The Garden Plot

Adrian Higgins (The Washington Post)

Got a chronic case of green thumb? Like getting your hands dirty? Adrian Higgins, garden editor for The Post's Home section, is here to help. Higgins is a firm believer in "tough plants for tough times" -- the varieties that combine good looks with stiff resistance to disease and pests. He currently rules over a garden filled with spring bulbs, daffodils, ornamental onions, perennials, asters, yarrows, hostas and day lilies. Higgins, an avid organic gardener who believes chemicals are a last resort, also tends his own herb and vegetable gardens where he grows peas, garlic onions, lettuce, rhubarbs, radishes, carrots and more.

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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Richmond, Va.: Your columns have been extremely helpful to me as a "new" gardener.

I had "soil" which turned out to have a high content of sand put into a large raised perennial bed last fall. Because of settling, I need to build it up and enrich the soil two or three inches. Can I put it over the dormant perennials or should I dig them up and replant?

And... is it too early to put in grass seed in Central Virgina?

Thanks again for your help.

Adrian Higgins: Most perennials are not yet dormant. Those that are spring bloomers such as columbines, perhaps. No, you don't want to pile soil on top of them. You must first dig them up, work the soil into the bed and replant them so that their crowns, the point at which the roots become the top growth, are at or just below the new soil level.
Cool season grasses struggle somewhat in Richmond, because of the heat and humidity. I believe many people in Richmond grow zoysia or ornamental bermudagrass, though much cool season types such as turf type tall fescues are used. Select a variety that has been bred for southern climates. You local extension office or Virginia Tech should have a list of recommended varieties. You can start seeding now, probably until early November in Richmond.

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Washington, D.C.: Bed preparation question: there are tree roots probably from an oak tree about 4 to 20 inches from the surface in the patch where I plan to plant flowers, grass and perhaps a few schrubs. How important is it for me to try to have all the roots completely ground? The stump has been ground out along with a few other surrounding roots but my tree peoople failed to get all the roots. Aren't rotting tree roots feeding ground for termites and other ground creatures? But isn't it true that as long as I do not plan to plant big trees, it is ok to leave a few roots there?

Adrian Higgins: If I find old roots in the way of a bed I am preparing, I take a very sharp axe and sever the roots and then pry them up with a strong fork. Don't do this, or any heavy garden work, in flip flops, sandals, sneakers or other inadequate shodding. If the roots are immovable, I plant around them.

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Washington, D.C.: Adrian,

I've planted some perennial curbside (treebox) beds this year with the idea that in the cold months they'll be cut back to the ground and survive their winter coat of snow, uncollected leaves and road salt.

Can you recommend a groundcover that I can dress these beds up with? Something to give the beds interest before and after their peak. I need something that will survive the rather exposed positions next to the street.

Thank you

Adrian Higgins: I am not sure you can combine ground covers with perennials, it's either one or t'other. A good ground cover for tree boxes is liriope, overused but pretty nevertheless.

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Dupont Circle, Washington, D.C. Novice Gardener: I just moved into a new rowhouse. The front yard gets partial sun and is home to three scraggly, unattractive rhododendrons that I'd like to replace with ferns. Will ferns do well in this area? Is it too late to plant them, or should I wait until spring?

Adrian Higgins: Ferns will only do well if they have deep soil and continual if not continuous (there is a difference) moisture and a modicum of shade. These are difficult conditions to recreate in the city on thin soil and dry sites, though not impossible.

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Bluemont Park, Va.: Good Morning
I live next a beautiful park that unfortunately has the urban plague of rats. I have recently seen them out and about in my garden of both over grown perennials due to our abundance of rain & several shade beds. We have had to resort to some bait stations because of their numbers. I am no fan of poisons and know what they are doing to my chipmunks and other beings. Do you have any suggestions or hints for dealing with them in a gardening situation? I am very apprehensive out about getting out there and mucking about. I just don't know what is going to be waiting for me under the leaves. Many thanks.

Adrian Higgins: The advice from rat catchers is don't have a compost or feed birds, these provide sustenance for rats. I think the whole city is having a big rat problem at the moment. I would call the bureau of vermin apprehension.

