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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Anonymous: Home of the wash. baseball club! ola! Bought a nice mum for me mum... if I leave it in the pot can I still plant it later this fall? Can you suggest a good groundcover for a veg. bed? I did rye last year -- never again, it was very hard to till. Thanks

Adrian Higgins: I find red clover to be a good winter cover crop, I have not tried hairy vetch, which is also popular. I have had no problem digging in winter rye. Must be me muscles. Maybe I should offer my services to the Washington Expos. I am lobbying for a new name that reflects the gardening world: The Washington Composters.

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Keedysville, Md.: Is it okay to mulch now in the Fall? I didn't mulch in the Spring.

Adrian Higgins: Mulching would be fine now, it certainly would make the beds look neat as the herbaceous plants crawl back into the ground. Do make sure that you mulch to a level no more than two inches deep and that you avoid heavy doughnuts of mulch against a tree trunk.

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Silver Spring, Md.: Dear Adrian: First, what wonderful weather for planting, yes? Though this may be really a landscape question, I thought with your eye and years of experience you could advize: My front yard slopes steeply up to the home. To minimize the slope's appearance, what do you think of teracing the lower part and planting ornimental grass, lirope, and other mostly non-flowering plants -- playing with greens and creating hight. I have plantings on the side of my house, so the lawn would now only be in the center. What do you think? Thanks so much.

Adrian Higgins: As a rule any plant that cascades will hide the contours of the ground. I think at the moment of beauty berry because of its arching branches filled with cluster of intensely purple fruit. Cotoneaster, hakone grass, pennisetums, and even dwarf nandinas would be effective.

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Roanoke, Va.: I know the preferred time to move plants is in the fall. Does this apply to rhubarb plants and peony bushes, or should I wait for spring? Thanks for your ever helpful advice.

Adrian Higgins: Peony certainly can be divided and moved now. I have only managed to kill rhubarb in my hot humid climate, I would think, though, that if you were to move it, now would be better than in the spring for the sake of the roots.

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Carpet of Pine needles: We have a 100 year old house and what looks to be a 100 year old pine tree in front. We love it, it's about the height of the house, but this past week the small spot of ground around the tree is coated with a carpet of needles. Is my tree not much longer for this world? I don't remember it doing this last year and I hate to lose it.

Adrian Higgins: It may be the natural dropping of the older leaf needles. If may not, though. If entire needle bundles are dropping you may want to call an arborist to take a look.

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Dublin, Va.: Do you know of an on-line source that sells the Narragansett crabapple tree? I've tried forestfarm.com but they don't have them at the moment. Thanks.

Adrian Higgins: I've been looking, but to no avail. I would call the National Arboretum and ask them if they have a list since it is one of their introductions.

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Washington, D.C.: Hello,

We just moved into a house in NW DC. The previous owners left us with two beautiful trumpet vines growing on a pergola in the backyard. We have been told we must cut back these vines "to the wood" but are unsure to what degree or at what degree. When during the fall/winter should we do this pruning (after the first frost? before the sap rises?) and how far back do we cut? All the way to the larger woody main vines or just back to the light brown sections?

Thanks very much.

Patricia

Adrian Higgins: They do get rangey and benefit from shaping. This flowers on new growth and as a rule you would cut it back in winter dormancy.

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Glover Park, Washington, D.C.: Adrian:

I've ordered 24 Irish Moss plants to put on a steep, rocky hillside that gets some sun, but not alot. Is this endeavor likely to succeed? Anything I can do it improve its chances?

Adrian Higgins: Irish moss, which is not a true moss, looks great but is difficult to establish in our climate. Give it good soil but good drainage, and try to water the roots rather than the foliage, if possible.

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Alexandria, Va.: Is it too early to plant daffodil & tulip bulbs? This weekend? next weekend? Or, should it be chillier weather?

I've got bulbs that did NOT get in last Fall (due to the rains we had, every weekend, it seemed). Are they worth planting?

