The Garden Plot

Gardening

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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Washington, D.C.: Hi Adrian, we've had a sudden emergence of what we think are moles in our yard -- raised areas of turf that are very soft when you walk on them. Tunnels? What is the best means of getting rid of them? Thanks.

Adrian Higgins: These are moles. The most effective method is a mole trap, available from better hardware stores.

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Arlington, Va.: I planted caladiums for the first time this year. When and how do I dig them up and store them over the winter?

Adrian Higgins: You should probably lift them now, put the bulbs out in the sun to cure for a while, and snip off the top growth. Store inside in a well ventilated, cool room.

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Washington, D.C.: Okay, I have just gotten my bulbs. What is your best advice for keeping the critters away? Thanks very much!

Adrian Higgins: If you mean keeping squirrels from lifting them, the standard advice is to put one inch poultry wire above the plantings. This can be hidden with a layer of mulch.

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Arlington, Va.: I'd like to replace a mature, but underperforming, lilac bush this fall with something that provides more than just spring seasonal interest. Can Fotherfilla take full sun? If not, other ideas for non-evergreen large bush or small trees? (It will be going into a 6'-8' wide bed along my back fence, surrounded by perennials.) Thanks for your help!

Adrian Higgins: Fothergilla in sun only if the soil is well amended with rich acidic loam. You might try a related witch hazel, which seems better suited to taking brighter light.

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Washington, D.C.: Two questions:

1. I have a boxwood shrub that is in distress. It seems the leaves on 3/4 of the shrub have has died. Do I cut away the dead parts and wait for new to grow in, or will new leaves grow back?

2. A large black walnut tree in my neighbor's yard has stretched its branches across my lot and into another neighbor's yard as well. It is endangering our power and phone lines. Whose responsibility is it to trim the tree? Can I have it done without the permission of the neighbor in whose yard the tree originates?

Thank you!

Adrian Higgins: You need to find out why the boxwood is dying. It probably needs moving or re setting in a better draining environment. Once you have done that, cut it back to stubs, and it will regenerate, if is survives the transplant.
I believe that a property owner has the right to remove limbs overhanging his/her property. I would get an aborist to look at the tree and see what needs doing, and perhaps check with your city arborist.

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Washington County, Md.: The previous homeowner installed several large planting beds and put down heavy landscaping fabric in them. There is a lot of open space in these beds that is only covered in the fabric and mulch. I would like to put in more plants (more plants, less mulch!). But to plant would seem to mean removing the landscape fabric which seems a shame. Would it ever work to plant annuals in a layer of soil OVER the landscaping fabric? Should I consider planters or raised beds, or take out the fabric?

Adrian Higgins: You should cut a cross in the landscape fabric and plant through it.

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Manassas, Va.: I created a large garden bed this spring, but did not use mulch, nor did I keep up with the weeding. The result now is a large, weedy, unsightly mess. I want to avoid recurrence of this situation next year, so I came up with the following plan: Mow down the weeds now.
Reduce the bed to a more manageable size. Cover with mulch now.
Plant individual plants in the spring, rather than seeds, so that I can distinguish between desired plants and weeds.

Any other suggestions or amendments to this plan? Thanks!

Adrian Higgins: If you mean a vegetable garden, you will have to continue to weed to prevent your veggies, whether sown or planted as seedlings, form becoming overtaken by the weeds. The easiest way to distinguish between good plants and weeds is to sow your veggies in a straight line. Mark the line with a wooden stake. Anything outside that furrow can be weeded, and should be.

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Alexandria, Va.: Dear Mr. Higgins: Our dear friends from Holland sent us dozens and dozens of tulip bulbs. Being Dutch, they assumed we would know what to do them. My experience in gardening is growing herbs in pots on our deck. We have a normal sized suburban (ie. very hard soil) lawn with woods in the back. We would appreciate any hints on how, when, and where to plant. Ta.

Adrian Higgins: It all goes back to the quality of one's soil. The poorer the soil, the more laborious it is to plant bulbs. There are ways of speeding bulb planting. One is to till an entire area and shovel out trenches and plant accordingly. Another is to get a bulb planter with a long handle that one works with one's legs. The legs are much more powerful muscles than the arms. This is speeded if you have a partner, who is kneeling and depositing the bulbs as you go.

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Arlington, Va.: Dear Adrian,

Per your advice, I aerated my lawn, covered it with Compro, and raked good seed into the composted material. My question is whether I should use any fertilizer (low nitrogen?) this fall, and a preemergent in the spring.

Thanks.

Adrian Higgins: If this is a lawn overseeding, then yes, fertilize later this month with a high quality, slow release nitrogen fall lawn fertilizer spread at the correct setting. This will avoid burning the new seedlings. Yes, I would probably apply a preeemergent crab grass killer next March. Hopefully, by overseeding you won't need to do much by way of weedkilling, however.

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Washington, D.C.: I started a new lawn by using seed a number of weeks ago and the grass has grown unevely. I applied a second round of seed to the areas that are bare. Now the first round is long enough that I need to mow the lawn but i am afraid od damaging the "upcoming" or "incoming" grass.

