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.

He was online Tuesday, May 13 to offer advice on lawns, flower beds, vegetable patches and window boxes.

A transcript follows.

Catch up on previous transcripts of The Garden Plot.

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."

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Woodbridge, Va.: Good Morning, I'm submitting early, so I don't forget. We have a 20 foot sycamore in our front yard. It's been in the ground for nearly 2 years and we took the stakes off last year. It has been doing great. But the heavy heavy winds and the water-soaked ground have pushed it to 'the east' so it is now about 20 degrees off center. What can we do? Do we push it back to center and re-stake it? Your advice is greatly appreciated! Thank you!

Adrian Higgins: It's still young enough to get it upright, which is important because the lean will only get worse as the tree grows and as you know, a sycamore will become huge. I would knock in a metal stake about three feet from the trunk and use a guy wire to coax it vertical. Put a section of hosepipe around the wire where it touches the bark, to lessen any girdling. Check it occasionally to make sure the hose is still in place. This shouldn't be on the tree for more than a year or 18 months.

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Pistachio shells: Someone asked about pistachio shells in pots for drainage last week; you thought they might get mushy. Trust me, they won't. I put pistachio shells in my compost and they aerate the soil beautifully...and two years after spreading the compost I can still see the shells.

Adrian Higgins: Useful to know. Let's go nuts.

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Richmond, Va: I read that vinegar is a good organic way to kill the wild strawberry weeds in my yard. Will it also kill the grass? Amy trying to solve by pulling the weeds, but they keep coming. Thanks.

Adrian Higgins: Household vinegar is not strong enough to act as an effective herbicide. If you find herbicidal strength, yes then it will kill the grass as well. After this rain, I think the little crowns of the plants will lift pretty easily.

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Silver Spring, Maryland: What's eating my spinach? I am growing romaine, black seed lettuce and spinach in a semi raised bed. All are growing nicely, but something is eating the spinach. It starts with small holes in the leaves, in some plants, the leaves are eaten clear down to the stems. How can I stop this?

Adrian Higgins: Probably slug damage. Will we see an epidemic of slugs following this rain. You can use beer traps or pick them off at night.

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Wheaton, Md.: Can you please provide a link to your article on snake plants? I have one, close to 30 years old, that needs to be replanted.

Thanks!

washingtonpost.com: Charmed Even By Snake Plants (Washington Post, Jan. 31)

Adrian Higgins: All done by the magic of my producer, Elizabeth. Thanks.

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A rose by any other name?: Adrian, I need your help. My largest rose bush is getting yellow leaves that then droop and get brown spots and then fall off. I've tried spraying it all over with the organic three-in-one bug/fungus/aphid stuff that Home Depot recommended but other then that I've no clue. It is not working. At this point I'm fine with either organic or toxic methods as long as I save my huge lovely rosebush.

Adrian Higgins: These three in one sprays are not good gardening practice, you should only spray against something if it is clearly a problem, and having black spot doesn't mean you have aphids, for example. Here's the secret of growing roses without blackspot, give them good, rich soil and plant them in an area that gets good air circulation, prune them to improve air circulation, pick a resistant variety, and spray preventatively once or twice in April and May.

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Arlington, Va.: Hi Adrian, I love the chats. My husband and I are preparing soil for several beds around our house. The soil on our property is clay that has been very compacted from renovations done to our house. For the first of several beds we've finished digging up a bunch of clay and mixing in some organic material. Now we have quite a bit of excess lumpy clay soil sitting in our driveway. There's nowhere to put it on our small property and the problem's only going to get worse as we enhance soil for the rest of the beds around the house. Do you have any suggestions for getting rid of this excess clay? Thanks!

Adrian Higgins: I don't know if your local government allows you to put soil in the trash. If not, I would consider adding the clay, a little at a time, to a compost pile.

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Waterlogged garden...: I planted my garden Sunday morning and the back part of it was underwater for a good part of yesterday (though no standing water now). Anything I can do to ameliorate the damage?

Thanks!

