Higgins is the author of two books, "The Secret Gardens of Georgetown: Behind the Walls of Washington's Most Historic Neighborhood" and "The Washington Post Garden Book: The Ultimate Guide to Gardening in Greater Washington and the Mid-Atlantic Region."
Editor's Note: Washingtonpost.com moderators retain editorial control over Live Online discussions and choose the most relevant questions for guests and hosts; guests and hosts can decline to answer questions.
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Potomac, Md.:
Adrian, I recently purchased a seed packet of "Grandpa Ott" morning glories, but I hesitate to sow them in my yard after someone in last week's chat complained about the reoccurrence of pesky morning glory seedlings. Can this be prevented (i.e., how does one avoid having to be vigilant about weeding out the seedlings)? Will they become a problem if I leave them be? Also, is it too late to direct-seed sugar snap peas? Thanks so much!
Adrian Higgins: This is a brilliant vivid blue and purple variety, well worth growing. Because this is an open pollinated, heirloom variety, not an F1 hybrid, it will come true to seed. In other words, you want it to seed, and I don't think it will prove invasive. I would soak the seeds overnight before sowing to soften the hard outer shell. Peas are a bit late, but I think if you had sown them a month ago, they would only now be germiating because of the cooler spring. Give them a go, but save some for sowing in early August for a fall crop.
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Baltimore, Md.:
Three years ago, I planted a lot of foam flower (tiarella quercifolia) with good results. However, it appears that none of the tiarella survived this winter. Is this plant not reliably perennial in our area? I am also having trouble getting native pinxter azaleas to survive. The area in question is well composted, has the right pH, and drains freely. Any help is appreciated.
Adrian Higgins: The only thing I can think is that it may not be as well drained as you think. Both plants like woodsy, moist soil but the tiarella in particular will resent a wet crown in winter, and will rot. We have had a pretty wet winter this year. I would poke around and see if the soil is well drained or not.
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Washington, D.C.:
Hi Adrian, Thanks for taking my question. Last year I wrote to ask about what you identified as possibly mealy bugs -- tiny white bugs in the soil of houseplants that were producing brown shingles on the leaves and sticky sap all over. As suggested, I soaked the roots overnight in soapy water, doused them with plant oil, and repotted. But the bugs are back in one plant! Could I have a bad batch of potting soil? If not, what else can I do? Would it work just to move the plants outside for the spring and let natural enemies eat the nasty little bugs? Many thanks.
Adrian Higgins: They spend part of their life cycle in the soil. One option is to fill a bathtub and let the pot sit in the water for a few hours. Don't forget about it, or it will drown. I would also at the same time repot and put fresh soil with it.
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Washington, D.C.:
Hi Adrian,
Welcome back! A question for you: Last year at the end of the summer I covered my (tiny, organic, community) garden plot with a layer of leaves and wood chips. Now I'm ready to begin planting again. Someone suggested turning in sand (very clay-y soil) and humus. Does this sound right, and is there anything else you would do? Thanks!
Adrian Higgins: I think I would gather some sand and some peat moss and a bit of lime and work it all in with the mulch you laid, which should have decayed a fair bit by now.
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Arlington, Va.:
What locally available holly trees would you recommend for screening? I am interested in height, but have limitations on width (about 12 ft spread is all that I can handle), and would like to avoid an overabundance of leaf droppings. Drainage in the area could be better, with some sogginess at times. I plan on having a row of about 6-8 trees. Thank you.
Adrian Higgins: The Yaupon holly is native to southeastern swamps and should be hardy enough in Arlington. The Latin name, gird your loins, is Ilex vomitoria.
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Mt. Rainier, Md.:
We have a few raised beds for our veggie garden - is it too early to start sowing seeds for peppers? tomatoes? beans? cukes?
Thanks!
Adrian Higgins: Beans are all right, the rest hold off a couple of weeks until frost danger is past.