Adrian Higgins: Use last year's bulbs as missiles to throw at squirrels. They are of no use for anything else. Given the procrastrination, I would recommend putting in this year's bulbs immediately, if not sooner.

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Takoma Park, Md.: I started clearing out the beds last week. Put in some mums to take up the void left from the sunflowers. Anything else for some fall snap?

Oh, and what to do about black eyed susans, they are really spreading. Should I pull them now or pull chutes in the spring?

Adrian Higgins: Mums are the obvious choice beacuse they are plentiful and in bloom. Filling gaps takes a bit of foresight and planning. Go to a botanical garden in our area, Brookside Gardens, for example, and you will see such late season annuals as coleus, Mexican bush sage, cannas and other plants carrying the load of the late season, but all of them were planted as small plants in early summer. You might find some ornamental grasses in pots to stick in places.

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Herndon, Va.: How do I locate a reliable arborist? I have an oak near the house which may have oak wilt. It almost certainly has to come down, and steps will need to be taken to protect other oaks in our wooded back yard (adjacent to parkland). However, we have not had much success differentiating between legitimate arborists and people who see our high priced neighborhood and quote outrageous prices.

Adrian Higgins: I would think as a minimum you want someone with proof of insurance and bonding. I am reminded of the tale of the tree guy a couple of years back in Northern Virginia who was felling a tree that went the wrong way, fell on a house. He then said that he was going to get help. He must still be looking becase he never came back. A magazine called Washington Consumer Checkbook did a piece on arborists a while ago. See if they have that available in their archives.

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Frederick, Md.: Hello Adrian! Next spring (or this fall) I want to plant some tall grass in large pots to sit on one side of my deck for a bit of privacy. What type of perennial grass would work nicely? I've heard of pompus grass, but are others that would work well? Thanks!

Adrian Higgins: It's actually pampas grass, and is quite self effacing. It is marginally hardy in Frederick, and I would go instead with maybe a tall miscanthus. I am growing a cultivar named November Sunset that is a stupendous garden plant.

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Alexandria, Va.: Help! We had to transplant a kwanzan cherry tree (about 7 feet tall) a few days ago. We left the root ball as big as we could and watered after planting. But, the leaves are turning brown. Is that due to the stress of moving it? Will it come back next spring? Love your chats!

Adrian Higgins: It is probably responding to the stress of moving. Make sure that it is well watered in in its new location (though I think the storm named Jeanne may have done the trick). It should not, however, be overwatered and it is important that the crown of the rootball be set an inch or two above the soil line for proper feeder root drainage. If it is set too deeply, dig it up and raise it up a bit, even if that is a chore.

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Anonymous: When can we start pruning? Novice gardener here and inheritor of a nice townhouse garden. Our crape myrtle is going out of control and rose of sharon needs a cut not to mention the japanese holly, hostas; they're taking over our back yard. Are we supposed to wait until a frost, dormancy? My hands are itching to get a hold of pruners!

Adrian Higgins: I would definitely wait for winter dormancy for the crape myrtle, and also the rose of sharon, come to think of it, because it its deciduous state, it will be far easier to see which branches should be pruned. Don't shear either shrub, simply remove whole branches to improve the shape and bring in light and air. Do this conservatively, better to take off too little than too much. The perennials can be chopped back now or lifted and divided if they are too crowded.

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Annandale, Va.: Adrian,

I have a very large, healthy red oak that sits at the top of a hill in my yard. In the last few years a patch of the hill about 10 feet from the base of the trunk has eroded next to my driveway, exposing some roots. I'm probably going to build a small retaining wall to stave off the erosion, but I want to know if I can sever 3-4 roots that are about 1" in diameter or less without harming the tree. Again, these roots are at least 10 feet from the tree.

Thanks!

Adrian Higgins: Yes, that should be all right. But do the tree a big favor by giving it a light mulch of compost, keeping its root zone away from lawn chemicals, and replacing the soil where it has washed away.

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Purcellville, Va.: I incorporated six pick-up loads of mulch into my clay-heavy garden this spring, yet the soil is still hard-packed and it does not drain at all. Even after a Summer, the beans I planted in early September grew poorly. Is there any amendment that can be added to poorly drained clay soil to improve its texture?

