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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Middletown, Md.: Adrian,
Can Coreopsis be divided? We have a clump that is beautiful but getting very large and I would like to use it to fill in some empty spots in the flower bed.

Adrian Higgins: Absolutely, but some varieties also grow tall and either need staking or should be cut back when the growth first reaches about four inches in May. This will produce a stouter perennial. When dividing, lift the whole plant and then separate divisions. You are looking for pieces that contain young, fresh areas of the crown and with root systems intact.

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Alexandria, Va.: Adrian, is this a suitable time of year to prune my nice healthy redtips? They do indeed have red tips right now as they've been having their late-summer growth spurt. I'd like to shape them a little but don't want to stimulate tender new growth by pruning just as they're starting to feel sleepy for dormancy. Same question for my large American holly: can I shape it a bit at this time of year? Thanks.

Adrian Higgins: I would be much more inclined to clip the holly but not the photinia, which, as you say, will result in new and tender growth. The photinia is more susceptible to frost damage than the holly. Better to prune it in May or early July.

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Arlington, Va.: Adrian, that's quite an ad for cellulite cream at the top of my screen right now! Three bikini-clad derriers. I knew gardening was fun, but woo-hoo!

Adrian Higgins: Those are my watering maidens, they accompany me through the garden. It's in my contract.

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Getting crowded: Greetings! Quickie: is it now OK to thin day lilies? Oh, yes, one other: what are the long-lasting, heavily flowered, woody, bush-type trees planted all over suburban areas? Magenta flowers, mainly. thanks!

Adrian Higgins: I think the latter is the crepe myrtle, in all its forms. Now is a good time to thin daylilies. See instructions above on dividing perennials.

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Washington, D.C.: I put in three monarda this spring and they have grown lush and full -- but no flowers. Zip. Is this typical for the first year, or am I doing something wrong? They get full sun, growing in pretty well-drained D.C. clay enriched with compost and manure, planted next to some rudbeckia.

Adrian Higgins: They should bloom in the first year, though weakly. Possibly the soil is so rich it has induced vegetative growth at the expense of flowers. I would not fertilize them and see how they do next year. Certainly don't give up on them.

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Alexandria, Va.: Hello!

I have a lot of Iris that did not bloom this year -- plants look healthy -- just no blooms. Others in the same spot bloomed well (but all the ones that bloomed were the same type of small, dark blue/purple).

What should I do to ensure that they ALL bloom next year.

Thanks!

Adrian Higgins: If they are bearded iris, it may be that they need dividing.

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Maryland: Can a large holly tree grown out of control be re-shaped? It's about 20 feet high and looks out of balance.

Adrian Higgins: To a degree. Old hollies are harder to regenerate than younger ones. I would not advise cutting it back to a hat stand. You could do some shaping.

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Alexandria, Va.: Mystery Plant
I can't tell you how helpful I find your chat -- thank you! I moved into my house last fall. This summer, in one of my azalea beds, a plant emerged that wasn't there before. It has several "branches" that have grown about 2 - 3 feet tall. It has leaves and flowers that look like those on crepe myrtles (it's flowering now). There aren't any crepe myrtles within 40 feet of this bed, and the plant wasn't there last year. Do you have any idea what it might be? I realize you aren't telepathic, but I thought you might know. Thank you for your help.

Adrian Higgins: It might well be a crape myrtle seedling desposited by a bird.

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Silver Spring, Md.: I have a potted Mock Orange that I'm waiting to plant. I've noticed that it has developed a white "coating" that appears sort of fuzzy halfway up the main stem. I've scraped this off, but it's grown back. What is it and howdo I get rid of it (if it's hurting the plant) Also, what's the best time to plant it? Thanks for your help! Love the chats!

Adrian Higgins: This is powdery mildew, I suspect, exacerbated by another damp and cloudy summer season. You can move hte shrub to a brighter spot with better air circulation.

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Virginia: My lawn and many lawns in the neighborhood have these odd holes in them, surrounded by mounds of dirt. The holes are approximately 1 inch in diameter, and the dirt surrounding them is very plentiful! I thought this might be some sort of rodent, but I actually saw what I believe is the creature who created these holes, and it looked like a large, very colourful version of the Brood X cicadas we had a few months ago. It flew directly into one of the holes, so I assume it was the one who created the whole.

