Questions & Answers

This page contains questions (edited) we have received from our viewers along with our responses.  
We thought you might find this information helpful.     


   How do I control weeds and grass around and between my Swedish aspens?  L., Alberta, Canada; 9/8/11

A:    After clearing the weeds you can spread Preen to prevent weed seeds from growing. Herbicides that kill only grass can be used. Don't use herbicides for broadleaf weeds or Roundup. They will kill the trees.

   After pulling all weeds with roots from sloping ground covered with stones (1" and fines), what is the best way to keep weeds from returning?  R. K. S., St. Louis County, MO; 8/13/11

   There are products, such as Preen, that can be scattered over the area to control weeds. Weed seeds in the soil will continue to germinate. Preen prevents them from growing.

   I want to get rid of the weed thyme that keeps creeping over to my lawn from a neighbors.  Roundup works but it kills everything and the weed keeps coming back.  I have also tried pulling out the weed but eventually when I plant new grass the weed once again cones back.  Can you help?  J. K., Lake Luzerne, NY; 8/11/11

   Thyme is a broadleaf plant. There are weed killers made specifically for lawns that kill broadleaf weeds in them and can limit the re-emergence of weeds.
Q:    Is crabgrass a significant problem in areas around and east of Denver and Colorado Springs?  R. K., Warrenton, VA; 7/7/09
   Yes, crabgrass can be a significant problem in Denver, Colorado Springs and areas to the east.  Places in Colorado below an elevation of 6500 feet can have problems with it.
Q:    I live in Massachusetts. Currently it's about 80 degrees out. I just bought a house that's been empty for over 2 years and the weeds around the back yard are taller than me!!!!! I've tried cutting them in half then pulling them out of the ground but we are talking about 1/4 acre worth. There is no grass under them...just soil.  I'd like to plant grass for next year. Is there an easier way to get rid of all the weeds without pulling each one out of the ground by hand? Some of the roots are up to 3 feet long? PLEASE HELP.  M. A., Blackstone, MA; 9/4/07
   In some ways you are lucky there is no grass growing along with the weeds.  That allows you to kill/clear the weeds without having to protect the grass.  I suggest that you spray the weeds with Roundup.  It kills plants, including the roots.  Protect any plants you don't want killed from the spray.  You can rake the dead weeds and prepare the soil for sod or seed in about two weeks after the application of herbicide.
Q:    We live in Debeque, CO, and we have those horrible weeds that produce goatheads.  No matter what we do they don't go away.  We have tried tilling, pulling and weed killers. On top of it all they still keep coming back.  Please help!  A., Debeque, 7/2/07
A: The reason the puncture vine (goathead) keeps coming back is there are seeds buried in the soil that germinate.  Using a pre-emergent weed killer for broadleaf weeds in early spring may help.  Roundup will kill plants that have sprouted.  Note: It will also kill the lawn and desired plants too if any gets on them.  It is vital that you kill the plants before they produce seeds.  It may take a while to get this weed under control.  For more information please see
Q:    Hi.  I have a front yard that is currently all dirt & weeds.  We are planning to xeriscape the area.  What is the best way to get rid of all the existing weeds when we do?  Also, I have an organic garden in back (we just bought the house) that is also FULL of weeds ( I didn't realize they could grow so quickly).  What is the best way to get rid of the weeds & keep them gone -organically - before I plant?  Can I just use a rototiller to re-do the soil or do I really have to pull them all up?  ~ New to gardening in Lakewood, CO.  I. T., Lakewood, 4/19/05
    To get rid of weeds in your front yard you may want to spray them with Roundup.  This herbicide kills all plants, so don't let it drift onto plants or lawn that you want to keep.
    There is no easy way to get rid of weeds organically.  You will probably need to hoe or pull them up.   A tip: it is easier to pull weeds when the soil is slightly moist.  Before you plant the garden, prepare the soil for planting and water it.  Allow it to sit unplanted for a couple of weeks so weed seeds can germinate and be cleared before you plant.  Another method to use it to cover the soil with heavy plastic for 1 - 2 months to solarize it.  This can kill diseases, insects and some seeds.  Using mulch also cuts down on weeds.  You can use a rototiller to get rid of the weeds, but that potentially may create more of them in the long run.  Rototilling will bring up weed seeds buried in the soil and it chops up roots into multiple pieces, some of which can sprout. 
Q:   Hi, I live in Pine Brook Hills area and my yard is full of spurge aka myrtle spurge or donkeytail spurge.  I am pulling them out but don't know if this the best thing I can do to get rid of them.  Is there a better and more efficient way?  Also, what is the best way to get rid of Canadian thistles?  I am cutting the root about 1 inch below the surface using a dandelion digger and people tell me that's not effective.  I had someone spray the thistles last year but they popped again this year.  Thank you.  D. M., Boulder, 4/14/05
   To get rid of myrtle spurge you can dig up mature plants, being careful to get the roots, and you can pull up new seedlings.  It is  easier to do weeding when the soil is slightly moist.  You can also kill plants by spraying them with Roundup.  This is an herbicide that kills any plant that the spray drifts onto.  If you have plants near the myrtle spurge that you don't want killed, you can dab Roundup on the weeds with a small paint brush.  Be sure to wear gloves and long sleeves when handling this plant.  You want to avoid getting the sap on your skin.  It is toxic and can burn the skin.
     Canada thistle is difficult to get rid of because it has an extensive root system.  Roots can extend more then 15' wide and deep.  Therefore, digging them is not effective.  They will grow back from the roots left underground.  To add to the problem, they also grow from seed.  These traits explain why they popped up again this year.  Repeated applications of Roundup sprayed or dabbed on should help.  The best time to treat them with an herbicide is when they are actively growing in spring (now) and in August/September.
Q:    I have a silver maple in my front yard that profusely yields helicopter seeds onto my lawn.  They soon sprout and cause a dwarf forest. What can I do other than manually picking the seeds off the lawn?  Will weed killers solve the problem? Will simply mowing them eventually kill them?  Thanks!  R. S., Highlands Ranch, 4/29/03
A:    In addition to manually picking the seeds off the lawn there are other steps you can take to manage them.  Regular mowing will eventually kill many of the ones that sprout.  If you want to use a chemical, you can treat the lawn with a pre-emergent herbicide for broadleaf weeds.  This needs to be done before the seeds begin to germinate.  Post-emergent herbicides for broadleaf weeds in lawns would be an option after they have germinated.

