Is It Safe to Use Pre-Emergent Weed Preventers Around Bulbs? - Today's Homeowner (2024)

FAQs

Does weed killer affect bulbs? ›

Use caution when spraying weed killer in beds with bulbs that have died back. Many bulbs, even when dormant, react to weed killer that seeps into the neck of the bulb.

Pre-emergent weed control is not harmful to your lawn. If you plan to plant new seeds for ornamental plants to compliment your landscape, or new grass seed to your lawn, treatment should not be applied to those areas prior to germination.

Pre-emergent herbicides are a great way to cut down on the amount of many annual and perennial weed seeds in flower beds. Pre-emergent herbicides control a variety of weeds but not all weeds.

Pendimethalin is a man-made chemical that is used as an herbicide, primarily as a pre-emergent. It is effective for treating grassy weeds. The Environmental Protection Agency rates this chemical as having a low toxicity rate.

Trifluralin, the active ingredient in Preen Garden Weed Preventer, is also listed as safe around bulbs. On the other hand, Preen Lawn Crabgrass Preventer, isn't recommended for use around bulbs.

A bulb is a combination of a nutrient storage area and the start of a yearly flowering plant. Most bulbs must be planted several inches below the soil surface in order to produce strong growth. Weed blocker, or landscape fabric, that covers bulbs hinders their sprouts and causes failed growth.

Early Spring and Fall are the most effective times to apply pre-emergent herbicides. They can be applied throughout the year, and will still prevent new weeds that sprout, however most weeds sprout during spring and fall.

We recommend considering a pre-emergent application in the late winter to early spring to maximize its effectiveness. Every pre-emergent product is a bit different, but you can expect a single treatment to last approximately 3-5 months.

If you would like to prevent spring weeds in the lawn, purchase pre-emergent and get it ready to go for when conditions are right – usually around mid-February to early March. Pre-emergent is recommended for lawns twice a year.

What happens if you put down pre-emergent too early? ›

If applied too early, preemergent herbicides can get washed away by rain or be washed too deeply into the soil, rendering them ineffective. If applied too late, their enzymes don't properly work, and the weeds will grow up anyway. That's why it's important to watch the temperature and know exactly when to apply them.

Insecticides & Herbicides

The International Agency for Research on Cancer classifies malathion and diazinon as probably carcinogenic to humans and dichlorvos, parathion, and tetrachlorvinphos as possibly carcinogenic to humans.

Glyphosate is relatively inexpensive – compared to other herbicides. And, it is considered to be one of the least toxic and environmentally benign herbicides in use.

Breaking the Barrier

Dimension pre-emergent crabgrass preventer creates a barrier on the surface of your soil, preventing germination from taking place. The best way to counter this barrier, is to "break it" by chopping up the soil, and overturning the soil.

As you plant your bulbs, using an organic mulch such as pine needles, pine bark or another shredded bark may help reduce the chance of weed problems when the bulbs emerge. Use 2 to 4 inches of mulch for your best chance at preventing weeds from growing.

The Gardener's Answer. Hello, Lewis in Virginia: Preen makes a lot of different products, but all of them are safe to use around bulbs as long as the bulbs are buried 3-4 inches deep in the soil.

Many gardeners can even get put off from planting bulbs at all, as they're so used to never seeing the fruits of their labor. In actual fact, squirrels are most likely to be digging because they think freshly dug earth means a stash of nuts has been buried.

The easiest way to prevent weeds from being an issue is to spread 2 to 3 inches of mulch over the soil. Your bulbs will easily push up through it, but most weed seeds won't.

If it's a good membrane, then no, bulbs won't come up through it. If you want those bulbs up then cut a cross in the membrane and let them through. You might get a few weeds coming through but a lot easier to deal with than the whole bed.

What do you put down to stop weeds coming through? ›

Mulch Your Beds

An effective and natural option to prevent weeds from taking over your garden is through the use of mulch. Apply a thick layer of organic mulch approximately 2 inches deep in the garden area – take care to avoid the base of individual plants and shrubs.

Preemergence weed control applications eliminate invasive plants before they begin to grow. Different weeds sprout and spread at different temperatures. Hence, it's never too late for preemptive treatments to work in your favor.

