Primo HG Lawn Growth Regulator

Mowing every few days in peak season and still falling behind?

Primo HG is a turf growth regulator. It slows leaf and stem growth so you mow less, and the lawn grows greener and denser. One 500ml bottle treats 1,250 to 5,000m2 on buffalo and couch, depending on the rate you use.

Fast summer growth means more mowing, more clippings and a lawn that looks scruffy a few days after every cut. Primo HG slows that growth down.

What it does

Primo HG contains 120g/L trinexapac-ethyl. It is absorbed through the leaf and reduces the elongation of stems, stolons and leaves above ground. The label rates are designed to give approximately a 20 to 50% reduction in clipping yield over 2 to 6 weeks. Growth regulation begins 3 to 5 days after application. Results vary with growing conditions and how the lawn is managed.

Which grass types

The label lists buffalo, common couch, hybrid couch (Greenlees Park, Santa Ana, Wintergreen), kikuyu, fescue, perennial ryegrass, carpet grass, bent grass and bahia grass. Do not apply to Kentucky bluegrass, as damage may occur. Zoysia is not listed on the label.

Application rate

Mix with water and spray over 100m2 using a backpack or garden sprayer. Each rate below is per 10L of water over 100m2.

• Buffalo, common couch and hybrid couch: 10 to 40ml. One 500ml bottle treats 1,250 to 5,000m2.
• Kikuyu: 20 to 80ml. One 500ml bottle treats 625 to 2,500m2.
• Fescue and perennial ryegrass: 20 to 60ml. One 500ml bottle treats about 830 to 2,500m2.
• Carpet grass, bent grass and bahia grass: 20 to 40ml. One 500ml bottle treats 1,250 to 2,500m2.
• Winter grass reduction in bent grass: 4 to 10ml.

Use the lower rate when growth is moderate. Use the higher rate when growth is vigorous or when you want 4 to 6 weeks of regulation. Repeat applications can be made as soon as the lawn resumes growth, or sooner if you need more suppression.

How to apply

1. Shake the bottle well.
2. Add half the water to your sprayer.
3. Add the Primo HG, then the rest of the water. Close the sprayer and shake.
4. Mix only what you will use that day.
5. Spray evenly over the leaf of the area you are treating. Primo HG works through the leaf, so coverage matters.

Apply when the lawn is actively growing, well maintained and getting regular water and fertiliser. Do not mow for 6 hours before or after application. Do not apply if rain is expected within 1 hour, and do not water for at least 1 hour after. Wash out your sprayer and measuring utensils with water onto the grass.

What to expect

Days 3 to 5: Growth regulation begins.
Weeks 2 to 6: The period the label rates are designed to cover, with approximately 20 to 50% less clipping yield. How long it lasts depends on the rate, grass type and conditions.
Ongoing: Apply again when the lawn resumes growth. Lower rates in spring, higher through summer, lower again into autumn.

When not to use it

Do not apply to lawns recovering from wear, renovation, disease, waterlogging or other stress, including lawns going into or coming out of dormancy. Do not use where growth regulatory effects are likely following a fungicide or any other product. Do not graze treated lawn or feed clippings from a treated area to poultry or livestock.

Complete the program

Primo HG slows growth, so it suits a healthy lawn, not a stressed one. The label says best results come on lawns that are actively growing, well maintained and getting regular water and fertiliser. The Turf and Surf program builds that foundation: soil first, then the leaf.

View the Starter Pack: Soak, Vital and Surge for $150

View the Full Routine Bundle: all 5 products for $244

Frequently asked questions

Will it stop my lawn growing altogether?
No. It slows growth. The label rates are designed for approximately a 20 to 50% reduction in clippings, not a stop. Use the lower rate if you are unsure.

Can I use it on zoysia?
Zoysia is not listed on the label, so we do not recommend Primo HG for zoysia lawns.

Can I use it on a new or recovering lawn?
No. The label says not to apply to lawns recovering from wear, renovation, disease, waterlogging or other stress.

Can I mix it with my Turf and Surf liquids?
The label gives no tank-mix guidance, so we recommend spraying Primo HG on its own, separate from your other products.

How many applications does a 500ml bottle give?
On a 100m2 buffalo or couch lawn at 20ml per 10L, one bottle gives 25 applications. On a 400m2 lawn at the same rate, it gives about 6. Kikuyu uses more per application, so a bottle goes about half as far.

Can I apply it before going away?
Yes. Because the label rates are designed to slow growth over 2 to 6 weeks, one application before a trip can mean less overgrowth when you return. The effect varies with conditions and rate.

What safety precautions do I need?
May irritate eyes and skin. Avoid contact with eyes and skin and wash your hands after use. Keep children and pets off the treated area until the spray has dried. Keep out of reach of children. Do not let the product or spray get into drains, sewers, streams or ponds. If poisoning occurs, contact a doctor or the Poisons Information Centre on 13 11 26.

How do I store it?
Store in the closed, original container in a cool, dry place out of direct sunlight and out of reach of children.

Always read the label before use. Not to be used for any purpose, or in any manner, contrary to the label.

View the complete 12-month Turf & Surf program guide