What are these things? Different cicadas?

Fascinating!

Adrian Higgins: I don't think these are cicadas, they might be cicada killers, which are wasps that drag cicadas into their holes. You might have seen a luckless victim and assumed it was entering under it own steam.

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Washington D.C.: It's my first garden with lots of shade. The summer's impatiens and various green plants have done really well. What might I plant for fall that will keep the garden going? I'd like some color before winter sets in.

Adrian Higgins: There are hostas that bloom late, including one called Hosta tardiflora. I would also plant Japanese anemones and hardy begonias, for show in future years.

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Rockville, Md.: Hi Adrian, A few months ago I replanted an indoor house plant before a long move. I used to keep it by a window with the shades either open or shut in a house with no air conditioning. My new apartment has A/C (not sure if the air makes a difference). The plant (I'm sorry, I don't know the name) is drooping, yellowing, etc. I also think the soil (Miracle Gro) is always too dry. Still, I water it about twice a week and try not to give it too much sun. The plant has tall, spindly stalks and large leaves. It's not completely unhealthy because there is new growth. Any suggestions to make it healthy again? I've recently moved it a few feet from a window (I close the shade slightly and leave the window open).

Adrian Higgins: You are probably overwatering it. Repot it, examine the roots, and give it a larger pot with fresh soil. Give it a watering and then hold off until the top of the soil is nice and dry. It would help, of course, if you could identify the plant.

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Ft. Washington, Md.: Dear Mr. Higgins:

I am a true novice about trees and plants. I moved into my house in January and the previous owner had in the front yard a beautiful laceleaf weeping Japanese Maple (found out from the internet). However, lately the leaves are a strange color, no longer red, maybe a mixture between red and green and the branches have white spots on them as do some of the leaves. Around the tree are begonias and azalea bushes in case it's important to know that. Is this some type of fungus, is the tree sick (for lack of a better word), is there anything I can do to make it better?

Thank you for your time.

Adrian Higgins: The heat will render a lot of purple leafed maples an olive green in summer. The white spots may be a scale insect, which need to be physically removed and killed, but don't damage the bark as you do it.

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Arlington, Va.: Our lawn has a lot of weeds such as dandelions, crabgrass and moss. There are also several areas that need to be reseeded. What should we do first and when? Should we use a weed killer first, then reseed. And should we fertilize in the fall? Thanks.

Adrian Higgins: If the lawn is more than half weeds, then it is better to wipe out the whole monstrosity and start again. You want to address the reasons the lawn is in bad shape in fixing it and this can only be done properly with a soil test. You can get a kit from the arlington county extension office. I would spray the area with Round Up in the next week or so, wait another week or so, and then cultivate the soil, add lots of amendments such as peat moss and bags of compost, and then, after raking and smoothing, sow fresh grass seed. A thin layer of straw will help keep the seedbed moist and discourage birds.

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Columbia, Md.: Is it safe to plant China Boy/Girl Holly and move around some eonymus right now? Can I plant flowering perennials this fall for the spring?

Adrian Higgins: Absolutely, now is a great time to be renovating and planting ahead.

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Mount Pleasant, Washington, D.C.: Adrian,

I have a small plot where I planted a large amount of corn, basil and pole beans this year. All have done well and were delicious -- the corn is done as is the basil but I'm still getting about a quart of beans a day. I was hoping to plant lettuce, etc. but didn't want to take my beans down prematurely -- how much longer should I expect the beans to produce?

Adrian Higgins: If you take the pods when they are young, the beans will be encouraged to set more. If you want the beans to stop, you should let the pods develop fully and perhaps allow them to dry for winter use. You can sow lettuce as late as early September and still get a good fall crop.

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Annandale, Va.: Hi Adrian,

This is not about plants, but I hope you can help me out...
In my garden, and patio, front porch, I've noticed that large insects look exactly like mosquito, but much much larger than the regular mosquitoes. Some of them, with their legs spread out are as big as my palms. What are they? And do they bite like mosquitoes? I can't go out in my backyard anymore because of these "creatures." Thank you for any light you can shed on this.