Q:    How can I get rid of the campanula (I call it common harebell) that grows throughout my beds.  It has been near impossible to dig it out without destroying everything else.  Is there anything that is effective as a chemical?  Other suggestions?  Thank you.  D. S., Denver, 5/23/03
A:   Unfortunately, there is no easy way to get rid of unwanted plants (weeds) growing in flower beds.  Chemical sprays and granules that kill the weeds will also kill the desired plants.  The only thing that will help is tedious.  You can use a small paint brush to dab a bit of Roundup on the leaves of the campanula plants.  You don't need to put the Roundup on all of the leaves, just a few from each plant.  Do not get any of the Roundup on desired plants, as it will kill them.

Q:   I am having an awful time with puncture vines. I have a fairly new home, and for 3 years I've been fighting these things.  The more I dig and spray, they multiply.  Thanks, hope you can help.  T. P., Greeley, 7/26/02
A:   Puncture vine is an annual weed that reproduces by seed.  It is essential to get rid of these plants in early spring before they have time to mature and produce seed.  You can hoe or dig up the plants, cutting the plant off below the crown so it can't re-grow.  A layer of mulch can help prevent seeds that are already in the ground from germinating.  Chemical control varies depending on where the weeds are growing.  If puncture vine is growing in the lawn, use a product containing dicamba or methanearsonic acid.  If growing around trees and shrubs, you can use a pre-emergent herbicide that contains trifluralin or pendimethalin.  Round-up or other products containing glyphosate can be used so long as you don't get it on desired plants, as it kills everything.

Q:   Can you suggest any illustrated references for weed identification for Front Range gardens?  Especially something online or that can be obtained from a library?  Thanks.  A. K., Boulder, 7/24/02
A:   There are two books that you might find helpful.  Both deal with weeds found in the western part of the United States.
       "Sunset Western Garden Problem Solver" -- It has a chapter on weeds with photos that might be useful.
       "Weeds of the West" by Tom Whitson -- This is a very extensive reference with photos.

Q:   My yard has become overrun with bindweed.  Is there anything I can do?  It seems to get worse everyday.  I also have 2 dogs and 1 cat. P. C., Arvada, 6/23/02
A:   If the bindweed is growing in your lawn you can control it with herbicides made to kill broadleaf weeds in turf.  It's harder to control it in borders because herbicides that kill bindweed will also kill shrubs and flowers.   Some people resort to dabbing Round-up directly on some of the leaves with a brush to avoid damage to desirable plants.  For more information please see the Planttalk website at  Click on "Weeds & Cultural Problems."  Then click on #2104 "Controlling Bindweed."  When using an herbicide please be sure to read the label carefully and follow directions.  Most products will suggest what safeguards to take to protect children and pets.

Q:   I have mushrooms coming up in my flower bed  and I'd like to know what to use to get rid of them. There is an old tree stump in the bed.  I've tried soap and water and coffee grounds. C. N., Arvada, 6/1/02
A:   Mushrooms tend to appear in soil containing decaying organic matter.  The old tree stump is probably a major factor.  There are fungicides that you might try using, but they often have limited success.  Spading up the spaces between plants to aerate the soil may help.

