In order to prevent weeds from overtaking your iris beds, apply a pre-emergent in spring to prevent weeds from sprouting. Then, use an iris-safe weed killer spray on weeds that do appear.
To keep weeds out of irises without chemicals, hand pull existing weeds or dig up iris rhizomes to remove weeds that are tangled with your iris roots. Then, spread mulch around your irises without covering the rhizomes and build a border around your garden to control invasive grasses.
6 Methods for Preventing Weeds in Iris Beds
The following methods will help your reclaim even the most weed-infested iris bed and keep weeds out permanently. This can be accomplished with EPA-approved herbicides, or with an all-natural approach. Either way you go, you can keep your irises blooming beautifully and free of invasive weeds.
Apply Pre-Emergent in Spring
Once soil temperatures rise to 55℉ (13℃) in spring, apply an iris-safe pre-emergent herbicide. Preen is safe for use in iris beds. It will kill weeds, grass, and other plant seeds as they sprout underground, but won’t harm your iris rhizomes.
Keep in mind, Preen and other iris-safe pre-emergents won’t kill existing weeds. Pre-emergent herbicides attack seeds as they germinate but won’t harm existing plants and roots. A single application of pre-emergent in spring will keep new weeds from sprouting in your iris beds through the flowering season.
If you have pesky annual winter weeds that invade your iris beds, perform a second pre-emergent application in fall, typically between September and October.
Use a Weed Killer Spray that Won’t Harm Irises
If you have an abundance of weeds currently taking over your irises, use this weed killer that won’t harm irises. Weed and grass roots commonly tangle with iris roots, making it difficult to hand weed without uprooting your flowers. A weed killer containing sethoxydim attacks invasive weeds but won’t damage your irises and other garden plants.
If you want to get rid of existing weeds naturally, the best way is by hand-pulling. It’s the only non-chemical method that kills weeds down to the root. With this weeding tool, the job is a lot easier.
- Avoid homemade weed killers that contain vinegar, salt, or soap. These won’t kill weeds down to the root, only slow them down.
- Vinegar-based weed killers harm irises on contact, damaging leaves and blooms.
As mentioned above, the roots of weeds and pest grasses commonly tangle with the roots and rhizomes of your irises. If your hand-pulling efforts are disturbing or damaging your iris plants use the next method for weed control.
The Dig-and-Trim Method
How do you get weeds out by the root without damaging your iris rhizomes? Often, the roots of weeds and rhizomes are tangled together. The good news is, iris rhizomes are extremely resilient, so the following method works wonders:
- Dig up iris rhizomes in late summer or fall.
- Wash the dirt from the rhizomes.
- Cut rhizomes into 3-inch sections so that each contains a leaf fan.
- Disentangle and dispose of any weeds and weed roots that have wrapped around the rhizomes.
- Remove the weeds from the iris bed while the rhizomes are out of the soil.
- Replant the rhizomes, making sure the top of the rhizome is just above the soil surface.
Not only is this a great way to get rid of weeds without any fear of harming your flowers, irises actually benefit from being divided in this manner once every 3 years.
Mulch Your Iris Beds Carefully
In spring, lay mulch in your iris bed to control weeds. In order to do this correctly, follow these guidelines:
- Lay 3–4 inches of the mulch of your choice (bark mulch, shredded leaves, nut husks, pea gravel, etc.) in your iris bed.
- Mulch around the iris rhizomes but do not cover them with mulch. Irises buried in mulch are subject to rot.
Mulch works as a natural barrier that keeps weeds from receiving sunlight, killing them as they try to sprout. Not only that, but mulch invites crickets, which eat weed and grass seeds but won’t harm your irises.
Build a Garden Border
If grass is spreading from your lawn into your iris bed, it’s time to build a garden border. Use stones, bricks, or this flexible wood border to create an attractive boundary. This will not only keep your weed-suppressing mulch in your iris bed, but it will also control grass. Spreading grass runners are unlikely to crawl over a garden border to invade your irises.
Does Roundup Kill Irises?
Roundup is deadly to irises, as well as any other plant or grass it comes in contact with. Never spray Roundup or any other Glyphosate on irises or your plants will be killed down to the root.
When spraying for weeds in iris beds, use only products that contain sethoxydim as the active ingredient, such as this weed killer. Other herbicides will harm your iris plants.
How to Prevent Weeds from Growing in Iris Beds
If you want to get rid of weeds in irises and keep them out, use these methods:
- Spread pre-emergent in your iris bed in spring, to stop weeds from sprouting.
- Spray existing weeds with a sethoxydim-based weed killer to destroy weeds without damaging irises.
- Hand pull weeds to remove them naturally.
- Dig up iris rhizomes in the fall, weed the bed, then trim and replant the rhizomes.
- In spring, mulch your iris bed, making sure not to cover the rhizomes.
- Construct a border around your garden to control grass and keep it from spreading into iris beds.
Use one or all of these methods together to destroy existing weeds in your irises and keep them from returning. With a little work and the right tools, you will be able to enjoy your irises without the threat of weeds.