Please advise!

Adrian Higgins: You can and should mow the earlier sowing, just make sure that your mower is at its highest setting and that you use either a new blade or a sharpened old one.

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Florence, Ala.: I love your chats and read them as often as possible.

I have found much advice online concerning the care of Poinsettias, but nothing about re-potting them. My mom has a Poinsettia that she transplanted to her garden after the holiday season (after being told by her cousin in San Antonio how well it worked at her house). She has now realized that, unlike her cousin, she must now prepare to bring it inside for the winter. The problem is that the plant has grown too large for most indoor pots. Can we divide it, or must we find a pot in which to fit the entire plant?

Adrian Higgins: The problem is the poinsettia in nature is a very large shrub and is rendered bushy by commercial greenhouses by using growth regulators and pinching regimes. I would cut it back hard, knowing that this may harm the "flowering" and then continue to cut back tips through the growing season (outdoors in summer) until you have created a bushier specimen.

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Annandale, Va.: Dear Adrian,

I hired a large company to add some organic matter (LeafGro) and mulch for the trees in my yard. As it turns out, they buried the tree trunks with up to 8 inches, right on the trees' bark. I was stung by yellow jackets just after the work was done, and was unaware of the extent of the damage that was being done. Finally, 18 days later, as I started to clear around the trees, I realized the damage done as some bark fell from the trees' base and insects were visible.

Do you have any thoughts about this? All I know is that an unsolcited tree removal guy came by and left his card a week after the job.

Signed, Every muscle in my body is still sore and I paid $4,000 for the privilege.

Adrian Higgins: I doubt that 18 days is enough to "cook" the tree bark, but you did well to remove the mulch from it. No arborist worth his or her salt would permit bark to be mounded against a tree, and a company that does that is demonstrating its incompetence. The mulch is composting and burns the bark off the tree. This also promotes mice and other tree pests. Moreover, it causes the surface roots to move into the mulch pile. When the mulch disappears the roots are left to dry with disastrous results. Mulch can be arrayed as a saucer around a tree bole, but only to catch rainwater and direct it inward. The mulch itself should not touch the bark.

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Alexandria, Va.: Hello,

An upper quarter of my grassy backyard hill has converted itself from grass to moss. The squirrels pull up sections like old carpet. Can you recommend a technique or a particluar grass to use to help fix the problem? (The moss has always grown by the wooden fence in the shade, but it seems to be expanding into sunnier areas.)

Thanks!

Adrian Higgins: I would cultivate a moss garden there, and make sure that the tufts that are dislodged and quickly set back against the soil, much like a divot on a golf course. Keep it misted.

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Alexandria, Va.: Hi Adrian -- Really love all the info I get from your chats. Need help with this. Assuming our area has three seasons of vegetable garden growing, what vegetables would you plant for each of the the three seasons in a plot 20' X 30" to maximize to the fullest the yearly harvest. Thanks.

Adrian Higgins: The list is too long to repeat, but if you call up the website of the Maryland Home & Garden Information Center, you will see I think under online publications something called Planting Dates of Vegetable Crops in Maryland, which will give you a sense of what can be grown when.
I am planning to grow greens through the winter this year under poly tunnels.

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Washington, D.C.: I had some calla lillies in a pot this year, which did nicely. The flowers are long gong, but the foliage is still green and healthy. Should I wait to pull up the bulbs (tubers?), or are the bulbs still getting ready for next season? Thanks!

Adrian Higgins: As with caladiums, callas are not reliably hardy here and should be lifted and stored.

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Columbia, Md.: Is there a magic to growing peonies? I planted six nursery stock plants in the ground this spring. On two of them, the leaves turned brown, then black, and they died. Two others seem to be okay. I have added soil conditioner and lime to the flower bed where they are. The last two in containers seem healthiest of all. Should I overwinter those two in the containers to be on the safe side?

Adrian Higgins: The fact that the ones in the containers survived is telling me that you planted the others in soil that was too wet and poorly drained. Peonies like rich soil but need drainage. I would plant the potted ones now in a sunny, well drained site, setting the crown of the plants one to two inches below the soil level. Mulch lightly and water them occasionally until they are established. It will take a year or two for them to begin blooming, so be patient.

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Arlington, Va.: A beginner question: What is the best time of year (fall?) to trim roses and evergreen bushes?

Adrian Higgins: Bush roses are best pruned in late winter. If you prune them now, you may encourage new growth that will be tender and killed by freezes. Also, the whole plant will be more vulnerable to winter kill. So, prune them back hard in February, down to about 18 to 24 inches, leaving just five or six healthy canes.
Evergreens are best pruned between also in late winter, while they are in dormancy and before their spring flush of growth. However, virtually any time is a good time. You will remove the flowers of anything that blooms up until June but that may not matter on something as floriferous as an azalea.