Adrian Higgins: The first thing would be to stay off it, to avoid soil compaction. This was a lot of rain, so some waterlogging might be expected. If it is still saturated by this weekend, I think you would have to build up the beds more. Both seeds and young plants will rot after a few days in waterlogged conditions.

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Chevy Chase, Md.: Hi Adrian -- Avid gardener with a chronic problem. Why do some of my oak leaf hydrangeas flop over, while others are huge, happy and straight? I've tried to use peony supports for the floppiest of the bushes, but they are no match for the weight. How can I improve their posture?

Adrian Higgins: If they are in shade, they will have tendency to flop. You can also prune the largest branches back.

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Manassas, Va.: Really just a comment:

I have tried all means of staking tomato plants through the years. In Virginia there are so many rocks in my garden I can never can get posts pounded in very easily and I have been using round wire cages for the last few years. At least one of the four legs on the cages ends up hitting a rock and cannot be bent enough to go into the soil very far and they usually require staking with a post later in the season especially with the grape and cherry varieties or they will end up falling over anyway. I was stacking the cages this season to move them to the garden and I realized that they would be much more stable if I used them "upside down." So I tied the legs together to form a dome and used 2 small stakes (18")for each cage to hold the base onto the soil. The small stakes can be moved anywhere around the base of the cages which eliminates the difficulty of hitting rocks below the surface and I tied them to the cages just above the second ring to hold them down snugly. I planted very early and I think it is going to work just fine. Have you ever heard of this?

Adrian Higgins: No, but when you are feeling energetic this fall, I would get a sturdy garden fork and double dig the bed for next year, and pry out those rocks as you find them.

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Crape Myrtle flower color: Thank you for taking this question. I was wondering if I can control the color of crape myrtle flowers by adjusting soil acidity level -- same way one can control hydrangea color?

Adrian Higgins: I don't think so, Hydrangeas react to the amount of aluminum in the soil, why other flowers don't is a mystery to me, except perhaps the "petals" of hydrangeas are actually calyxes.

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Re-visit: Have we killed our Crape Myrtle?: : Well, it's been two weeks, not a sign of a leaf... and still green cambium layers. We can't reach the outer reaches of the branches to trim the dead twigs off, so I guess it's a goner.

Bummer!

29 April, I wrote: Oh dear, and heavens! Our very mature (and in need of pruning) crape myrtle has not a sign of leaf or bud. 20 feet tall, and last fall we took out some nearby ancient privet, leaving the small nandina and hydrangea under the CM. The cambium layer is green on the main trunks, but the farthest twiglets are quite dry.

Should we prune, pray to the crape myrtle gods, or plan on a new myrtle?

Thank you muchly!

Adrian Higgins: Be patient. In a week you will see leaf growth. Check in next week and tell me if I was right.

Adrian Higgins: I was wrong. My crape myrtle has foliated. But if the cambium is green, there might be some hope. Even if you remove the branches, it may grow back from its crown.

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Chapel Hill, N.C.: I have two beloved smallish variegated daphne odoras that came from clippings two springs ago, now both in containers in a shady location. They did fine until two weeks ago, when the lower leaves of both plants turned quite yellow. They had already been fertilized, so I added some liquid iron. One has gotten much worse, and the other is starting to yellow again. Do you have any suggestions? No obvious bugs or other problems. Many thanks!

Adrian Higgins: I wonder if they are either in an area of poor drainage, or are going into the normal Daphne abrupt death spiral. They usually wait about 10 years before doing this. If they die, lift them to see if the soil is draining properly.

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Posting early -- Vines?: Thanks for answering last week about my schizophragma. I have the same question about cardinal climber and hyacinth bean vine; what do they need to climb on? Netting, string, a trellis? Or should I put them in a railing-box on my deck and let them dangle down? The deck gets direct sun only at midday.

Adrian Higgins: Both twine on any support you can give them.

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Brooklyn, N.Y.: I have arugula and red leaf lettuce growing together in the same pot. It's a wide pot, but it's clear it's not big enough for the both of them. So which do I transplant? Is one more fragile and sensitive to repotting than the other? Or are they both bad to transplant and would I be better off just leaving them as is? I'm afraid to make a move before hearing your expert advice. Thank you.