Adrian Higgins: There are large, mosquito like insects that are not mosquitoes or blood sucking. Sit near them and if they start biting, you will have your answer. Better yet, ask the neighbors over and give them a tall glass of lemonade and see if they draw the bugs. Perhaps you can stay in the kitchen with a pair of binoculars.

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Arlington, Va.: Our large crepe myrtle bloomed very well this year, and the blossoms lasted a very long time. However, now I am noticing that some of the faded blossoms/spent buds are covered with a white fuzzy substance that looks like mold or mildew. What is this, and should I be concerned?

Thanks, really appreciate the chat.

Adrian Higgins: This is powdrey mildew. When planting a new crape myrtle, it is important to choose varieties bred for resistance to this disease.

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Salem, Va.: I shoulda done better in siting my asparagus patch two years ago.... and now I need to move it. Should I do so this fall or wait until spring? Thanks -- I'm planning my fall "moving" schedule.

Adrian Higgins: Move them now, but try to minimize root damage. Lift them with a gardening fork. They will settle in for the fall and regrow feeder roots, and shouldn't miss a beat for the spring harvest. I assume you put them in too shady a spot.

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Centreville, Va.: Hi, Adrian! I've got these weird pine cone thingies springing up all over my yard in inappropriate places, including deciduous trees and fences. What the heck are they? What should I do with them? How is my tree doing this??

Adrian Higgins: These are bagworm cocoons and you need to pick them off and throw them in a sealed bag.

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Alexandria, Va.: Good morning, Adrian!

I noticed that my patch of Hakonecholoa Grass has suddenly (mostly) dried up, as if it is already going into its dorment phase. This is my first year of trying to grow this plant -- is this normal for late August? Or should I plan to invest in some replacement grasses this fall? Thanks for the advice.

Adrian Higgins: This grass needs consistently moist soil and some shade to flourish. It shouldn't be drying up now. In late summer, it does produce its flowers, wispy things on stalks, which might be mistaken for dried leaves.

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Annandale, Va.: I'd like to bring in an hibiscus plant for the cold months, but in the past when I've done this, plants have lost their leaves by the droves over the winter. Is there a certain way to care for them till they can go out again in the spring?

Adrian Higgins: It needs a cool, moist environment. A sun room perhaps that is barely heated and with lots of plants and watering to keep humidity levels high.

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Arlington, Va.: Hi Adrian, We are hiring a landscape designer to create a "master plan" for our suburban yard. We meet our first candidate today.

Our goal is to have a plan that is low-maintenance with native plants that would work with a dog and small child.

Any words of advice? Questions we should ask? Thanks!

Adrian Higgins: Plants that are low maintenance, i.e. grow within bounds, survive drought and flood, and don't get pests and diseases are not that common. It is possible to build a landscape with such plants, though often you forego colorful blooming or handsome foliage. It is important to understand that when plants are young and have small root systems, it is imperative that you look after them, and this goes for low maintenance plants as well. You do this by giving them good soil conditions, keeping them watered as needed, and mulching to help with winter hardiness until established.

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Mount Pleasant, Washington, D.C.: I have a terraced front yard, with typical heavy D.C. clay throughout. This spring, I dug up and enriched the middle tier and planted it from scratch, but now I need to tackle the lower tier. It is full of daylilies, moss phlox, astilbe, hosta, ferns and lungwort. Should I plan to dig up each and improve the soil all around, or will a top-dressing be enough? If I need to lift, when is the best time? The phlox and hosta seem oblivious to the clay, but the daylilies and astilbe are definitely unhappy.

Adrian Higgins: I would either do the whole bed, or just the daylilies and astibles.
Alternatively, you can lay a mulch of shredded leaves twice a year. This will greatly improve the quality of the soil if you are religious about this and are willing to wait two or three years for the microbes and worms to do their work.

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Alexandria, Va.: Is it too late to have a large silver maple trimmed (fairly substantially), or should it be done earlier in summer when there is more time for the wounds to heal? Thanks as always.

Adrian Higgins: Large tree wounds may take a couple of years or more to callus properly, so now is as good a time as any. If it were a more precious tree, I think I might wait until winter dormancy at this point. But with a silver maple, you could trim it now (or get a professinal to do it, tree work is exceedingly dangerous).