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Washington, D.C.: I have a tree box that I would like to put some plants into. Can you give me a few ideas about what would be the best choices for a bright light spot that will be gassed regularly by cars and buses? I have a couple of hostas in there and the variagated version of the grass (?) that sends out the pretty spikes of purple flowers in September, but any other ideas? Tough ferns? Thank you!

Adrian Higgins: Your light yellow grass is variegated liriope, which comes in different sizes and colors, depending on variety. They make great, bulletproof tree box plantings. Ferns are not for tree boxes, in my view. The soil is too poor and dry.

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St. Mary's County, Md.: Mr. Higgins: a tree question for you. I want to plant a tree where we recently removed an old tree (the removed tree died due to damage to it's roots during a construction project). However, I've read that you should wait three years before you plant a tree in the same location. Is this accurate? And if so, why?

Adrian Higgins: The three years is quoted, I suspect, as the period it takes for the old roots to die and rot away. Some trees put out toxins that discourage others from growing, the most obvious example is the black walnut. I have not been shy about planting around old tree stumps and have had no discernible problems with getting new trees to grow. Just make sure that the old stump doesn't resprout, and if it does, be diligent in removing the suckers.

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Alexandria, Va.: Is it possible to propagate ferns? If so, how?
Thanks!

Adrian Higgins: I am not a fern expert, but ferns that spread by rhizome can be separate as divisions, otherwise you can raise them from their spores. If you are interested I would consider joining the American Fern Society. In addition, John Mickel of the New York Botanical Garden has an excellent book, still in print I believe, called Ferns for American Gardens.

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Annandale, Va.: I have some winter blooming camelias that have already started blooming! Typically they don't flower until December. Do you think it's due to the wet summer?

Adrian Higgins: The moisture may have made them a bit precocious. Possible this is their first year in their current spot and have found a microclimate that makes them flower early.

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Fairfax, Va.: With all the rain this summer, my zinnias grew to absolutely monster proportions! The flowers were beautiful, but now the leaves are covered with mildew and it's time to pull the plants out. Can I put the mildewed plants in my compost pile? I hate to waste all this great bounty of plant matter.

Adrian Higgins: I think you can because mildew spores are everywhere, and the risk of having them in your compost is not going to make much of a difference in their return next year. If you want to diminish mildew problems, select varieties bred to be resistant and place them in a sunny, breezy location.

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Washington, D.C.: We moved into a house about a year ago that came with a lovely Asian-looking pine tree. It almost looks like a tall bonsai -- thin trunk, greenery at the top and on random thin branches along the trunk.

In the last month or so, several green parts have quickly turned brown. I trimmed them this weekend, but it's still spreading to other green areas. Do you have any advice considering I have no idea what this tree is?

Adrian Higgins: I have just talked to Susan Martin, conifer specialist at the National Arboretum for a second opinion. If the needles are falling from the tips of the branches, that's bad news and is probably related to the pine being in too wet a location. If the needle drop is from the interior, it is probably just the natural cycle of dropping of old needles. Old pines don't move easily, you may be able to improve the drainage into the pine bed.

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McLean, Va.: I have read that hardwood mulch takes nutrients from the soil as it decomposes; is this a problem with pine bark mulch?

Adrian Higgins: I think so because much of what is sold as bark mulch is not, it is shredded wood, not shredded bark. And as green wood it absorbs nitrogen as it decomposes. The remedy is to apply some fertilizer at the time of laying the mulch, though I actually wouldn't do that at this time of year because you will encourage tender new growth.

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Wilton, Conn.: I have two magnolia trees planted too close to the house as foundation planting. They have been cut back severely and are regaining their leaves. Now I want to transplant them to the open yard where they will have more room to grow. Any suggestions on how to move them successfully?

Adrian Higgins: Magnolias are best moved in the spring. I would root prune them now by taking a sharp shovel. Imagine a circle around the tree, perhaps 30 to 36 inches across, and slice a dotted line along the circumference. This will encourage the regeneration of roots without total root trauma, if you catch my drift. Move them after they bloom next April.

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Richmond, Va.: Adrian:

Thanks for these fora. We have mostly blank bed beside our house which is about 15 feet long and 2 1/2- 3 ft wide. Boxwoods take up about the first four feet toward the front of the house. Looking for some interesting plants to fill in. Space gets a little sun in the midafternoon, is mulched and fairly well drained. Any suggestion, especially for some color?

Many thanks.

Adrian Higgins: I would forget about the flower color and plant something of textural interest, maybe some sweet box, Japanese painted ferns, and liriope.

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Washington, D.C.: I have some ugly Yew Bushes in front of my house -- a little townhouse with a small front yard, and sidewalk.

Any suggestions for something else that could be a border by the sidewalk. A nice shrub mayb e with some color in the fall, texture, not boxy yews?

Also, what time of the year is best to make the change?

Adrian Higgins: Actually, some of the varieties of nandinas are wonderful, including dwarf varieties. Our hour is up, thanks so much and see you next week. Get those bulbs in, and do some watering, it has been dry now that Jeanne is a memory.

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