Adrian Higgins: Both will eventually bolt in the heat of June or July, so enjoy them now, and use them.

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Davidsonville, Md.: Good morning, Adrian!

My house will be undergoing some major renovations in the next few months (well, really it's being torn down) and I'm wondering what landscaping shrubs would be worth saving. They'd need to be dug up and transplanted temporarily.

There are quite a few very large American boxwoods (five or six feet), maybe a couple of English boxwoods, some shrub hollies about four feet in diameter, and a not-so-old Natchez crepe myrtle that's about 15 feet tall with 2 inch diameter trunks.

Azaleas and rhododendrons should probably be abandoned, right?

Are garden centers ever interested in buying or trading large plants?

Thank you!

Adrian Higgins: Nurseries are rarely interested in taking old stock, they want young, compact and primed plants in top shape. I once wrote about a nursery that recycled old shrubs and trees for wealthy clients, but those places are rare and, I suspect, getting rarer given the state of the housing market. Your azaleas and rhodos should move relatively easily, as will the boxwood. The crape myrtle probably won't lift so well. You can ball and burlap them and heel them into a nursery bed.

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Washington, D.C.: Adrian, I read with interest your opinion about wild cherry trees (NOT the beautiful flowering trees on the Mall...). I have a large one in my yard, and while I appreciate that it gives my south/west facing house its only shade, it drops thousands of tiny cherries each summer, resulting in thousands of seedlings coming up in my yard each spring. I pull them up but it's quite a job. Plus I get the tent caterpillars you mentioned, sigh. I was wondering about applying something that would prevent the cherry seeds from germinating -- is there anything that will accomplish this without nasty chemicals? Would also appreciate advice on relatively fast growing shade trees in case I decide to replace this tree one day... perhaps plant a replacement tree and after a few years cut down the cherry.

Adrian Higgins: It's not my favorite tree, and even if there were a chemical treatment for sterility (as there is for ginkgo) I wouldn't bother, too much trouble and expense. I would remove it and replace it with something like, upright Japanese maple, stewartia, even a crape myrtle.

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College Park: I am entering year 2 of an infestation of voles. They have decimated my liriope, hosta and other fibrous rooted perennials as well as hyacinth bulbs. They even gnawed the roots off of a nandina this year! Last year they helped themselves to bush beans in the vegetable garden, stuffing their holes with the beans. I have been using Mole and Vole repellant that includes 10% castor oil regularly throughout the past 12+ months with little success. Any other suggestions besides cats?

Adrian Higgins: Cats are the most effective. My colleague Barbara Damrosch wrote a column about vole control using a trap invented by her husband, Eliot Coleman. Here we go:

A Game of Whack-a-Vole

By Barbara Damrosch

Special to The Washington Post

The tiny, furry body hurtles across the gravel walkway, from the shelter of one garden bed to that of another. It is a meadow vole (Microtus pennsylvanicus), a mouselike rodent that nests and hides among grasses and other herbaceous plants, munching heartily as it goes. When in full view, it is always on the run, to escape the eyes of its many predators: hawks, crows, ravens, owls, foxes, raccoons, possums, skunks, weasels, snakes, snapping turtles, bullfrogs and certain fish -- not to mention cats and dogs. The life span of a vole is brief -- a year or so at best, and 80 percent die before maturity. But as I watch the one in question disappear into the leaves, neither these grim statistics nor the creature's cuteness inspires much pathos. It is headed straight for my beets.

As generally happens in nature, this vole's vulnerability is balanced by strategies that have insured the survival of its species. It has had a long time -- since the Pleistocene era in fact -- to develop not only speed and cunning, but also a reproductive strategy that puts most mammals to shame. A female vole can get pregnant when less than a month old, deliver three weeks later and get pregnant again that same day. Breeding in all seasons, she might have as many as 10 litters in a year, with five or six babies in each. Though meadow voles prefer grassy areas, especially moist ones, they are highly adaptable and are common in most of the United States.

