (home-garden) pesticides, which don't require certification.
     
     
   • Or hire a qualified contractor who already has the appropriate certification to carry out the application Game & Wildlife Conservation TrustVoluntary Initiative.
     

Suggested Forum Reply
“Thanks for the tip—though that ‘grandfather rule’ actually lapsed back in November 2015. Since then, everyone must hold a proper Certificate of Competence to purchase or apply professional-grade pesticides—even on their own land. If you were born before 31 Dec 1964, you can still get a special Level 2 ‘Safe Use of Pesticides – Replacing Grandfather Rights’ certificate to continue legally using those products on your land. Otherwise, you'll need to use amateur/home-garden products or hire a certified contractor.”

 

Oh good grief - I'd better get certified (no nasty comments please!)
I looked this up on the .gov website, well after the date it lapsed, and the page I found made no mention of the lapse.

 

Nasty ... moi ... as if, certainly not, certified or not.

Well, yes, re: lapsed information, ChatGPT seems pretty up to it speed [20 billion pieces of information per second]; (even though it has lapses, I think Mrs Lao [who has this knack of giving one the impression that she is the most intelligent thing on the planet] has met her match).

Of course, you yourself, as a Software engineer (retired or not), can probably beat ChatGPT at chess!

By the way, what is the problem with these products, that they can be used industrially but not in small doses?

 

Not regarding herbicides apart from glyphosate I have managed to purchase insecticides online that you wont find in the garden centre.
Usual problem Is the price and dilution rates, its expensive and makes about 1000gallons.

 

I'd do anything, and never let up, to get some Tenacity; I don't mind a thousand gallons, I'd used eight litres (of dilution) and I know quite a few people (not on the forum) to whom I would give the rest to drink.

 

Tenacity, not heard of that one.

 

From a reliable, if verbose, source (see above 2:52 PM):

"The classic route is a pre-emergent herbicide, but standard ones (like prodiamine or pendimethalin) will also stop your desired grass seed from sprouting. Since you’ve overseeded, you have a couple of options:

• Siduron (Tupersan) — one of the very few pre-emergents safe for use at the same time as seeding cool-season grasses. It won’t block your new turf but will suppress poa.
• Tenacity (mesotrione) — technically a pre- and post-emergent; safe on many cool-season seedlings when applied per label. It can bleach poa annua seedlings and give your new grass a head start. Needs follow-up applications.”

 

I think it's the classic "health and safety". They assume that professional users will be wearing PPE and know how to use it. For example you can get a ticket to spray certain glyphosate versions near watercourses, but I can't see how it can be made safer for the stream. That's why I inject it directly into the stems of knotweed near my stream rather than spray. (Knotweed seems to be everywhere in the local countryside)

 

Good for you.

You are spot on there. Further to all this, and responding to the deep frustration of not being able to get the very thing I most need in autumn and spring (as well as being puzzled by the fact that something so endemically desired is so universally unavailable!), I have now read up on it extensively.

It transpires that, mainly in the USA (and Great Britain followed suit), large companies have indeed tried to supply the domestic market with small doses of the above-mentioned pre-emergent herbicides; apart from the amount of red tape (environmental concerns, as you mentioned, being high on the list) there were too many associated problems: accurate dilution in small quantities is difficult, resulting in treatment being ineffective if underdosed, or causing whitening of the grass if overdosed, both drawing complaints from customers who claimed that the products did not work, or worked too well and ruined their lawns. The retailers decided that the game was not worth the candle, and thus, once and for all, was the subject snuffed.

 

If you are keen to get rid of poa annua it might be worth getting the C&G certificate. I will investigate and let you know re cost of the test

 

Probably cheaper to get someone in, lots of so called lawn experts out there.

 

Thank you, I contacted a few; pre-emergent herbicides are definitely a no-no in this country; if some use it, they don’t admit to it; the advice from the AELTC is Just get on your hands and knees and pull out the poa annua with tweezers! … I was impressed. I relayed this to Mrs Lao, thinking she would jump at the chance. She was less impressed.


My sempiternal problem remains: possibly because of the location and conditions) I am regularly repairing and overseeding which precludes the use of recommended seasonal fertilizers; it would therefore seem that the regular use of Pre-Seeding Fertilizers (such as produced Nutrigrow from Agrigem [as once recommended by LizThePot]) would be best.


To end on a happy note, I am posting two photos of our lawn which we had thought had been irretrievably lost, as it really looked yellower than the Sahara, dryer than hot sand, and deader than old straw. We just cannot believe how well it bounced back after a few days’ rain:

28th of July 2025:


14th August 2025:

 

@LawnAndOrder , that is one heck of a transformation, surprising what rain can do. Just shows how resilient grass is. I’m pleased for you, as now you can just enjoy it again without worrying about what you may need to do with it./ to it.