When it comes to pre-emergent weed control timing is everything, especially when using herbicides like LESCO's Dimension to control summer annual weeds. Rule of thumb is to get the application down before the soil temperatures are 50-55 degrees for five or more consecutive days.

Apply pre-emergent herbicides between February 15th and March 1st to kill spring weeds before you even see them sprouting. Any later than that window, and it's probably too late to kill weeds with a pre-emergent herbicide (you'll need to switch to a post-emergent to apply directly to the weeds).

How will rain affect the pre-emergent that was applied to my lawn? That's a good question. A lot of people think rain will wash away our products and make them ineffective, but this is simply not true. Actually, rain makes our lawn treatments work much better.

Principle #3: Pre-emergent herbicide must be watered in.

Watering in activates the herbicide, creating a barrier just below the surface. Most products call for 0.5 inches of irrigation or rain within 21 days after application.

Many pre-emergent products will allow you to make heavier product applications to get more extended control. I like to apply at a heavier rate in late January so the product will last through March and prevent crabgrass seeds from germinating.

Early spring and fall are the most effective times to apply pre-emergent herbicides. Applying a pre-emergent herbicide will prevent seeds from sprouting, but the most effective times to use it are in the spring and again in the fall.

Winter weeds. Who knew there were two completely different weed seasons? Yet, two seasons there are – which is why gardeners-in-the-know apply Preen at both times of year: in spring to stop summer annual weeds, that germinate in spring and summer, and in early fall to stop winter annual weeds that sprout in fall.

The class of weed control products known as pre-emergents are highly effective herbicides if used properly. They are relatively simple to apply and can save a lot of headache later in the season if care is taken to apply them properly. Sometimes though, weeds will grow even after you've applied pre-emergents.

Can you apply pre-emergent in the spring? ›

Pre-emergents should be applied at least twice a year. As previously mentioned, they should be applied in the spring before the ground temperature reaches 55 degrees Fahrenheit. Then it should be applied again in the early fall after temperatures begin to come down.

Apply in early spring to prevent the germination of crabgrass, chickweed, poa annua, and other common lawn weeds, before they start to spread.

Grubbs-Bowling says pre-emergent weed preventers are best suited for grassy weeds and annual weeds that reproduce by seeds. “They don't work as well on perennials.” Annual weeds are either winter annuals or summer annuals.

An excessive application may also prevent the proper establishment of grass seed later in the season.” Meanwhile, skipping an application of pre-emergents entirely, for whatever reason, can end in crabgrass or other weeds dominating a lawn by the end of the summer.

Since pre-emergent herbicide must be washed into the soil to be effective, you can mow before applying it, however you should wait a few days after application to mow again.

If used too early, it can break down before the seeds germinate. If used too late, a full-blown infestation could already be underway. Pay close attention to the soil temperature and try to apply a crabgrass preventer right before it's forecasted to rain, if possible.

Using Bleach to Kill Weeds Permanently

Apply one cup of bleach, undiluted, to the afflicted area. Wait until the weeds turn brown before pulling them out of the ground. Run water around the area to flush the bleach, especially if you are trying to grow plants or grass in that area.

Mulch After Weeding

Stay one step ahead by filling in the bare spots with more flowers, or by spreading two inches of mulch over the entire bed. That's usually enough to smother any new weeds that try to sprout. To prevent rot, keep the mulch at least a couple of inches away from the stems of your flowering plants.

Yes, vinegar does kill weeds permanently and is a viable alternative to synthetic chemicals. Distilled, white, and malt vinegar all work well to stop weed growth.

Glyphosate is among the safest herbicides in use today. It inhibits an enzyme in plants (but not animals), it decomposes rapidly in soil, and if consumed it largely passes through the body.

How do herbicides effect human health? ›

Examples of acute health effects include stinging eyes, rashes, blisters, blindness, nausea, dizziness, diarrhea and death. Examples of known chronic effects are cancers, birth defects, reproductive harm, immunotoxicity, neurological and developmental toxicity, and disruption of the endocrine system.

If you're exposed, your eyes, skin, nose, and throat may get irritated. If you get it in your eyes, it could lead to mild irritation or a superficial corneal injury. If you swallow it, you may have increased saliva and burns and pain in your mouth and throat. It can cause nausea, vomiting, and diarrhea.

