Roundup doesn't travel through the soil. It affects plants when it is applied to the plant's growing tissues (leaves, stems).

According to numerous [world-wide] scientific studies, the ingredients contained within most herbicides DO remain in the soil, as well as percolating into the water table. There have been many, many, many prior discussions about the research which shows the lasting aspects.

If directions are followed carefully, the herbicide *may* cause the plant/s to die as it is absorbed by the living tissue. Read the label carefully, and note that most herbicides suggest best effectiveness when used on new/growing leaves. Unfortunately, most commercial chemical herbicides require repeat applications to be effective, which increases your exposure to the chemicals both now and later.

You don't say *what* plants are causing the mess, but the most effective [and permanent] way to clear the area of *any* weed is to hand-pull the weeds immediately after the soil is soaked to a depth of at least 4 inches; and then put a 3" mulch over the bare soil.

If that is too much effort, then one can use the lasagna method with the bottom-most layer being about 1/2" of sopping newspaper; then alternate 1" layers of green and brown organic materials to a depth of 8" to 18", and finish by topping off with 2" organic mulch. That is sufficient to suffocate practically all weeds (heavy briars require a base of 1" wet paper), but the lasagna will have decomposed enough by next spring to not affect the bulbs. The additional benefit of the lasagna method is that the soil is improved.

If lasagna is also too much work, then pour near-to-boiling water over the weeds, or carefully use a flamer. With any of these methods you can feel sure that you have not contributed to worsening Earth's quality.

I, and many others on these forums, can attest to the effectiveness of newspaper and/or cardboard under mulch to effectively smother weeds. By the time the tulips are ready to come up again it will have rotted and pose no obstacle.

That said, RoundUp won't affect the bulbs as long as there is no green portion above ground when it is sprayed.

To condense and summarize, if all the green on the tulips is out of the bed, round up will kill the weeds without hurting the bulbs....I know, I have sprayed Round up over the top of sleeping bulbs many times without hurting what lies beneath.
I would not be laying layers of newspaper over my tulips. A lottle Round up and then a mulch would be best.
I don't use chemical fertilizers....I don't spray routinely with fungicides nor insecticides, and I use no herbicides but Round up and a week digging knife!
Linda C

What if the bulb has sprouted and has leaves/greenery above the ground...will spraying Roundup on the leaves kill the bulb?

I have the same situation...I moved to a new house where the previous owner literally planted hundreds of bulbs. I would like to start over with a simpler garden.

That's such an expensive & iffy way to get rid of tulips.

To be sure you have them all out & to make the garden soil as hospitable as possible for your new plants, you need to till or turn the soil anyway.

Tulip bulbs are pretty big:
If there's one in there, turning the soil will turn it up.

If this were my garden, & I didn't want or wasn't able to turn up the soil myself, I'd advertise free bulbs for the digging on freecycle.

I second Sylvia's motion to post them on FreeCycle. That way someone who wants them can come dig them up for you and they'll also be providing free labor in turning over the area for you to plant whatever you plan to plant. If you're not sure what the bulbs are, just say so, there are still lots of people who would be glad to come dig free bulbs.

I have posted "Free Bulbs" many times and always get a good response. I do go back into the areas after to look for more invasive bulbs because salvagers are not interested in being thorough. I never let them do it unsupervised.

