Adrian Higgins on weeds, herbicides and all things gardening

By Jennifer Heffner For The Washington Post
Sep 19, 2019

Washington Post gardening columnist Adrian Higgins took questions on gardening.

We renovated our lawn last year but, in certain areas, still ended up with a substantial amount of crabgrass by mid summer. Is it a fruitless exercise to overseed this fall without pulling out all the crabgrass? We don't want to use herbicides but are not sure we have the energy to tackle all the crabgrass.

Greetings all. My story this week is on alternatives to herbicides. My basic point is that you need to first get rid of established weeds, and then be present in the garden to stay on top of new weeds. 

Crabgrass is an annual weed, so the conventional approach is to use a pre-emergent herbicide in early spring to prevent germination. If you have crabgrass now,  don't let it go to seed. The bigger issue is to build your turf so that the crabgrass and other weeds that are eager to grow there will not get a toehold. 

Ground ivy has infiltrated my yard and has taken over a substantial area, crowding out our fescue in the process. I’ve tried to manually pick them out but feel like it’s a losing battle. Their roots are everywhere. Any suggestions?

Ground ivy is another symptom of receding lawn. It is  also an indication that you have areas that are poorly draining and probably compacted and until you address that underlying condition, your grass won't become vigorous enough. 

Greetings, fans of Professor Higgins. Producer here with a link to Adrian's most recent column, on why herbicide sprays aren't the best way to deal with unwanted plants, and what to use instead. And in case you missed it, here is his recent story on Tony Avent, one of the most enduring figures from the arcane world of elite horticulture, which appears in The Washington Post Magazine this Sunday.

Adrian, I bought a hoe at Home Depot. The blade is covered in plastic like it was dipped in a plastic coating. I've never seen this before. How do I get this off? Where can I get the blade sharpened?

In the old days, especially in Europe, itinerant knife sharpeners would appear and put an edge on all your tools. They seem pretty thin on the ground these days. You will need to buy a file, so that you can put the edge on your hoe yourself. (Wear workgloves). As I mentioned in my story, garden hoes are too blunt to effectively slice through weeds, and you need to seek out hoes with thinner, sharper blades. 

We have a major infestation of stilt grass in our neighborhood outside Charlottesville. After soil testing our moss-covered yard last fall, I limed the yard, raked out the moss, then top dressed the yard with excellent composted soil and planted tall fescue in the spring. The grass looked great until July, but then died. Then the stilt grass took over. I would be happy with stilt grass but it does back to nothing in the winter before roaring back again the next year. Suggestions? I just reseeded a few weeks ago and that grass is coming along.

The optimum time to establish a cool season stand of turf is now, not in the spring. I would try again, but I would set the mower on its lowest setting first to try and remove all the seedheads of the stiltgrass. Again, this is an annual and the key to beating it is to break the cycle of seeding, and then crowd it out.  

What is the best online resource or app to ID weeds?

Virginia Tech has a good website for this: https://weedid.cals.vt.edu/ 

Adrian, I really enjoy your columns, but I have a request. When you are discussing plants, could you include the binomial names as well as the common names, or at least a link in the on-line version so we can find out more information? As an example, today you mention trumpet creeper, but an online search turns up several species, many sold in nurseries. I don't know which of these, if any, you are referring to. Thanks.

That would be Campsis radicans. I try to avoid using the botanic names unless I have to, for fear of readers thinking this an exclusive club. 

I'm sick of the bare patch of ground in front of my apartment that always gets overgrown with various opportunistic invasive plants and has to be cut back to the ground. I'd like to plant similarly aggressive native plants (New England, Boston area). Thoughts? Or should I just go nuclear and plant mint in them?

