Excessive Rain = Weed Explosion. Here's How to Stay in Control

Your Guide to Post-Rain Garden Control

Heavy rain brings more than just soggy shoes and green lawns—it can trigger a weed explosion in your garden. The mix of moisture, warmth, and disturbed soil is the perfect storm for weeds to sprout and spread fast.

Here’s how to get on top of the outbreak—and keep your garden in control.

Why Rain = Weeds Everywhere

After a good soaking, weed seeds in your soil wake up quickly. Rain softens the ground, making it easier for weeds to push through—and easier for new seeds to take hold. Even worse, water runoff can carry weed seeds across your lawn or garden beds, creating new hotspots.

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Step One: Know Your Enemy

You can’t win a battle if you don’t know who you’re fighting. Start by identifying what’s growing.

• Broadleaf weeds like bindii, clover and dandelions usually invade lawns.
• Grassy weeds like crabgrass blend in and spread fast.
• Persistent invaders like Nutgrass are tougher and need more targeted control.

Different weeds need different approaches—so proper ID saves you time and money.

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Prevention is Your Best Defence

Stopping weeds before they take root is the easiest way to avoid a major cleanup later.

• Feed your soil, not your weeds
  Healthy soil grows strong plants that crowd out invaders. Add compost or organic matter, and check your soil pH—most garden favourites prefer a slightly acidic to neutral range (6.0–7.0).
• Water the plants, not the whole patch
  After rain, hold off on watering until your soil starts to dry out. When you do water, aim low—drip irrigation or soaker hoses deliver water right to the root zone, keeping surface soil drier and less inviting for weeds.
• Mulch like you mean it
  A thick layer of mulch (about 5–7cm) helps smother weeds by blocking light. It also holds in moisture and improves your soil over time.

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When Weeds Take Over: What to Do

If weeds have already popped up, act quickly before they seed and spread further.

• Pull them while the soil’s still soft
  Right after rain is the best time to pull weeds. The roots come up easier, which means less chance of them growing back.
• Use herbicide carefully
  For larger outbreaks or tough species, herbicides can be effective—but be selective. Spot-spray with a trigger bottle or wand to avoid harming your plants.
• Go organic if you prefer
  Vinegar-based sprays, boiling water, and corn gluten meal are good options for small patches or surfaces like driveways. Just note: organics often need repeat applications.

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Smart Use of Herbicides (and Why Timing Matters)

Not all herbicides are created equal—and when you apply them can make or break your results.

Pre-emergent herbicides: Stop weeds before they appear

These products create a barrier in the soil to stop seeds from sprouting. They’re ideal for lawns and garden beds where you want to prevent known troublemakers.

Top picks:

• Freehand – Great for wide coverage and controls both grassy and broadleaf weeds. Ideal for garden beds, turf, and around ornamentals.
• Barricade HG – Long-lasting protection. Apply it early in the season or after rain to stop a second flush of weeds.
• Dismiss – Handy if you want a more targeted pre-emergent, especially around existing plants and edges.

Tip: Reapply after heavy rain if your area is prone to runoff, as water can break down the herbicide layer or move it out of position.

Post-emergent herbicides: Tackle weeds that are already up

Use these on established weeds. Some kill everything they touch, others are more selective.

Top picks:

• Weedmaster Duo – Fast-acting and broad spectrum, but non-selective—so avoid spraying on plants you want to keep.
• Sempra – If Nutgrass is your problem, this is your go-to. It targets sedges without harming lawns.
• Dicamba M – Safe for most turf types (excluding Buffalo) and excellent for removing bindii, clover, and other broadleaf weeds.
• Buffalo Bindii & Broadleaf Weedkiller – Specially made for Buffalo lawns. Gentle where needed, tough where it counts.
• Crabgrass & Clover Killer – Targeted control for two of the most common post-rain pests.
• Slasher – A natural, fast-acting, non-selective herbicide that burns weeds on contact. Great for paths or eco-conscious gardeners.

Make it stick: Use a surfactant

Add Wetter 600 to your spray mix to help herbicides stick better to leaves—especially important after rain when plants are waxy or dusty. It improves absorption and reduces waste.

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Eco-Conscious? You’ve Got Options

Weed control doesn’t have to mean drenching your garden in chemicals. These alternatives are worth a look:

• Manual removal – Still one of the best methods when done right. Moist soil helps you get the full root.
• Soil solarisation – Cover a patch of weedy soil with clear plastic for 4–6 weeks in hot weather. The heat kills seeds before they germinate.
• Plant cover crops – Clover or vetch in unused areas can block weeds and improve your soil at the same time.
• Mow higher – Keeping your lawn longer shades out weed seedlings and reduces bare spots where weeds can take hold.
• Boost biodiversity – Healthy, diverse gardens with native plants outcompete weeds and support helpful insects that keep your ecosystem in balance.

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Stay One Step Ahead: Make Weed Control Routine

Weeds thrive when you're not looking—so make regular check-ins part of your routine. Here’s how:

• Weekly garden walks
  Take 5–10 minutes each week to walk through your garden. Spot new weeds early, check for areas holding water, and look for gaps where weeds might sneak in.
• Keep tools handy
  A weeding knife or small hoe kept near your garden beds makes it easy to deal with problem spots on the go.
• Stay seasonal
  Plan your weed control around the weather. Pre-emergents in early spring and after big downpours, post-emergents when weeds are actively growing—and always before they seed.

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Reclaim Your Garden (and Keep It That Way)

After heavy rain, a weed outbreak can feel overwhelming. But with the right approach—and a bit of consistency—you can turn it around fast.

• Start with prevention: healthy soil, smart watering, and thick mulch.
• Tackle active weeds quickly with the right tools or herbicides for the job.
• Use eco-friendly methods where you can, and keep an eye out regularly.

With a little planning and some garden know-how, you’ll stay in control—rain or shine.

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Need a Hand Choosing the Right Weedkiller?

Our team’s here to help. Get in touch or visit the Weed Control section of our store to browse our full range of solutions—pre-emergent, post-emergent, organic, and lawn-specific.

Let’s grow!