My daughter has a real messy area in her garden. She would like to use round-up and then replant at a later date. She does have a large number of tulip bulbs that are planted at least 6 inches deep. Will the round-up kill the bulbs?
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.
Herbicides are very different in their properties. Roundup will tightly adhere to soil particles where it will biodegrade completely over time. It is not a herbicide that has shown tendencies to travel into water tables, nor will it travel down to dormant tulip bulbs and cause problems. That being said, long term control of weeds in this situation is best achieved by consistant removal of weeds, and application of a good weed suppressing mulch. Roundup can be useful to control deep rooted perennial weeds that are difficult to hand pull effectively.
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!
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.