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Reston, Va.: We planted a few Knock Out roses last year and I have to admit they are a beautiful addition to my low maintenance front yard. But, they have nearly quadrupled in size and starting to look a bit out of control. Do I need to prune or trim these shrubs? And if so, when is the best time of year? They really do produce a remarkable amount of flowers and are low maintenance except for having to spray them to keep the Japanese beetles away! Thanks!

Adrian Higgins: That's interesting because mine have not been troubled by Japanese beetles. In maturity, and with proper late winter cut back, they will get to be no more than four feet by fout feet, which for a rose is nothing. Just make sure that you are doing your annual March pruning to leave four or five healthy canes at about 20 inches.

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Silver Spring, Md.: I'm trying to find something "new" to replace the dying out petunias in my hanging baskets. Got any ideas besides mums? I've got mums all around in pots on the ground -- so I'd love to do something different that will last into late fall. Thanks!

Adrian Higgins: Maybe some Dragon Wings begonias, if you can find them.

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Arlington, Va.: I have a pretty extensive container garden right now. As a container garden, it's seemed best to stick to annuals. However, I had some toad lilies live through last winter in a pot, so I bought some more perennials this spring to see what would happen. Of course, a number of perennials don't bloom in their first transplant year and a lot of these were spring-bloomers, so... not much happened. In a normal (i.e., in-ground) situation, I would buy perennials in the fall to help them establish. However, I am worried that if I start putting perennials in pots this fall, their roots will freeze and I will have nothing. I have mostly shade, and it seems like most of the shade things I want to plant are not annuals. Should I stick it out and see what happens to the current perennial tenants (lamium, anemones, violets, clethroides, aforementioned tricyrtis, ferns) over this winter, or should I keep experimenting?

In hindsight, I guess some good bog plants would have worked this summer. Skunk cabbage on the patio, though -- no.

Adrian Higgins: I would plant perennials in pots and then simply sink the pots into a spare corner of garden bed over the winter to protect the roots. Bring them back out in March.

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Wild Acre in Marriottsville: We are experiencing some bagworms (or are they tent worms) that have made a net on a few of our trees, particularly a semi-mature mulberry that we want to keep, and a black locust that we are tolerating (they are prolific here)

What to do? I recall something on burning, but not much.

The person with mayflies on their porch may have a heart attack while looking at those bugs with binoculars! They are harmless (and hapless fliers). Mosquitos are not.

Adrian Higgins: These are fall webworms, which should be removed when the webs are small, as are the caterpillars. You could spray with Bt, but you still have the unsightly mess of the web. If you can reach them, cut them out from their little branches (the tree can afford to lose a few twigs) and place them in a sealed plasic bag. Assuming you can reach them safely.

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Arlington, Va.: My lawn is being overtaken by a combination of weeds -- clover, oxalis, ground ivy, wild strawberries. Pulling them out only seems to encourage more growth. What do you suggest?

Adrian Higgins: See earlier response on renovating a weedy lawn. This is the time of year.

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Arlington, Va.: My small patch of sweet woodruff has turned gray on the stems and lower leaves. Is a fungus to blame? Should I tear out all the plants and put in something else next spring?

Adrian Higgins: it's a mold disease. Leave it, the plant looks scruffy at this time of year anyway, but will come back afresh in the spring. If you can't stand to look at it, you might cut back the worst of it.

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Reston, Va.: Adrian --

I have a 20 year old cherry tree with blight in my front yard. I will cut it down this winter (don't like it anyway) but my home owners association will require that I plant another tree in its stead. I will be required to plant something similar -- basically an ornamental flowering tree, though I am going to try to convince them that it should be smaller than a cherry.

Can you suggest a nice, small, flowering garden tree for this spot. I also have several tall, stunning crepe myrtles in that area, and I don't really want another.

I want something that won't be subject to the same blight from any blight residuals in the soil. I was thinking a dogwood (I'd love Virginia, but I'm concerned about disease for that or one of the Asian varieties.) Do you have other suggestions?

Thanks.

Adrian Higgins: I would not plant a dogwood in such a stressful site. I would go with an improved crab apple variety such as Naragansett, or possibly a redbud.

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Bowie, Md.: Perhaps the large mosquitoes are actually what my dad calls "mosquito hawks?" They are harmless, and more than likely hungry for the smaller, biting mosquitoes. We have quite a few of them -- and not nearly as many of the smaller biting mosquitoes we had last year.