My lawn really suffered in this drought. I lost most, if not all, of the grass I planted in the spring. Quite frankly I did not water the lawn until it was too late. Right now my lawn is half dead grass and half weedy grasses. Should I dig up all the turf and reseed the whole lawn? The soil is so dry I am concerned the new seed will not grow even with appropriate watering. I don't want to end up with a lawn that is patchy or barren because of the dry soil. I have even thought about sod but am concerned about the cost. What do you suggest? Thank you

I'm writing soon about this extreme dry spell and talking about lawn stuff, but I'd say -- try again over the next month. Time to drag out the hoses. 

Why didn't you recommend straight white vinegar as a weed killer for weeds in hardscape? I use it all the time on my patio and driveway and the weeds are dead in a couple of days. I don't remember if they return in that spot. I also use them on the brick sidewalk in Georgetown outside the church where I'm a volunteer.

I sort of made an oblique reference to vinegar, namely that household vinegar is too weak to be highly effective. However, it will knock back top growth if applied several times.  

I have an area about 5' x 10' in front of my kitchen window that has a lot of creeping sedum (I don't know what variety) which I want to keep, but it also has a lot of weeds. When I pull the weeds, the sedum comes up too; it doesn't have much of a root. If I rip out everything, can I then put the sedum back in the dirt? It seems pretty hardy. There's a patch of it growing on my concrete walkway, with no dirt at all.

Watering the area thoroughly the day before will make the weeds easier to pull. You can set the sedum back. 

We have a sloped, shady backyard that was neglected for a couple of years before we bought the house. It's covered with English ivy and pachysandra, along with some shrubs that need to be thinned, but some of which we'd like to keep. I'd hate to lose the pachysandra--I don't mind it, and it holds the soil well on the slope. Is there any hope, though, of getting the ivy out without killing the pachysandra? I spent about 3 hours the other day and only managed to clear about 10 square feet of ivy, and got a bit of poison ivy for my efforts.

The first thing I would do is scrutinize the area for poison ivy. That is one weed I would use Roundup on. English ivy is actually quite easy to rip up, especially if you have a mattock to get to the stubborn strands. Make sure you are wearing longsleeved shirts and long pants, etc, and work gloves, in case you come across poison ivy. Be careful. 

I'm a novice at keeping plants alive. We moved recently and have a tree box in front of our home that is mostly filled with the roots of a large mature tree. While the tree cover is wonderful, the box itself looks rather unkept. Any recommendation on something that doesn't require much soil or light to fill the tree box? Best strategy for getting something to survive?

Tree boxes are not conducive to ambitious gardens. I would try something like mondo grass or, predictably, liriope. Moss is another option, as are little bulbs such as snowdrops and chionodoxa. 

Do you have any favorite YouTube channels for plant info and care?

The short answer is no, but one of the keys to how-tos for hardy plants is to find someone in your region. Perhaps others have some favorites. Johnnys Selected Seeds has some videos pertaining to vegetable gardening. Also the Maryland Home and Garden Information Center has an array of useful videos. (Grow It, Eat It) or at least used to.

Another reader with a ground ivy "lawn". You mention that it is a sign that the soil is poorly drained and probably compacted. How does the novice homeowner best go about addressing this problem?

I'd have to check on that, but you may be right. 

Hi Adrian, After reading your article about weeds this morning, I have a question or two. We have a small yard in Silver Spring, so most of our underlying soil is clay, with a little topsoil. The lawn is a mix of weeds and grass and I am trying to get a better lawn. So I have been digging out the clay and mixing in a mix of topsoil and compost. Fortunately we have a friend near-by who actually wants the clay, so that is easy to get rid of. So my first question, is: Am I nuts? This is a lot of work and it seems that the clay once it mixes with the topsoil and compost for a few weeks basically incorporates all of that and becomes rock hard again. 2nd question, is there a better way? My perception of the problem is that because of all of the underlying clay we don't get a lot of water penetration into our soil, so the lawn dries out fairly quickly, and the grass dies, allowing weeds to come in. The clay also seems to keep the grass roots out. So what can be done? Other people have nice lawns (not in our neighborhood though), so it seems possible. Thanks.

