Adrian Higgins on gardening

Tracy A. Woodward/The Washington Post
Sep 22, 2016

Washington Post gardening columnist Adrian Higgins took questions on gardening.

In your article on the mall you mentioned they use a low impact herbicide. Would you be able to name the product as that has been a long standing question for us. Pulling weeds by hand is a lot of work in a large lawn but we are concerned about the effect on the lawn and runoff of strong herbicides. Joe Bell

Greetings all. Let's hope the new season brings cool weather, low humidity and some RAIN! I think I the herbicide is called Tenacity, and it's available to consumers. It's expensive but used at very low rates. 

Be sure to check out Adrian's most recent column, on the project to renovate the lawn on the National Mall.

How can a homeowner in the Washington, D.C. area have a nice lawn without using multiple sprays and other potions to kill weeds? My established lawn behind the house looks like a weed farm. Desirable grass varieties are rare. The one-year old lawn in the front looks fine now but hardier weeds are moving in and staying. I like some diversity but not a weed eco-system.

A lawn is not a stable landscape feature. It requires continual maintenance to look good. My lawn at home is pretty bad, but I invest my time and work in the ornamental beds, the vegetable garden and the pond garden. Now is the time to fix patches. What most people don't think about is that the variety of fescue that you pick is very important, you should seek out cultivars bred for this region and climate. The ones used on the Mall, interestingly, are Falcon V, Turbo and 3rd Millennium. 

I have six justin brouwers boxwoods planted, but one of them gets a lot more sun than the others. Twice it has turned brown at the end of the summer and died. (I replaced it last year, same thing happened.) The grower tells me it shouldn't be the sun and thinks it may have a drainage problem. (it doesn't). But I have another theory. Both this summer and last, my daughter was dog sitting at our house and the mutt was regularly using that particular boxwood as a hydrant. Do you think that could be the cause?

Yes, I do. Apart from anything else the urine is acidic and boxwood need a more base soil pH. I would put up some sort of barrier that would keep the dog off it. 

I was the person who has been growing tomatoes grown from seeds from FSU's Klee research lab, Garden Treasure and Garden Gem. I must say these are the best performing tomatoes I've ever grown. I've had a great harvest of the beefsteak style Garden Treasure tomatoes and a good (didn't plant as many) of the Garden Gem tomatoes. No sign of blight anywhere and only a few stolen tomatoes due to the fencing I put up. I'm totally buying more seeds next year.

They have done a lot of research on breeding superior hybrids, so that's good to know. They may be geared toward the professional grower, but the home gardener can certainly benefit from the work. Heirlooms can be difficult to raise successfully, even if the foodies don't like to hear that. 

Hello Adrian, glad to see you on the chat line again. What are thoughts on dealing with this drought? Forget trying to save the lawn and just water the shrubs and perennials? Should we consider reseeding the lawn in the fall, or will it bounce back if we get some more rain?

Good question. I think at this point it's quite important to start soaking ornamental and shade trees, because those are the plants you can least afford to lose. Give each a good drench, but then move on -- don't drown them with love. One long soaking is much better than daily spraying.  

Crape myrtle and rose of sharon: when and how to properly prune???

Both benefit greatly from formative pruning, i.e. shaping when they are young, in their first two or three years in the garden. I would prune both in winter, when you can see the outline. This requires an eye, and restraint. Do not, please, top your crape myrtles, this is a widespread but erroneous practice.  

Two weeks ago I planted grass seed bought from a local home improvement store. I faithfully followed the directions on the bag about dethatching and adding a bit of topsoil, and have watered twice a day for 10-15 minutes to keep the soil and seed moist. However, little to none of the seed has germinated. Did the unseasonably hot weather this month create a problem? Should I give up until spring?

Tall fescues are slow to germinate, as long as three or four weeks. Just keep it moist and be patient. You could also scatter a bit more seed, still plenty of time. 

I was looking to put some sugared rose petals on a cake but read that we should only use organic roses and that they're nearly impossible to find, do you know anyplace that would sell them in our area? Are those flowers I've seen on wedding cakes online organic? I ended up using some dianthus from my flower pots as a decoration and didn't actually serve the flowers to any guests. Thanks for your help!

Does Whole Foods, I don't know? The best way to grow organic anything is to do it yourself, because then you can be certain. 

I had a large maple tree that shaded the front of my house. It was slowly dying and started dropping large dead branches, so I had it removed back in February, and the stump was ground out. Now I want to plant another tree, but when I started to dig a hole, I found massive tree roots in the lawn. If I call a landscaper, will their auger go through roots, or do I call the stump grinding guy back?

I'm not sure if the roots are from the removed tree or a living one nearby. If the former, you can make short work of it with a sharp axe and mattock to create the new planting hole you need. If the latter, you can still use the mattock and a shovel to excavate around the root and plant the new tree around it. 

When is the best time to use milky spore?

I'm not sure, maybe one application in a month and another in early spring. You want to do it as the beetle larvae hatch from eggs. Anyone out there who can advise?  

Hi Adrian, I feel like I should hardly dare to approach the great Adrian Higgins with my lowly question. I am not being facetious! You know so much and I know nothing. Well, my question is that I have a small Norfolk pine in a pot that I used for a Christmas tree last year and it is suffering. I want to move it to a bigger pot and keep it alive. Is this something an awkward, ignorant person can do? Do I just go to the local hardware/lawn store and buy a big pot and some dirt? And move it over? I have a south-facing bedroom window it sits next to. I don't know if this is even where I should ask a question about an indoor plant. Thanks for your time.