Q:   How can I kill unwanted grass that grows in my borders which are filled with many perennials & has a covering of wood chips for mulch?  I used to dig most of it out, but find I cannot physically do this anymore.  Thanks.  J. C., Littleton, 5/21/02
A:   To kill the grass that is already present in your beds you can use an herbicide made specifically for killing grass but not broadleaf plants.  One product that does this is Ortho's Grass-B-Gon.  To prevent weed seeds from sprouting I recommend using Preen.

Q:   What is the best way to get rid of Russian Knapweed ?  C. P., Montrose, 5/11/02
A:   I would like to suggest that you contact your county CSU Cooperative Extension office and request  fact sheet # 3.111 on Russian Knapweed.  I believe the information in this publication may help you with control of this weed.

Q:   I have a problem with Sandburs (Cenchrus longispinas). What should I use to get rid of them?  Would Amine 400 2,4.D Weed Killer work?
I live in Gonzales County, Texas. All sand soil.  W. M., Nixon, TX; 5/10/02
A:   Amine 400 2, 4 D Weed Killer is designed for use on broadleaf plants.  Sandburs belong to the grass family, and there are products intended specifically for use on grasses that might be a better choice.  According to Sunset Western Garden Problem Solver, this plant is an annual grass that reproduces by seed.  The goals, therefore, are to get rid of young plants before they produce seeds and to prevent the seeds already in the soil from sprouting.  A pre-emergence herbicide containing pendimethalin, trifluralin or oryzalin will prevent seeds from germinating in turf grasses and ornamentals listed on the product's label.  Products containing fluazifop-butyl or sethoxydim are designed to kill grass and can be used when sandburs are growing around ornamentals.  Don't use these products in or near grass that you want because they will kill it too.  Glyphosate ("Roundup") or glufosinate-ammonium will kill sandburs -- and also any other plants they touch.  Hopefully there is someplace near you that carries products with these chemicals.  Unfortunately, I don't have the common brand names for any of them.

Q: Hello,
   I hope that someone there can answer this question for me.  I have these 'prickles' that are extremely sharp and stick in your feet, in my back yard.  They seem to be here more in the winter, and my father called them ' sheep heads ' or something similar to that.  How do I get rid of them and where do they come from?  They hurt!

Thanks for your time.  J., Parker, 11/15/01
A:    Burs are the fruit or seedpods of various weeds such as Common Cocklebur (Xanthium strumarium), Burclover (Medicago polymorpha), Sandbur (Cenchrus longispinus), Goathead or Puncturevine (Tribulus terrestris), etc.  The key to getting rid of them is killing the weeds before they produce the burs.  You should hoe, cut, pull up or spray the weeds with a weed killer in spring and summer.

Q:    I saw you on a Regis Philbin show and you were discussing how to keep weeds from growing around tree beds.  You mentioned something like putting newspaper and plastic down.  Am I confused or did I hear you right?  I would like to know the proper way to do this.  By the way, I thought you were great.  C. M., Cedar Park, TX, 3/1/01
A:    I'm not sure who you saw on the Regis Philbin show, but unfortunately it wasn't me!  I suspect that the guest suggested using weed barrier fabric or a layer of newspaper several sheets thick to keep weeds from growing in tree beds.  You can spread a layer of decorative rock, pole peelings, decorative bark or mulch over the weed barrier fabric or newspaper.  Plastic is not a good choice in a tree bed.  It would prevent water and air from getting to the roots of the tree.

Q:   I have a question about crabgrass.  I've heard people say that the best way to get rid of it is to just pull it up.  I have so much ( that has crept over from a negligent neighbor's yard) that I don't have the time or inclination to do that.  Is there a spray or something I can use?  N. B., Denver, 7/13/01  
A:   There are several ways to deal with crabgrass.  Crabgrass grows from seeds that were deposited the previous fall.  In springtime you can use a "pre-emergent" herbicide to prevent seeds from germinating -- something to consider for next year.  At this time of year you will need to spray a "post-emergent" herbicide that is labeled as a crabgrass killer.  Any place that carries garden products will probably have some in stock as this is a common lawn problem.  Some products may temporarily discolor the lawn.  Depending on the outcome, you may need to repeat the treatment.  Be sure to water the lawn thoroughly the day before treatment.  Cloudy, cool weather may decrease the effectiveness of sprays so check the weather forecast before spraying.  Be sure to read and follow all label directions.

Q:   After heavy rains, I see a lot of toadstools and/or mushrooms growing in my lawn.  How do I get rid of them without hurting my lawn or pets?  K.C., Aurora, 6/4/01
A:   Two safe remedies for mushrooms in the lawn are core aeration of the lawn and mowing or removing them with a rake.