Voles are easily confused with mice (which are smaller, with longer tails), shrews (also smaller, with more pointed noses) and moles (which have outward-facing, digger's hands). Meadow voles, sometimes called field mice, are five to seven inches long, counting the tail, and plump, with dark beady eyes and brownish fur.

If you are a gardener, you have probably seen places where they have been. Perhaps some spring bulbs you planted never came up, Maybe you went out to divide a clump of hostas or Siberian iris and found that someone had already done this for you and half the roots had vanished. Or you noticed that the lower bark of your precious young fruit trees had been girdled by tiny teeth, and the trees are now dead. Or that the fall lettuce you had hoped might overwinter has been devoured in patches, and some of your winter carrots and parsnips to boot. If a network of narrow surface runways has appeared -- as if miniature dirt bikers had held a rally in your garden -- then voles have been in residence. If you find a ball of woven grass hidden beneath what's left of your plants, in a slight hollow in the soil, that's where a mother has reared her young. No sentiment, please. No matter how reverent we gardeners may feel about the web of life, there are times when the list of predators must include you.

The first line of defense against voles is to keep the areas right around garden beds closely mowed, thus exposing the intruders to predators. Cutting back herbaceous perennials in fall, removing weeds and debris, and using only shallow mulches are all good techniques, though they can pose a dilemma. I like having a natural landscape with fallen leaves, some underbrush, some tall grasses and forbs left standing as cover for winter birds. So I just mow around vulnerable food crops and plant them with ample space between the rows. I wrap young trees in mesh cylinders made of metal window screening, buried an inch or two at the base and stapled at the sides, leaving plenty of room for the trunk to grow. A circle of crushed stone around the base of the tree is a good idea, too, especially if pine voles are at work (these are more apt to burrow in the soil, and destroy roots). The same collars will protect against borers and, if about two feet tall, against rabbits as well.

When vole populations soar, as they often do, I have to resort to trapping in order to save plants that I value. Plain old mousetraps work -- up to a point -- if you place them perpendicular to a well-used runway, with the trigger right in the path of their oncoming feet, and baited with peanut butter, apple or bubble gum. But the voles in our garden have learned to associate these flavors with death, so we've found a better method. Unbaited traps are set in a simple wooden box equipped with little entrance holes in opposite sides of the box walls. The traps are just inside the entrances. If the box is placed in a runway, voles will scurry into the box to hide, and land on a trap. The top lifts off for prompt removal.

I have no plan to wipe out all the voles in our little piece of earth. They're a vital food source for the owls I love hearing at night as I'm falling asleep, for red foxes that venture out from the edge of the woods and for the hawks that perch in our trees, scanning the ground. To work, the system needs both predator and prey. But, guys, those beets are mine.

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Upside-Down Tomato Cages: This does work, we had a similar situation years ago and it was a good solution. The only caveat is to make sure that the "tops" are secured together well so that you don't get poked in the eye or elsewhere later when the leaves have grown through and covered the cage.

Adrian Higgins: Yes, I was thinking that you don't want those spikes sticking up at eye level. You should take some pliers and bend them down.

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Washington, D.C.: I have several perennial salvias in my yard that are beautiful and easy (the variety is Caradonna). This spring one of them sent out a few shoots that have variegated leaves and lighter purple flowers. I'm sorta wondering if I've discovered the next greatest thing in perennial gardening (can I root cuttings?) or if maybe my salvia just has a disease... please advise.

Adrian Higgins: This is where all variegated plants come from, sports that are then propagated by cuttings. It won't make you rich, but it might be fun to take a cutting and grow it on.

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Shepherd Park, D.C.: A question and a suggestion about tomatoes.

First the question: Can you recommend a reliable high-acid slicing tomato that won't be too susceptible to wilt and blight? I garden in a community garden plot, so there are spores, etc. all around, and nonresistant heirlooms usually succumb.