My servants are just bringing me your question on a velvet cushion. Let me just adjust my tiara, here. Repotting is a fairly easy task, and generally you want to upsize the pot by about two inches but not much more than that or the plant will suffer root rot. Repotting is generally done in the spring in advance of growing season, but I think if you're in the mood to do it now, that's ok. Just make sure that the roots are not potbound and tease them out a bit. Use fresh potting mix to replace soil that is lost in the process. In the wild, this tree gets to 100 feet, so at some point it will outgrow your abode. Just so you know. 

Good afternoon, Adrian, and thanks for taking our questions. The south facing side of my yard receives little sun because years ago the owner planted pine trees as a border. Poison Ivy has pretty much repurposed itself as groundcover (the area is approximately 40’ x 10’), which I need to address. Would 18 – 24 inches of hardwood mulch do the trick? I live on a well and have outdoor cats, so I’d like to avoid using Roundup or the like, but will do so if I must. Thanks Adrian. I miss your weekly chats….

I suppose you could lay black plastic as a way of killing the poison ivy, but that will take months, and better done earlier in the year. You can't just lay a thick blanket of organic mulch and expect the vines not to grow through it, they will.This will also play havoc with the soil conditions for other plants. This sounds like an instance where Roundup or some other herbicide is necessary, but even after you have killed the vines you will have to take care in pulling it and throwing it out. Long sleeves, gloves, long pants and boots all apply. It's a nasty plant. And don't burn it! It gives off toxins. 

my front yard has large patches about a foot in diameter where the grass has died. the grass around it is thick and green. could this be caused by a fungus? many of my neighbors have the same problem. any suggestions?

This is probably a disease called dollar spot, caused by the extreme heat and humidity of the past few weeks. It can be controlled with a preventative fungicide application, but at this point, I would simply scratch it out, top dress the patch, and re-seed. 

I'm new to the concept of gardening in the mid-atlantic - and want to create hanging baskets for my english basement "porch." What will work in the fall weather? And are there any herbs that will work this time of year?

My standard pitch on hanging baskets: They look easy but are actually the toughest form of gardening -- the stresses on the plants in our climate are many. If you plant a hanging basket, be prepared to water at least once a day. Now you could grow herbs in pots -- easy peasey. I would sow some cilantro seeds, and plant some parsley. It's getting late for basil -- it will only last about another month, but might be worth it. 

Any advantages or disadvantages to planting a rhododendron this weekend vs. waiting for April? Thanks.

It is better to plant most woody plants now, so that they can get over the transplant shock before the heat of next summer. (Magnolias have fleshy roots and are better planted in the spring). The biggest mistakes with planting (in my view) are one) the shrub or tree is set too low (the root flare should be an inch or two above grade); two)  the plant is not set vertically (this seems like a no-brainer but you'd be surprised); and three) folks think a new plant should be watered constantly. It should get a deep soaking and then left alone with perhaps another deep watering in a month or two. 

Adrian, thank you for bringing attention to the efforts to refurbish the lawn on the mall. It's been pretty terrible for years--just basically a field of dirt in many places and hardly a showcase for the nation's capital. Will the Park Service actually erect some kind of low barriers to discourage people from walking on the lawn after it's restored? Could all of this be in vain in a few years?

I think with the hiring of a groundskeeper there will be a concerted effort to close areas as needed for regeneration, but it will be a huge challenge. There is a large contingency that believes the underlying democratic symbolism of the Mall means that it should be viewed as a space open to everyone at all times. I do believe that many people don't understand the damage that merely walking on grass can do. I remember writing about a public square in New York whose lawns and plantings had been compromised by pigeons landing and walking on them over the years. 

I'd like to lower the height of my boxwoods which are growing too tall and starting to block my windows. My limited understanding it that I need to remove branches to create "holes" in the canopy to allow light to penetrate to the inside of the bush. Is that correct? Am I removing entire branches, or cutting back a four-foot long branch down to a two-foot long branch? How big should the "hole" in the canopy be? How many should there be? What is the best time of year to do this? Thanks!

You're sort of conflating two pruning principles. Boxwood need that thinning to encourage light and air to reach the interior of the shrub. But it sounds as if you need to simply reduce the height of the shrub, which is possible but you will leave a stub that may take two years to fill in. (which is ok). I would wait until winter dormancy to do this. If you prune boxwood now, you may encourage fresh growth that will be frost damaged this winter. 

With the weather still pretty hot & humid, is there any point in sowing anything for the fall? Any recommendations? Is it still too hot for artisanal lettuces?

I have just sown lettuce seedlings and they are germinating at a decent rate. I hope to sow some spinach this weekend.  

I have a treasured gardenia that was my grandmother's before she passed. It loves the summer months outside on my deck, and lives less happily (slow growth, some browning leaves) in winter months. Should I consider leaving it outside this winter? I'm scared of killing such a lovely plant, but it really doesn't seem to thrive indoors.

I think it would be too risky to leave outdoors, even with protection and mulching. The last two winters were pretty rough. But you're right, it doesn't like overheated rooms in the winter. Ideally, you should find a bright room and shut off or reduce the heat to it so it can stay in the 60s. Any chance of that? I like cool rooms and thick sweaters in the winter. 

The green shrub (maybe a boxwood) between my neighbors and my yard has an infestation that appears to be scale (white bugs that are covering the shrub like snow). Does it have to be cut down and insecticides added? Can I use this to convince my neighbors that we should remove it completely? It has a lot of bird life, which I hate to remove, but boy does it get big (at least 12 ft tall right now) and prevent my yard from getting sun. Suggestions?

Scale infestations are a direct result of stress on shrubs, probably from the drought. Insecticides are only effective when the crawlers emerge, so timing is key. Sounds like this shrub should be cut down and placed in a bag, along with the pests. Alas, we have run out of time. Hope to see you in this space again in a month or so. Thanks for joining us. 

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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.
Kendra Nichols
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