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Alexandria, Va.:
Welcome back Mr. Higgins! You've been missed. I want to grow cherry tomatoes this year in pots. When should I put seedlings outside, and what type of potting mixture should I use? Thank you.
Adrian Higgins: You can either sow them directly in the pots, but you run the risk of the seedlings being eaten by slugs or cutworms. If you take this appproach, allow a handful of seedlings to grow to pencil thickness before thinning them to just one per pot. Or, you can start them indoors, it is not too late. In a month or five weeks, set them out into the pots. Or you can wait a couple of weeks and buy seedlings already started in two or four inch pots. Your choices of variety will be limited but you will have seedlings that have passed the danger period. Make sure you have some support in place before the seedlings go in, cherry tomato varieties are notorious for producing monster vines.
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Falls Church, Va.:
Hi Adrian,
I'm a novice herb gardner with a basic question - I planted some basil seedlings in a spot that gets shady around 4:30. Is that enough sun? Will the spot get more sun as we get into summer? Thanks!
Adrian Higgins: Basil will take some partial shade. The bigger problem is that it is not frost hardy. Watch the weather forecast and if nighttime temperatures are predicted to drop anywhere close to freezing, cover the seedlings with a pot.
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La Grange, Ill.:
Help! The wild chives are taking over our grass. For years, we have attempted to pull them out. My husband's solution is simply to mow them. However, they have taken over and grow much more rapidly than the grass, creating an eyesore. Is there a way to be rid of them without killing the grass?
Adrian Higgins: They can be either pulled, making sure you get the bulb. This is an art and a tedious one and best done when the ground is moist. You can use Roundup on the leaves, but I would advise painting it on with a brush, to avoid getting it on the grass, which will then die. The herbicide dicamba is also used on wild garlic. If you apply herbicide, make sure you bruise the leaves first to break down the waxy barrier in the vegetation.
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Baltimore, Md.:
Our Neighborhood House and Garden tour is June 12. My house and garden will be on the tour this year. I want to show off the garden in its finest. I have a nice perimeter garden -- part herbs, part flowers, part vegetables. I would like to know what perennial flowers will be in bloom around that time that I could plant now, or should I just rely on annuals to give color. I have some roses, rudebekia, digitalis, iris, azaelas and daylilies in the garden already.
Adrian Higgins: It takes two to three years for perennials to reach mature, full blooming size, maybe longer. Lavender and early season daylilies should be in bloom then.
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Confessions of a Plant Killer:
Hi. Be forewarned: I have NO green thumb! Here's the problem. Every summer, my boyfriend puts me in charge of watering his outdoor plants (hanging ivy and ferns) when he goes on trips. Unfortunately, when he comes home, his poor babies are wilted and brown, and he looks at me like a criminal. I swear I water every evening (so the sun won't evaporate the water -- is that right?) and assume I'm giving them enough. Is there a rule of thumb as to exactly how much is sufficient? (I'm sure factors such as rainfall, sunlight, etc play into it, so I guess it's not an exact science.) I'd be happy to use a measuring cup if I need to! Also, when we're both away for a few days, what's the best way to water them? Drench them on our way out the door, or just let them be thirsty for a few days? Thanks for your help! (My boyfriend thanks you, too!)
Adrian Higgins: Rainwater will never be enough to sustain a hanging basket, which is one of the most demanding forms of gardening. I take my hanging baskets (all right, two of them) and dunk them in the fish pond. I wait for all the bubbles to come out. That way, I know the root zone is fully soaked. That will keep it going for a few days or more. If you don't have a pond, fill a five gallon bucket with water and do the same. Plants in shade will need far less watering than those in full sun.
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Washington, D.C.:
I recently joined a community garden in Washington DC. Because this is an urban site, we are using raised plant beds and creating a barrier against the existing soil and bringing in new soil. I will likely be filling my truck with top soil from a supplier in the suburbs. What suggestions can you give for creating a healthy soil composition to grown a variety of vegetables? Should we include sand and/or leaf mulch in the mix? Also, what general guidelines can you give for enhancing the soil over the growing season and from year to year? Thanks for the help!