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Norfolk, Va.: Howdy Adrian! I've got strawberries growing in a pot on my deck, and for several weeks this summer was able to pick enough every day to flavor my lunchtime shake -- but since the first good round of ripening, I get tons of blossoms, berries start to set and ripen, and then they all get a black spot on one side and nevery fully ripen. When I mussed the plants this morning, bunches of what looked like fruit flies flew out. What can I do to stop this? I still have blossoms forming and would love some more strawberries before it gets too cold (sometimes November here!)

Many thanks!

Adrian Higgins: Strawberry blooms suffer from a disease called gray rot, which is prevalent in wet years like this one. Touching one infected fruit and then others will spread the fungus. Remove all infected fruit and place the pot in a sunny site that gets good air circulation.
I suspect strawberries in pots are a one or two season proposition, since they are heavy feeders and like moisture, and do better in a good garden bed.

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Finksburg, Md.: Hi,
I have mature cherry tree that is invested with bugs. The usual course is a curling of the leaves in late spring/early summer, and infestation with spider webs and loss of all leaves by the end of July. What can be used to control this infestation (besides chemicals) -- I have several bird nests in the tree and would hate to injure the birds with chemical sprays. Do I have to just bite the bullet and spray?

Thanks!

Adrian Higgins: THis is probably the fall webworm, which has been bad this year. I would remove the branches that contain the webs (if you can reach them safely), you can spray the caterpillars when young with a bacterial agent called Bt, or simply let the birds eat the worms. Since the tree's leaves have done most of their work for the year, this pest is not as devastating as the spring arrival of the Eastern tent caterpillar.

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Arlington, Va.: I have a bed of peonies that is slowly getting established. Could you suggest some plants to go between/around the peonies to provide some color and help keep weeds down during the long period when the peonies aren't blooming? Thanks!

Adrian Higgins: I think peonies dislike competition from other perennials. My advice would be to let them grow together. You might plant some bulbs of lycoris, which bloom on slender stalks in August.

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Centreville, Va.: Hi Adrian, I'm not sure if you're the right host for this question, but since it's in the garden, I figure I'd give it a shot.

I've noticed over the past two years a "funky" smell coming from our fireplace that is prevalant in dry weather only. (When it's wet out, the smell is minimal.) We live near a rather extensive stream valley and I've noticed the same smell there as well. (I'm pretty sure it's some kind of mold.)

Anyway, the other day, while working in the garden, I noticed a somewhat large tan/white/brown ovalish growth (about 12" in diameter on the oblong bias). I went to dig it up and it immediately sent up brown "smoke" (which I'm guessing is it's spores being sent out elsewhere). I finally dug it up and got it in the trashcan with little disturbance. I noticed a similar growth on our fence, but am hesitant to do anything to that as it would definitly cause a release. Wetting it down didn't minimize the amount of release.

What could this growth be? Is there anything I could use (commercially or household) that would get rid of it?

Finally, do you think the funky smell and this growth are related?

Thanks for answering this somewhat targeted question.

Adrian Higgins: The mold is the exploding fruit of a puffball or possibly of the slime mold. They feed off organic matter and do not inhabit your fireplace. Your chimney may be home to some creature that may be dead or alive, or it may be allowing rainwater in that smells even if you think the chimney is dry. I would get a sweep to come and look at it.

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Alexandria, Va.: Adrian -
I'm submitting a day early because I won't be around live for your chat.

I have a couple of Tomato questions. I grew two varieties in my (very small) garden this year. Super Sweet 100 Cherry Tomatoes and Super Sonic (full size) Tomatoes.

As usual, the cherry tomatoes were as sweet as sugar. They were fantastic. The Super Sonics on the other hand, were fairly tasteless. In fact most of them tasted like supermarket tomatoes bought in January!

Is there a variety of full size tomatoes that tastes as sweet as the cherrys?

Also is there a variety that does well (or at least better) in a garden that doesn't get much direct sunlight?

Thanks!

P.S. Obviously, I'm thinking about next year.

Adrian Higgins: I harvested a melon the other day that by its color (a luscious yellow) and fragrance (powerful) suggested an ambrosial treat was in store. When I ate it, it was bland to say the least. I think all the moisture we have had this year has flushed all the flavor out of a lot of summer veggies. I am hoping for a drier one next year (never thought I would ever say that).