The suggestion for the person asking about staking tomatoes: Try buying road mesh at Home Depot or another home store and make your own. I bought some and rolled it into cylinders -- they are about 5' tall and are sturdy enough to support even the most vigorous plants. I stake them with one regular wooden tomato stake woven through the cage and they never fall.

Adrian Higgins: I think Better Boy is an excellent disease resistant slicing tomato. Thanks for the suggestion. I think that mesh is used to reinforce poured concrete.

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Washington, D.C.: Adrian,

I am interested in planting a peach tree in my new back yard. Judging from the number of peach pits back there, there was such a tree at one time. Do you have any advice on particular types of trees, both from a growing in this area standpoint as well as taste? I have only looked at Home Depot so far, and they had two or three types, but I didn't really know anything about them.

Thanks.

Adrian Higgins: I would check out a specialty fruit nursery such as Edible Landscaping. You want varieties that are going to be as resistant as possible to brown rot, and you may still have to spray against it.

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Herndon, Va.: Hi,

I have planted some dahlia bulbs in the first week of May and now with all the heavy rains, I am wondering if the bulbs would rot? What are the chances of survival and do you suggest that I pull them out and see how the bulbs are?

Thanks

Adrian Higgins: If they have initiated growth, I think you will be all right. But again, if the soil has not dried by the weekend, you should lift them, improve the bed and reset them. Be careful not to break any bud or emerging stalk from the crown.

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RE Clay Disposal: I always dig up tons of clay and put it in the brown garden bags along with other garden waste. I don't know if I'm supposed to be doing that, but they always take the bags, which are crazy heavy, so they must know what's in there.

Adrian Higgins: Secret: I have been known to do the same.

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Mt. Airy, Md.: Hi and thanks for taking my question. My backyard backs up to a nature preserve. Is there an easy solution in transitioning from my lawn to the weeds in the nature preserve, such as a natural border of some type?

Adrian Higgins: Absolutely, you could plant a margin of native grasses or sedge.

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D.C.: What do you do with overgrown plants and plants you don't want anymore?

Adrian Higgins: Many overgrown woody plants can be trimmed back, even hard. Plants that are surplus could be given to neighbors or to community gardens.

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Donating boxwoods: Maybe not a lot of nurseries take old stock, but when we wanted to get rid of huge old boxwoods growing around our front door and windows (about ten cubic feet per side), I found a couple of regional associations of landscape designers on the web (sorry I don't have the info to post, this was two years ago) and had lots of landscapers interested in taking them ("free to a good home"). They were dug up and moved to a historic site on the Eastern Shore.

Adrian Higgins: Yes, that's an option. Especially English boxwood, and weeping Japanese maples. Though I might ask some money for them.

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Germantown, Md.: Hi, there is an area of my lawn that gets soggy occasionally, well after this weekend everything is soggy. Are there any shrubs that like their feet wet? That the dogs can't run over?

Thanks so much!

Adrian Higgins: Deciduous hollies (Winterberry, Sparkleberry), Myrica, Willow, red-twigged dogwood, Aronia.

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Re: Snake plants: How can I support a somewhat floppy plant - or better yet, why is it floppy? I have it in a fairly dark area - how much light do they need? This one, or pieces of it, date to the 1970s at the old Garfinkel's on 14th Street!

Adrian Higgins: Shade will encourage them to flop. Don't overwater and put in a bamboo stake and tie them.

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Chevy Chase: Hi there - I am digging out the entire front of my house to waterproof it (yes, this last storm put me over the edge!) but will need to remove a pyracantha that is trained against my chimney to do so (as well as lots of daffodil bulbs and some Japanese irises). Any suggestions on how to move all this stuff and keep it until the work on the house is finished? Thanks so much.

Adrian Higgins: I think the pyracantha won't move, the others will easily. Watch out for the thorns on the pyracantha.

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Alexandria, Va.: Our backyard is heavily clay and we have 5 oak trees. We've been wanting to plant a dogwood to give some color and variety. Would now (with the water table so high) be a good time to plant or would we just rot the roots? Can we plant later in the year? Next month? Any other advice (i.e., Chinese or American) on planting a dogwood in partly shaded yard?