One of the best ways to build up a clayey lawn is to shred the  fallen leaves in the fall with a mulch mower, and let them break down over the winter. This will add organic matter that will improve the structure of the soil. You can also add leafmold and compost on a regular basis, and that will have the same effect. Know though that homemade compost can be loaded with weed seeds. Building up clay soil this way takes several years, but is quite do-able.  

The wild patch of land across the road from our house is a small flat strip that then drops down a steep slope. There are wild-seeded trees, wild grape vines, other competing growth, and generally just brush. Our municipality has never done anything to maintain it. About 25 years ago, I had hundreds of daffodil and narcissus bulbs left over after dividing mine, so decided to beautify the patch across the road by "naturalizing" the bulbs there, just pushing my bulb-hole planting hand tool into the ground, shoving a bulb in each hole, then covering with the soil in the planting tool. After a couple years the patch began looking beautiful and cheerful each spring, and still does to this time. One tip: If you live in a snowy area where your jurisdiction spreads salt, don't both to plant within a few feet of the road, because the salt will kill the bulbs.

I love the idea of taking daffodil increases, and planting them in barren areas. If they have enough sunlight, the bulbs should spread, year to year. And deer won't eat them.  

I store my Roundup in the garage in a container since it does give off noticeable fumes. Roundup is so effective I really don't care about its potential harmfulness. How much at risk am I for using it?

The Roundup controversy gets to issues beyond my ken, namely the tort system in our society. The pesticide regulatory bodies around the world have not linked it to cancer, I don't have a problem using it myself on those grounds, although I would minimize contact with my skin and wash my hands thoroughly afterwards, especially if dealing with the concentrate form. My point today is that relying on herbicides is not the way to garden, the way to garden is to attend to the underlying issues with weeds, which actually comes down to how much time people want to spend in the garden.

Finally my house is looking less like the before on an episode of Flip or Flop. The instructions I was given was to water daily. I have been watering the beds planted with dwarf boxwoods, hydrangeas, pachysandra and echinechia with a sprinkler daily and using a tree gator for the little red maple. I'm guessing the daily water should happen for a month or so? Should I water the beds on milder winter days? Seems to me like we've fallen into a drought patter so I cannot assume mother nature will provide. I'm in Fairfax just outside the beltway.

Plants need watering now, especially young woody plants. HOWEVER, watering means one good soak and then hold off for several days or a week or more before re-watering. If you keep the plant sitting in wet soil, it will probably croak. This is especially true of boxwood, which doesn't do waterlogging. 

For removing small poison ivy plants, I use the Washington Post method. I slip one WaPo home delivery bag over my arm and secure it with a rubber band for protection, then slip another one over that and pull up the vine. I slip the bag over that and discard it and replace with another bag. Works like a charm. On the question of formal names, I understand not wanting to fill your print column with them, but links in the on-line version would sure be helpful.

Thank you for the advice. Get those home deliveries, folks!

Do you have any recommendations of a good month-by-month calendar to plan for a nice flower garden, care of shrubs, and a half-decent lawn? When am I supposed to do what? I realize this is a long question, so I'm wondering where to find a good checklist.

That would be useful, though I've found these calendars can be too rigid, not related to your growing zone, and assembled by people who may not be gardeners. Gardening is a process and a conveyor belt. What I'm doing in the garden now will pay dividends a) this fall b) next year c) forever. 

Hi Adrian, Last year, I asked you about stiltgrass. Your answer was "flamethrower" =:O

Stiltgrass has become a huge problem. It's taking over the world. It's an annual and is now going to seed. I think it will take intensive effort in your own yard to push it back. On public lands with great acreage, I don't know how you would control it short of getting an army of people to work on it. At least it's prettier than kudzu. Anyway, I'm afraid we've run out of time. See you here again soon and thanks for the questions. 

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Adrian Higgins
Adrian Higgins is The Washington Post's gardening columnist. Read his latest columns and stories here and follow him on Twitter.
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