Adrian Higgins: Apparently so, it is called PermaTill and is a mineral that lightens heavy soil and, unlike organic matter, doesn't rot away. Gardening friends swear by it, I haven't used it yet. I believe the website if permatill.com.

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Alexandria, Va.: I am trying to establish a living fence between my property and my neighbors property (the area is underneath a large maple, so it is shady). I am thinking a multi-layered approach is best. I have a few aborvitae planted (although some died), but what other types of evergreens can I plant? Will hollies work? Please help as they added on an addition and being in my yard feels as if I am really in their backyard!

Adrian Higgins: It is difficult to grow anything close to a maple, which casts dense shade and has lots of surface roots. You may want to consider taking down the maple and then planting a hedge of evergreens, but not Leyland cypress or hemlocks . I like cultivars of Eastern red cedar, which are underused and beautiful.

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Fairfax, Va.: What plants and shrubs do you recommend for an area that gets morning shade and afternoon sun? I am trying to landscape my backyard. Thanks!

Adrian Higgins: The world is your oyster. You have a site that is in full sun so anything that can take full sun will work. Most people struggle with too much shade, and their craving for flowers is never satisfied as a result.

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Hollywood, Md.: Will ivy covering a very large old oak tree be detrimental to the tree??

Adrian Higgins: Perhaps only in its competition for soil nutrients, not for strangling the tree. I don't like to see mature ivy vines smothering a tree purely for aesthestic reasons. It hides the silhouette of the tree.

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Olney, Md.: Please help a clueless homeowner that sits evryday in the blinding sun!

I want to plant a good shade tree approximately 25 feet from my house and 10 feet from my concrete patio that will provide nice shade from the afternnon sun. Do you have 1-2 suggestions? When is the best time to plant? Thanks much!

Adrian Higgins: The biggest mistake is that people select trees that will become too large for a small backyard and plant it too close to the house or patio. When it becomes evident it is outgrowing the space, it is too big to move. I applaud your insight. I would love for you to plant a white oak, which is a tree for the ages and would be sufficiently upright for its first couple of hundred years to work in your space. A smaller candidate might be a littleleaf linden or even a buckeye tree.

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Hard Work for Naught?: This year I had huge problems with rabbits, squirrels, and even rats (Arlington's dirty little secret) eating my sunflowers, squash and some tomatoes. I had good luck with peppers, eggplant, herbs, and many cutting flowers. Barriers didn't work to keep the critters out.

The few tomatoes I got were pitiful; most of them were scrawny and didn't ripen. What can I add to my garden now to ensure I have a better garden next year? Last winter I added good compost, humus, and a winter rye cover crop. PS - Please give me non-chemical suggestions. Thanks for any wisdom you can share.

Adrian Higgins: I have had some serious setbacks myself. I wonder if you should take a year off from tomatoes and sunflowers and go for leafy greens and stay with your other stuff. OUr vegetable garden columnist, Barbara Damrosch, is one of the best in the business, so keep an eye on what she suggests.

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Annandale, Va: Hi Adrian,
Thank-you for taking my question. I have a 15 - 17 years old pony tail plant about 18-20" high. I saw in the store a pony tail cut at the top, and there're several new shots on the side.
I'm just wondered ... can I cut off the top of my pony tail plant, and its new shots will come out like the one in the store ?
I always pinch my plants to get they grown more bushier. So I thought the same theory apply.
Please tell me before I "gullotined" my plant. Thank-you.

Adrian Higgins: Is that a lycopod? I wouldn't prune it at all, if so. Does anyone else have ideas?

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Columbia, Md.: Greetings Adrian,
I need to move a couple of peonies, and have heard that fall is the best time to do so. Do I cut the foliage off, or leave it? Thanks so much for your help.

Adrian Higgins: trim off the foliage after you have dug and examined the plant. You should be able to see next year's buds in the crown, which should be planted one to two inches below soil level, deeper than with other perennials.