Adrian Higgins: Sounds like a perfect spot for a native flowering dogwood. I dislike the rose colored variety, which I find a muddy pink. Go with an improved white variety of Cornus florida. If you want something a little different, you could try Cornus contraversa.

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Outer Banks, N.C.: Can naturally dried beach seaweed be used as a mulch around perennials/shrubs? I see seaweed extracts sold as fertilizers (very expensive). If seaweed can be used, do we need to wash first to remove salt residue?

Adrian Higgins: Yes, wash off the salts first, and it makes a great soil building mulch.

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Falls Church: I'm looking for a dwarf weeping Japanese red maple and can't decide between the inaba shidare, the red dragon, or the Crimson Queen. I'm leaning towards the red dragon because it's the smallest. Suggestions?

Adrian Higgins: I would go with the one with the most pleasing leaf shape and fall color.

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Springfield, Va.: Hey Adrian,

My yard is infested with wild violet. Personally it doesn't really bother me and I certainly don't want to spend hours upon hours trying to dig it all up. Is there anything wrong with not worrying about it, aside from cosmetic reasons?

Adrian Higgins: It will spread everywhere. This is the moment to extract it, now that the soil is moist. A fish tail weeder is an effective tool.

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McLean, Va.: Well, I had a large silver maple cut down a few weeks ago and the buds (aka helicopters) went everywhere. Now, they're starting to sprout in the mulch beds. Hundreds of them. What to do?

Adrian Higgins: A sharp weeding (not hilling) hoe should do the trick.

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Alexandria, Va.: Tree pruning question for you -- how much can one prune back branches on a cherry tree before doing irreparable harm to the tree? We have 6 yr old cherry tree in our front yard (don't know the variety -- looks like the ones around the tidal basin) which has several long droopy branches hanging over our driveway. I pruned a few smaller branches a few weeks back and covered the cuts w/some sealant made for this purpose. OK for me to take off a few more branches? Thanks.

Adrian Higgins: You don't want to disfigure the tree, it's important to retain a pleasing shape. Minor branches can be removed OK. Any resulting water sprouts should be removed as they appear.

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Arlington, Va.: I have a number of volunteer foxgloves dotted around the yard that it would be nice to have elsewhere. Too late to move? And, on the excess clay, which is not supposed to go in the trash in Arlington, why not use it and some mulch to create mounded beds?

Adrian Higgins: I wouldn't move them at this stage. They are about to bloom. Heavy clay would form a crust as a mulch, and prevent plants from getting moisture.

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Arlington, Va.: I have 7-10 huge azalea bushes along my property line. They are about 10 feet high and equally as wide. I like them, my neighbor isn't crazy about them. Their "landscape guy" suggested that we cut them down to about one foot. Is this too extreme? I am afraid that we will just have a row of gnarled stumps that will then die and have to be dug out. A significant consideration is that they are on a slope and they are holding it in place.

Thanks.

Adrian Higgins: This would be an awful disfigurement. You can trim them back, quite hard, perhaps by half, but not to 12 inches.

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Fairfax, Va.: I need to rotate my tomatoes into different plot this year and I'm wondering if I should avoid planting certain other vegetables in the same plot as well. I would like to plant some beans, cucumbers, peppers, eggplant, or garlic. When rotating crops, is there a "rule of thumb" about what to rotate into a plot, or would simply putting something other than what was there previously be enough to give the soil a break?

Thanks.

Adrian Higgins: You want to avoid re-planting with plants of the same family, e.g. cabbages and broccoli, onions and leeks, tomatoes and potatoes and eggplants.

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Fairfax, Va.: Good sunny morning! In my yard, I have a plant that has leaves similar to daffodils (which I originally thought was a daffodil since it is among them), but has about 8 small white, very fragrant, flowers. It is a very deep bulb that has found its way into my flower beds. Do you know what it is?

Adrian Higgins: It might be an ornithogalum, which is known to spread. Alas, we have run out of time, but check out Thursday's Home section. Thanks for all your questions.

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