Everything you need to know about Primo Maxx

Primo Maxx

What is it?

Primo Maxx II works by suppressing gibberellic acid, the hormone responsible for vertical growth in turf plants.

The more product in the plant, the greater the suppression. Gibberellic acid is kind of like growth hormone for us humans, when conditions are right the plant shoots up in height

(but the plant doesn’t get a deeper voice and mood swings to go with that vertical growth).

When to start Primo applications?

When you get consistent growing temperatures / applications can start as soon as consistent grass growth commences.

Primo Maxx


What rate should I go at?

It depends where your spraying. Rates vary for different grass types and heights of cut. But we would generally advise going half rate for the very first application of the season.

For greens for example:

Primo Maxx

The bottom line here is related to water rate. Primo wants to be available to the foliage and crown not the roots so we are targeting a foliar application. Ideally using a purple or red nozzles to get the right droplet size to leave that product on the leaf and avoid runoff.

It only needs an hour on the leaf before its rainfast, which works out well for UK & Ireland weather patterns, and allows it to fit in with irrigation cycles in the summer.

What benefits does it give?

There are many benefits to building a primo program. Its a product that’s popular here but also hugely popular in the US. Meaning we have literally decades of data to support its performance in a huge array of different areas.

In terms of performance benefits you can expect:

Where can I buy Primo Maxx


from vertical growth into lateral growth and rooting.

It sounds too simple, but a plant with a better established root system is better able to uptake nutrients and moisture.

When we are able to bring down clipping yields we leave the plant more of the leaf tissue it has painstakingly created, so it doesn’t need to replace what has been lost as urgently.

Something that we haven’t spoken about so much in the past are its benefits in terms of cost/labour saving, and savings in terms of CO2 emissions.

Primo Maxx


The figures quoted can be taken with a pinch of sugar (is that the opposite of salt?), since all the costs involved have gone up since the study was published, fuel and machinery increasing significantly in the last few years.

There really has never been a better time to use Primo Maxx II!

How long between sprays?

For any Matrix fans, this is very much the difference between the red and blue pills.

You can get fairly good results with the “blue pill”

Simple, classic:

  • Cool weather – every 4 weeks
  • Warm weather – every 2 weeks
  • In the middle – In the middle

But for those who wanted the red pill before I even listed it, its GDD for you.

GDD (Growing Degree Days) is a great tool to track grass growth. Its simply using temperature. The colder it is the less the grass will grow and the warmer the more growth.

It really just formalises what turf managers are feeling “Its warm today” but that doesn’t tell us if it stayed warm all day, or if it was warm at night etc. Its going to give you more accuracy than the first method especially at changeable times.

No system is perfect but with GDD you can get fairly close.

What are the downsides to using Primo Maxx II?

I’ve touch one one already, people have sometimes reported slight yellowing after the first application of the season, but this is generally negated if you include a little foliar nutrition with the spray.

It gets ‘hooky’. Not that many do, but its probably hard to come off primo once the benefits have kicked in. For most it becomes a solid part of the turf management strategy.

Here’s a younger Dan talking about Primo Maxx II in his own words.


Watch Video about Primo Maxx

This article first appeared in the Greencast Advisory Blog - you can read all the turf articles here.

Check availability and order Primo Maxx here.