Adrian Higgins: Thank you.

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Arlington, Va.: I really enjoy these chats! I just dug up a lot of pacasandra (sp?) that grew up to the edge of my house. I don't want this area to be hospitable for mice and critters, so the 6 - 8 inches of foliage is gone. Do you have any suggestions for a (very) low-growing ground cover that does well in shade? The area is four feet by two feet.

Thanks!

Adrian Higgins: Most shade plants by nature have larger foliage to gather as much sunlight as possible. I would go with gingers, asarum, and perhaps some mondo grass.

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Washington, D.C.: There is a small patch of land where two alley's come together at the end of our block, visible from the street. Someone used to garden in it and there are some larger bushes, tons of bulbs, and other plantings. But, the kudzu and trees of heaven just take over. I'm not sure if the tree name is right but they grow all over, and spread underground, and have a straight stalk. While a few people will clear out trash from time to time, no one really has the time or inclination to keep up with it. Is there something, short of digging it all up, that can be done to control the weeds? Some of us do cut back the bushes, and otherwise it would be attractive.

Adrian Higgins: No, weeds will appear if you don't weed. If you commit to 20 or 30 minutes once a week, I think in time you will have the bed back to where it should be. Mulching will also keep the weeds down.

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Phoenix, Md.: Hi, I have some Black-eyed Susans in a pot and would like to transplant them to a spot in my yard. Two questions -- the stems of the flowers have a little black bug on them (flea size, but does not jump). What are these and what should I do about them? Second, when should I transplant the flowers?

Thanks for your help!

Adrian Higgins: I don't know what the insect is, but spraying with water may dislodge them. Black eyed Susans will grow in poor soil but they are happiest in rich soil, where they will seed and keep coming back, to the point that the seedlings need thinning each fall. A wee bit of afternoon shade wouldn't do any harm either, they do wilt in strong sunlight.

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Alexandria, Va.: I have a few plants (geranium, mandevilla, etc.) that I'd like to bring in over the winter (my mom has done this for years). Problem is that I have the worlds smallest house -- no room for big pots of flowers. Could they overwinter in a protected shed, or is there some quick greenhouse type box I could construct to shelter these plants?

Adrian Higgins: I think these would overwinter in a protected shed. I would cut back the mandevillas, give them a watering and mulch and place them in a black trash can and pile some leaves over the roots and crown.

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Arlington, Va.: I'm the container gardener. I don't have a corner of the yard -- I am in an apartment with a very large patio. I guess the answer, then, is plant and hope?

Adrian Higgins: Yes, I think the perennials probably will overwinter in pots, but try to provide some shelter for them, either by grouping the pots together or placing them against an east or south facing wall.

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U Street & 13th (Washington, D.C.): I purchased a croton about two months ago. I purchased it because of its beautiful dark leaves splattered with bright reds, oranges, and yellows. I never knew it would be so hard to care for.

After a week, these white cottony spongy formations formed on the stems, which I later learned were some sort of infestation of mites or spider mites. I bought some plant herbicide and and then cleaned the leaves with mild soap and water.

Then the leaves started to droop. It was a sad sight. I was feeling like I was losing a friend. I didn't know what I was doing wrong. Then I found a Web site devoted to Crotons and learned that I was under-watering... and as soon as I watered the plant -- given 3 hours -- the leaves perked up. It was amazing.

However, the plant doesn't have the same luster that it had at the nursery I purchased it from. It has new green leaves sprouting, which I feel is good. Do you think I should leave it outside on my balcony? I don't have a garden. I live in buidling in D.C. Do you think I should just leave it outside all day on the balcony and bring it in at night? The window it sits on gets moderate light but not direct sunlight.

What do you recommend?

Adrian Higgins: Last reply, I'm afraid. Crotons are not hardy so you will have to bring it indoors in October. This will undoubtedly stress the plant but you can condition it for indoor life by bringing it in every night in the two weeks leading up to its confinement. In the nursery, plants are made highly attractive through leaf dusting and polishing and grooming, as well as growth chemicals applied during greenhouse production. It's like buying a car, it will never quite be as good looking as when it sat in the showroom. But striving for it is half the fun. Same time next week, thanks.

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