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Springfield, Va.: Adrian, I really enjoy all the good gardening information and thought I'd get your take on the following question. I have gotten so many conflicting answers (from garden centers, area State Extension Services, and gardeners themselves) -- what is the last frost date and the first frost date for our area? It is essential to know this in order to plan for the planting of seeds, transplants, etc. because one always has to count forward or backward from frost dates. Thanks again.

Adrian Higgins: Springfield: I am saying Oct 28th, 4 a.m. But seriously, the first frost is a peculiar thing in our region. It is possible and likely for gardeners in Leesburg to see a first killing frost in late October and you in Springfield won't get one until early November and my sheltered garden in Alexandria until mid November and some gardeners in Georgetown until late November. What often happens is that we get one degree of frost inside the Beltway while gardens outside get, say, three or four degrees, and that difference is the difference between a frost bitten landscape or not. You can also cover with newspapers or blankets or vegetable fabric things like basil or impatiens, and get them through the first frost and then wait under three weeks before a real freeze arrives and ends the show. So that first measure of frost protection can pay great dividends in extending the season into November.

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Washington, D.C.: Hi,

I recently moved into a new house. In the backyard are a couple of hydrangea bushes. Hydrangeas are my favorite, but I know nothing about gardening/plant care in general, let alone specifically about hydrangeas. Is there something I should do to the bushes now to ensure that they will bloom nicely in the spring/summer? For instance, there are dryish brownish blossoms still on the shrubs right now -- do I cut those off? Any help would be much appreciated.

Thank you very much.

Adrian Higgins: You are probably referring to mophead or lacecape hydrangeas, which do best in a site of rich soil with a little protection from the afternoon sun, and a location that is sheltered from the northerly wind in winter. This fall, make sure the shrub is well watered before the ground freezes, and give it a layer of mulch that will at leats protect its roots in its first vulnerable year. Remove the mulch to one inches in April. The biggest mistake people make is in pruning hydrangeas and thus remove the wood from which blooming wood will erupt next spring. Don't prune it, and leave the flowers, they are considered ornamental in their dried state.

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Reston, Va.: Thank you for all the information you give us every week! I had a question about replacing a redbud tree in my yard. It was very small when planted in the center of our shady front yard seven years ago but is now taller than the house and very skinny and bare in the middle. Basically it's just a thin trunk, two thin bare branches forking out, and then a canopy of the leaves, which are beautiful, but the shape of the tree is not very attractive. With no leaves in the middle it doesn't really hide our house from the street, and the top of it is drooping over our roof. I'd like to remove it this fall. Do you have a suggestion for a tree that would stay smaller and fuller than this redbud in these conditions?
Thank you.

Adrian Higgins: Any tree in too much shade will become elongated. I am wondering if an evergreen such as osmanthus or a taller holly or a viburnum named Chindo might work better for you. Otherwise I would go with an upright Japanese maple, which tend to stay dense. The redbud might have been helped by some formative pruning that would have encouraged some lower branching. Beautiful native tree, pity it didn't work for you.

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Columbia, Md.: Hello,
When would be a good time to prune my weeping japanese maple bush? It has grown so much. I am very hesitant to trim it for fear of harming it.
TIA!

Adrian Higgins: You could do a little trimming now, but wait until it goes into winter dormancy before doing any major pruning. This will be easier on the plant and on you-you will see the branch structure much more easily. Pruning a weeping maple takes a great deal of consideration, and experience is a boon. You remove entire branches, but larger ones should only be cut once you considered the plants from all angles. Don't remove more than say 20 to 25 percent of the mass of the tree in any one year. It is much better to cut too little than too much.

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Chapel Hill, N.C.: Azalea help, please! About seven years ago, we put in a bed of azaleas on the north side of our house (bright shade, but no direct sun). They were pretty neglected all these years: mulch and fertilizer, but the soil was not well prepared (dense clay) and I never pruned. They never flowered well, and virtually not at all this year. This summer it became apparent that there was only growth on the edges, and just bare branches on the interior. I took them out, and now have an empty bed. I love azaleas, and they provided great cover for the house's foundation. Is it worth trying again with better soil prep and pruning? If not, what else can I use that will cover the foundation adequately?