I know this a old post but As some others have said - Roundup doesn’t have any soil activity. It requires green i.e., chlorophyll and temperatures above 50 to work. It seems you are writing this in June — personally I would wait another month unless you are positive the bulbs were say March or early April bloomers and have completely dried up. Many tulips bloom in May and all bulbs need to die down naturally or you risk the bulbs getting smaller each year which tulips will do anyway unless a perennial type. The bulbs get “food” by photosynthesis and need the sun until the leaves are totally dried up and back below the surface. A little bulb food or bone meal helps too. If there is still yellowish turgid pieces sticking up the roundup can seep into living tissue. It normally takes a couple of months after flowering and you don’t want to cut them off - the best you can do is braid the foliage and we did it for years - don’t laugh. But if you mark them - use a non toxic marking paint and spray a circle around each clump about 6-8” out from the base in all directions. The reason for the circle, is after you spray the weeds, you will 1) know where to not spray just in case but better is to plant in between a groundcover, or other plants like daylilies or whatever perennial for the location (sun or shade) that will fill in between the bulbs (tulips, daffodils, whatever) so the dying foliage isn’t noticeable and can die naturally but more importantly shade out weeds. The circle is to prevent digging up bulbs or damaging vital roots. You can use Preen (there are several varieties for the right situation (go to their Preen website) in and around your plantings several times a year to catch whatever weed seeds there are and keep them from germinating. Just remember no matter what you spray or use there are always more weed seeds. Even after mulching - birds drop weed seeds, and the wind blows the seed in. So using something like Preen (a pre emergent though they might have a post) several times a year is best. The next best is roundup on areas with no plantings (flowers,ground covers, trees, shrubs, lawn) — just bare ground covered with weeds. There are weed killers for broadleaf weeds and for grassy weeds and you must determine what you have in order to choose the right one. Honestly, most of us have both. I don’t care for post and pre emergent herbicides because they hang around too long and stop you from being able to plant anything else (seeds or plants) plus most kill clover and the little purple native violets. But it’s their soil presence that bothers me. Roundup may sometimes bind with the soil but it’s not doing anything - its just sitting there until it breaks down. I’m very distressed the Roundup gets the bad name because of one actual heard case (as far as I can tell). And it was well studied environmentally but the court case that was won was based on a “new study” however they didn’t run any new tests, they cherry picked a few cases out of the old study and reworked the data. All of this data is available to anyone who chooses to look at facts and not a bunch of hysteria from those who like to cause trouble and make money. Mostly that’s the lawyers who profit greatly at 20-30% of every case. Yes, we don’t want to be stupid —like any chemical they are all dangerous, so is the bleach, and cleaning products in your house and garage. Gas you put in your car, and insecticides we use on our animals to relieve tormenting flies and ticks - all chemicals have some detrimental effect if used wrong. Even vinegar if used higher than what you mix for salads and cooking. Horticultural vinegar is 20% and very corrosive and acidic. I have used Roundup for around 20 years and it has always advised protective equipment (long sleeves and full pants, gloves, mask that doesn’t allow penetration, and eye). To me anyone who gets cancer either can’t read or stupidly chooses to not read and follow full directions. Don’t blame the chemical company, they they have been telling us for 50+ years these are dangerous chemicals. Always, prior to buying any chemical go to the manufacturers website (not the seller or third party — most times I find, after 50+ years of gardening, they don’t know much more than you do. But read all about the product and the mfg tips and even other products they might have and then read the government required MSDS or SDS (safety data sheet) (M stands for Manufacturer’s) for the active ingredients and all safety and environmental issues. This way you will know what it might harm or where you shouldn’t use or dispose of the product. This goes for herbicides, cosmetics, laundry products — everything thst has some form of a chemical as deemed one by the government. For example if it’s highly toxic to aquatic life, don’t let it get to any body of water but also not into sewers or your household drains because that ends up in the local river, bay, swamps, etc. other ingredients are bad for not only fish, frigs, etc but for wildlife and pets to get to. Roundup, over all other herbicides, is about the safest we have in terms of no residential activity in the soil. And no matter what, never use chemicals near a groundwater source, i.e., wells and springs. That doesn’t mean you want to just spray/dump it willy nilly everywhere. Always go to the manufacturers website to get their full directions and tips for use and to see which product is best. They may have one that works better. Once you have the names of the active ingredients, look them up