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Alexnandria, Va.: We just bought our 1950s cape cod last year and it does not have a single tree in the front yard - nada. I'd like to plant something to break up the expanse of grass. Something ornamental b/c I don't want it to take over the yard. Any suggestions? It faces south east so there is plenty of sun.

Adrian Higgins: Perhaps a Sophora japonica. A tough tree which might endure the awkward co-existence with the lawn. Trees and turf as a rule have different cultural requirements.

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Spencerville, Md.: In April, I planted three Arabis 'Alpina Snowcap' plants along with a variety of other perennials in an area that gets full sun in the morning to mid-afternoon. While the plants have done well initially (and the rest of the perennials I've planted), they are now dying. One plant died very quickly, within a week in August. Now I have a second one that is struggling, and the third looks okay but has a few yellowing leaves. The leaves' edges wither and turn brown. The browning and drying out continues inward until the entire leaf is affected. I checked for insects and didn't find any. I applied powdered sulfur to the remaining two plants after the first death, thinking it might be a fungal disease. Is there something else I should consider?
Thank you!

Adrian Higgins: Arabis are rock garden plants for poor, dry and chalky soils, not a good candidate for a mid atlantic clay garden. If you can provide extremely free draining soil with no organic mulch, you might have luck.

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Germantonw, Md.: Hello Adrian

I have some impatiens, which I grew from seeds, that are infected with some type of fungal disease, which has spreaded throughout my garden. Until recently, they were looking pretty healthy in my garden as well as in my containers. Since I've never experienced this type of problem when I purchased impatiens from a nursery/Lowes/Home Depot, I'm wondering if I did something wrong while they were seedlings (i.e., too much moisture, etc). Or is it because we had such a wet summer? Also, what should I do about the soil and containers which have the infected plants? should I get rid of the soil in the containers which have the infected impatiens and clean the containers with bleach? (By the way, I've been using Ortho Disease Control to keep the fungus under control. It seems to help).
Thanks for your help.

Adrian Higgins: You may have selected a variety ill suited to our hot humid climate, or if this was seed from a hybrid you grew, it will not grow back true. Next spring, buy seedlings that have been prepared for this region.

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Reston, Va: When's the best time to plant boxwoods? Now, or should I wait until spring?

Adrian Higgins: Now is a great time to plant boxwoods or any other shrub or tree. The soil is warm and a new plant will soon set roots before the winter freeze. This will diminish the risk of frost heaving of the rootball, which is disastrous because the feeder roots desiccate when exposed to air.

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Bethesda, Md.: Thank you for this informative chat! Would you be willing to provide a quick "to-do" list outlining how homeowners should prepare their lawns and gardens for the colder months, ie., mulch in October; prune in November, etc. Thanks in advance from a newbie gardener.

Adrian Higgins: Lawn renovation should be completed soon, so that the seedlings are established before freezing. You also want the seedlings to be well up before the leaf drop in about a month, becuase you have to remove the fallen leaves to prevent matting of the new grass.

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Leesburg, Va.: Adrian -- I know it's not the season, but I want to get ready for next summer. Which perennials can be cut back as they are growing in early summer so that once they bloom they won't be so tall that they fall over. Sedum? Joe pie (sp?) weed? Summer phlox? Butterfly bush? Others??

Adrian Higgins: All those things, complete your trimming by early June.

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Baltimore, Md.: First of all, I recently came across your Mid-Atlantic book and I really enjoy it.
I'd like to plant a small magnolia tree in my small yard. 1, do i plant it soon, and 2, how far away from any retaining walls should it be planted? I haven't seen anything on the root structure.
Also, I'd like a witch hazel plant (on your recommendation). Can they be planted in the fall?
Thanks so much.

Adrian Higgins: Small magnolias become large ones, I would allow at least 10 feet from your wall. Witch hazels can be planted now, preferably, or at other times. Magnolias have fleshy roots and are best planted in the spring. If you are careful to minimize root damage you might try now. Alas, we are out of time. See you in the cybergarden next week.

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