Adrian Higgins: Yes it is worth trying again, but don't buy cheap unnamed varieties. Find a nursery that has a good selection with named varieties. You then know the characteristics of the plant, not least its growth habit. Flower color is important and restraint is the order of the day. (No oranges with magentas, for example), but it is also important to consider the azalea for its leaf color, texture and size since this is the ornament that will carry the shrub for 11 months of the year. Before you replant, make sure you work the bed to give the azalea what it needs, a deep, rich, acidic soil that retains moisture without becoming waterlogged.

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Washington, D.C.: Adrian,

I'm the person who submitted the treebox/groundcover question earlier. Thanks for answering, but perhaps I should rephrase my question.

If not a groundcover per-se, can you recommend a complimentary perennial that can co-exist in a tulip bed, giving some interest when the tulips are gone for the season. Must admit I'm not a big fan of Liriope.

Thanks again

Adrian Higgins: Treeboxes are one of the worst environments for plants. Root run is constricted, moisture is scarce, the soil is dreadful, and plants must endure dust, pollution and feet. I was amazed once to discover that one of the biggest culprits for soil compaction in a city park was the pigoen. Every time they landed, they were compressing the soil.
So the options are limited. Perhaps Japanese garden junipers might work, though they do spread and need some room.

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Central, Va.: Help, please!

Our driveway is alongside a very unattractive side of our neighbor's house. We have about 7 feet from the edge of the driveway over to the property line & have planted shrubs - nandina, pieris, curly leaf ligustrum, rhodos, azaleas - and have a curly-needled white pine there. We've been waiting for them to grow and block the view.

Our neighbors are taking down a lovely tree - ash or linden, not sure what, that is on their side of the property line that helped block the view of the house & a shed & propane tanks. It has small but extremely fragrant blossoms; we mourn its loss.

Long story short, my husband wants to rip out all the plantings we have & put in Leylands. He wants to obstruct the view completely. I said, why not a privacy fence; he says we couldn't put in one high enough.

What would you do? My husband isn't even thinking cost (but I am), so go wild.

Thanks!!!

Adrian Higgins: Seven feet is quite narrow for tall plants. A clipped hedge would be a nice solution but that requires work, access to both sides of the hedge, and a lot of ongoing maintenance costs if you can find someone skilled enough to do it. Don't plant leyland cypress, they are too big unclipped, prone to a dieback disease in our climate, and are too dense and common. If, and this is a big if, if you were willing to fashion this as a large hedge, you could go with Southern magnolia. This would take five years to reach a good screening size, you would need to plant them far closer together than usual, perhaps just four or six feet, and then clip them each winter before the new growth erupts. They are also quite messy, you would have to endure the dropping leaves. But they are an extremely elegant plant and do lend themselves to clipping. Alternatively, consider unclipped stands of Japanese cedar, cryptomeria. A variety named Yoshino does well in our climate, others do not.

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Gaithersburg, Md.: As highly extolled as compost is by garden experts, why does no one ever suggest using composted dirt for house plants?

Also when is a good time to transplant Japanese anemones, and rose of sharon?

Adrian Higgins: You could use well rotted and well screened compost for your indoor pots. It is quite a bit of work to screen the compost fine enough for indoor use and is perhaps easier to buy bags that have been done for you.

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Germantown, Md.: Last week you mentioned "overseeding" a lawn that has weeds. I'd like to do that but am not exactly sure what that entails: is it just spreading grass seed over your existing lawn? Do you need to airate (spelling?) first? Thank you!

Adrian Higgins: Ideally, you aerate the soil prior to seeding. Seed needs contact with soil to germinate, so if you don't aerate you should either rough it up by dethatching or using lots of organic stuff like peat moss or compost on top of the existing lawn before seeding. Best of all, you dethatch, aerate and then top dress with compos before reseeding. We are out of time, but one last point: Grass seed doesn't need irrigating with vast amounts of water: It needs continuous moisture, a spraying in the morning and at night. Only when the grass is growing does it need sufficient moisture to get established. Same time next week.

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