Spraying a little white vinegar onto the leaves of weeds can keep them under control as well. Grocery store vinegar will do, but more acidic vinegar is also available at your local home and garden store. You can also combine a little rock salt with the white vinegar for added weed-killing power.

Originally used as a supplement in hog feed, corn gluten has become a common organic alternative to synthetic chemical herbicides. It can be effective as a pre-emergent herbicide used to control crabgrass and other lawn weeds, and it also has nutritional properties.

How Long Does Pre-Emergent Weed Control Last? ‍Every product is a bit different. Typically, you can expect one treatment to last 3-5 months. However, Canopy recommends applying a split application approximately one month apart to maximize effectiveness.

Using Acetic Acid as a Herbicide

Vinegar is not labeled for use as a pesticide, so Cooperative Extension agents aren't able to recommend its use. But a homeowner can experiment. Household vinegar works well on young weeds. Repeated applications improve its effectiveness.

How much should I water after pre-emergent? If you have a lawn sprinkler system – for rotor head areas, 15-20 minutes per watering event is good, and 4-6 minutes per event for spray-type heads. If you're using a hose and sprinkler, you're probably going to be closer to 20 minutes per area.

Roundup doesn't leach through the soil, so it won't hurt the bulbs if there are no living leaves above ground to absorb it.

As you plant your bulbs, using an organic mulch such as pine needles, pine bark or another shredded bark may help reduce the chance of weed problems when the bulbs emerge. Use 2 to 4 inches of mulch for your best chance at preventing weeds from growing.

The first thing you will have to do when trying to remove bulbs from garden areas is to put a black plastic covering over the bulbs during growing season. This will block out all the sunlight and will prevent bulbs from growing. In the fall, dig out the unwanted bulbs.

How do you keep weeds out of tulips? ›

Mulch. Mulch naturally suppresses the growth of most annual weeds by blocking out light and limiting exposed soil surfaces. Popular mulch material include bark chips, straw and wood chips. For enhanced weed suppression and prevention, lay landscaping fabric on top of your flower bed's soil before layering on the mulch.

Glyphosate binds tightly to soil. It can persist in soil for up to 6 months depending on the climate and the type of soil it is in. Glyphosate is broken down by bacteria in the soil. Glyphosate is not likely to get into groundwater because it binds tightly to soil.

1 Day After Application: Ornamental flowers, trees, and shrubs. 3 Days After Application: Lawn grasses, herbs, vegetables, and fruits.

According to Robert Kremer, phosphorus-rich soil can result in glyphosate teaching into the groundwater and contaminating it. Roundup is also believed to poison the helpful microorganisms in the soil. Kremer said the glyphosate leaches into the plants through the roots.

Mulch is an effective weed suppressant, but it should be applied after the landscaping bed is treated with a pre-emergent herbicide to reduce the likelihood of weeds appearing at the soil line.

Just soak the clump heavily with water, pull slowly at the base and all the bulbs in the clump should pop right out. If the roots don't come out, you didn't soak the area well enough and/or placed your hands too high. Once a clump is removed, it will not grow back.

Problems with mulching occur usually when you've mulched too thickly, which prevents bulbs and herbaceous plants from growing.

If the soil and air temperatures are above average for an extended period of time, leaf and flower buds may sprout ahead of schedule. Installing bulbs too shallow is another reason for bulbs sprouting in winter. The rule of thumb is to plant bulbs at a depth that is three times their size.

Most bulbs can be left underground all year or stored inside after they've bloomed. After your bulbs have flowered, don't remove their leaves while they're still green; always let the foliage die back on its own. Bulbs gain their strength from their foliage, helping them grow and produce new flowers next year.

The trick to ensuring bulbs are safe and happy all winter long is to keep them uniformly cool. So after you plant, it's valuable to put mulch on top of the soil. Not only does mulch keep the bulbs uniformly cool, but it also inhibits weed seeds by cutting off the light that encourages germination.

Can you use vinegar on weeds? ›

Yes, it's true… vinegar does kill weeds, especially when used along with dish soap. Dish soap, vinegar and a spray bottle are all you need for making your own weed killer. The acetic acid in vinegar “sucks out the water” from the weed, which dries it up.

The 'Bulbing' Weeds: Wild Onion, Wild Garlic and Star of Bethlehem.