Adrian Higgins: I think I would organize a compost committee and buy a chipper shredder and a good screen. Let everyone drag their plant debris to the compost site, where it is shredded, and allowed to decompose. After a few months, it is then screened and ready to add to your gardens, either as an amendment or a mulch. In the meantime, you can add peat moss and bags of compost and a little firewood ash, and get the garden going for this year. Don't use fresh manure, it can carry pathogens that don't mix with food plants. It would be a good additive, though, for a compost area.
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Front Royal, Va.:
Adrian,
This is about grass seed. I have a rather large area that I need to seed and I don't know what to do to keep the birds away from it all until it takes root. Any suggestions besides putting down straw? Thanks
Adrian Higgins: I have known a light layer of sand to be a very effective mulch. It keeps the seed moist and confuses the birds.
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Vole City, Va.:
Regarding the tiarella plantings--I have had rather poor luck with mine too, but it was because of voles tunneling underneath them not so much the soil conditions. I am still trying to find ways to fight these little critters humanely, but I think it's a losing battle. Any suggestions? Thanks much.
Adrian Higgins: That might be the problem. I have not had a problem with voles, thankfully, but even if I did I wouldn't want to use the poison baits that are available. My colleague Barbara Damrosch is planning to help us rid the world of voles in a forthcoming column. Stay tuned.
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Clarksburg, Md.:
Adrian, is it too late to cut off tree branches? I have a number of relatively young trees whose branches try to scrape me off of the riding mower when I'm cutting nearby. Each year it's getting more and more difficult to maneuver under or around said offending limbs.
Adrian Higgins: The optimum time is in winter dormancy, but anytime is ok for some trimming or remedial pruning. Less is more, though.
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Silver Spring, Md.:
Last year I planted six nandinas (firepower I think - leaves turn red in fall/winter). All six were beautiful and full of leaves. I planted four of the six nandinas in a mainly shaded area along the side of the house and now all four are barren of leaves (occurred during the winter months). The two nandinas placed along the fence(a sunnier area) still have leaves on them. Will the leaves grow back on the four barren nandinas? I don't want to relocate them if unnecessary, so what advice do you have for me? Thanks, Adrian, and glad to see you return to help us gardeners!
Adrian Higgins: Nandinas will lose leaves in harsh winters. The last rating as harsh in my book. It will refoliate in the coming weeks.
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Arlington, Va.:
We have a very large oak tree in our backyard that was not well managed as it grew. The consequence is that it has a large long limb that extends well over the fence to our neighbor's yard. Our neighbor has asked us to remove the limb, and for the sake of good relations, we have agreed to look into the matter. What time of year is best for this kind of tree surgery? We don't want to stress the tree and make matters worse. Thank you for your help.
Adrian Higgins: Again, winter dormancy is the least stressful, though oaks can be pruned at any time. If a windstorm broke the bough in half in August, obviously you would want to amputate it then. There are some instances where removing a large bough may imbalance the tree and make it more prone to fall. If it is a sizeable specimen, I would get a certified arborist to give an opinion.
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Kensington, Md.:
Greetings, Adrian,
We have a child, a new puppy and a lawn that we didn't treat in time with Scott's Weed and Feed. What child-and-pet-friendly weed treatment do you recommend for our lawn? Thanks!
Adrian Higgins: I would rent an aerator or get someone else to give it a good soil aeration and then seed it, and then repeat in the fall. There are a growing number of organic feeds that you can apply. While you are doing this, get a soil test, this will give you a better sense of nutrient deficiencies.
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Olney, Md.:
I have a woodsy hilltop that I'd like to put a bench on, and grow some shade-tolerant ornamentals around. After pulling up the brambles, I fear. Suggestions?
Adrian Higgins: I had exactly the same situation in my garden. The first thing I did was create a pad of flagstone that was five feet by six feet. A bench is of no use unless it is flat and out of the mud. There are lots of shade perennials to pick, including the aforementioned tiarella or foam flower. I have sweetbox, lamiastrum, Euphorbia amygdaloides and Senecio aureus.