in reputable university or gov’t websites to see the possible damage — particularly to beneficial bugs and pollinators but certainly to us and other animals, water and air. They are in trouble. In lawns or around ornamental beds - there are better herbicides to use. And don’t forget to carefully read the MSDS/SDS sheets and label. Quite truthfully if you don’t fully understand how these chemicals work, the damage they can cause, it is best to talk to a company who is trained to do so and ask lots of questions. If something doesn’t jive, don’t use them — remember they are just trying to sell you a service - some are very good and conscientious— others not so much. I try to stay away from chain franchises and try to use local family operated service companies. And always make sure they will replace (full size) any plant they damage, stress, or kill along with the labor to do so. Always take pictures of your lawn, garden, and closeups of valuable plants before they spray the first time. Many of the chemicals that we now freely buy and use are really rated for professional use only. You will most times see it marked on the bag “professional use only” or will find the notation on the mfg website. That said, due to it being for professional use only and not suppose to be sold for individual homeowner use - many times the bags themselves might possibly not be marked but I believe most are. Many times bulk products (any type) are packaged more plainly and they assume only trained, certified individuals are buying and using them. However, due to the government having so much other stuff on their plates these days - enforcing who sells and uses what chemicals is not easy. They can work on catching big dumpers of chemicals but who is buying and selling what isn’t possible and would do what most people don’t want - become “bigger” govt. They need to crack down on the distributors, the “DIY pesticides, herbicides,fungicides, etc” retail stores, so they don’t keep sell these pro only products that are very dangerous unless you are trained. Part of the issue too is of price and gouging — if crooked pest and lawn companies only have access — they can charge us whatever and we can’t afford to do anything but go along with it. There are issues in the industry and we have to consider all of these. You can easily go get the training and be certified as a private applicator (your property only” or get commercial application. Here is the link from Maryland university for that state to give you an idea. Check for your own state. http://pesticide.umd.edu/certified-applicator-training.html.
In fact many of these chemicals travel via USPS who has laws against most of being shipped but yet it’s shipped all the time - so we can only blame ourselves on the issues created. IF - you are someone who checks out chemicals prior to buying and after purchase reads directions twice when first using and reads again at each use AND follows those directions— then I applaud you. You will keep us all and the environment safe for future generations. One thing I haven’t mentioned and it’s how our grandparents and their grandparents got rid of weeds — old fashion hard work with a hoe or hoe-fork. Maybe a sythe for brushy fields. Up until about WWII, there weren’t that many chemicals available to everyday folks and until about 1980s, there weren’t all these weed eaters and pressure washers. I’d like to see us go back to those days — it was safer, and certainly quieter. Gosh it wasn’t until the mid to late 50s and really into the 60s that home use gas powered push mowers came into large use. I remember reel mowers still being used into the 70s but then the mowers we know today exploded into use everywhere. The point being - we kept our homes clean with plain soap, water, bucket and brush (even long handled ones) and we didn’t tear up wood, causing more algae and mildew, nor void siding, and window warranties or tear the stones out of aggregate walks and drives. We kept the weeds and grass in check with quiet reel mowers that did a much nice job on the grass and kept it healthier due to the type of cut and neighborhoods didn’t sound like a dull roar or smell like gas and oil every evening or weekend. Neither did it have the whine and smell of weed wackers. Big sharp sythes kept big fields clean of weeds and grass in good shape with no need for expensive mowers and tractors. Large properties used horse drawn equipment and then later on steam boiler engines. I can’t wait until the day it’s all electric or we go back to some of the old equipment so I can enjoy my ice tea on the porch in evenings. We won’t go back to horses, most likely, but electric solar powered mowers or muscle pushed reel mowers and hand held grass trimmers for beds and long handled narrow spades for properly edged beds would be nice. Even brick edges the way we use to always due them worked great — well until they introduced Bermuda grass (wire grass). There are so many things we use to do and we stayed in better health and shape and didn’t go broke trying to buy all this equipment and chemicals. We are being held over a barrel and being bankrupted and we don’t seem to care. All that money could be saved for hard items things we will still have decades and decades later and not not spent on a weed killer that has to be sprayed at a minimum several times a year or used up in one use and re-applied and purchased constantly month after month, year after year. Think smart and long term and about those to come after us.