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Brooklyn, N.Y.:
Glad I found you today, for I have a city gardening question. I need a quick, tall screening from the neighbors' property, and all I can think of is bamboo. Our back yards are tiny, and I need something compact but tall. If bamboo is ok, could you suggest a variety? If bamboo is a mistake, as many friends tell me, can you suggest an alternative? Thanks for your help--I just can't look at that cinderblock garage any longer! Gotta do something!
Thanks, Kas Schwan
Adrian Higgins: Can you get a carpenter to build a trellis agains the wall, and then grow vines on it. Moonvine flowers and morning glories would provide instant screening while you raise something slower like climbing hydrangea. Wisteria would grow quickly, but needs a lot of pruning maintenance. Another option would be hardy kiwi.
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Alexandria, Va.:
If I take a photo of a plant and email it to you, will you identify it? I don't know what it is.
It has light green longish leaves, a little fuzzy. The plant grows about waist/chest high with purple flowers. I heard it might be used for tea (?) Thanks!
Adrian Higgins: yes, email it to higginsa@washpost.com
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Arlington, Va.:
I have a small townhouse backyard in Arlington with hard-pack, poorly draining clay soil with only a few months of direct sunlight. I aerated, fertilized, and seeded last year, which helped, but I still have a very mossy covered, poor-draining mud pit. I like to entertain quite a lot (i.e. high traffic) and would very much like a better solution. I am thinking about laying sod this year, but am looking for ideas on which sod to use and on how to better prepare the soil to accept it. Any suggestions? Thanks for taking my question.
Adrian Higgins: Feet and gardens don't mix, especially in wet clay soil. It would be a waste of money, I think, to lay sod if you have standing water, the turf will recede. You first must build up the area to avoid waterlogging. There are standards for turf, ask your nursery if they can tell you what percentages of different grass varieties are in the turf.
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Dividing plants:
Is it too late to divide my hostas that have poked through the ground, as well as my too-big mums?
Adrian Higgins: No, but be very careful with the hostas not to damage the burgeoning growth.
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Burke, Va.:
I was very inspired by the blooming cherry trees and my first spring in our new house. I would like to plant a small cherry tree in from of the house. How far away from the foundation would be safe for such planting?
Adrian Higgins: Depends on the variety, but I would allow at least 10 feet.
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Alexandria, Va.:
I'm trying to grow grass in a shady backyard. I've put down seed, and fertilizer (though not starter fertilizer) and have been watering most every night. Are there any other suggestions to get this grass coming up?
Adrian Higgins: Fine fescues are preferred over tall fescues for shady areas. Seeds will take as long as three weeks to germinate, but they need a light misting, not a soaking. I would advise repeating the process in September, which is the optimum time for grass seeding.
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Arlington, Va.:
We've got a birch tree in our front yard (it's quite tall 15-20 feet), but last year it didn't get many leaves. I afraid that the same thing is going to happen again this year. Any advice to help this sad-looking tree?
Adrian Higgins: This is a sign of stress, perhaps. Birches don't like drought. And if it is a paper birch it may well be succumbing to bronze birch borer. Watch too for aphids this spring. It might be time to put in another tree better suited to our hot climate.
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Charlotte, N.C.:
I hope you take VERY basic questions, too! I want to put flowers at the front of my house. There is the usual red clay North Carolina soil, which I assume I need to dig up. What I don't know is what I then put over the clay -- potting soil, regular 'ol dirt, mulch ... How do I best assure that my flowers (low-maintenance annuals, probably) will thrive?
Adrian Higgins: You can just improve the planting holes with bags of compost from the garden center, but soil building is a longterm endeavor that involves adding compost or shredded leaves once or twice a year and letting the worms work it into the soil. Alas, we must leave it here for another week. Thanks for all your questions, and enjoy the spring.
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