Springtime Gardening
Adrian Higgins
Washington Post Garden Editor
Tuesday, May 6, 2008
11:00 AM
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 6 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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Asparagus: We have a well established asparagus bed. However, we like thin asparagus, and are now getting a majority of giant sequoias instead. Is this inevitable or do we need to grow another variety? If so, do you have recommendations?
Adrian Higgins: It's a product of the age of the plants. Just harvest them young and they should be tender and delicious.
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McLean, Va.: Hi Adrian. Love your chats.
I drank too much coffee one day recently. The result: small plots encircling six of my fence posts, in which I planted seedlings of canary nasturtium, cardinal climber and blue morning glories. They will get sun all day here, so I water them every day.
They are planted in potting soil and I have begun spraying an organic plant food on them. So far (2 weeks) they look great, but I realize we have the hottest part of the summer to go.
I'd appreciate any other advice. Not sure I fully thought this one through...
Thanks!
Adrian Higgins: The nasturtium will prefer some shade. The others are tender vines, I think the coolness is leaving the station and we will have warm weather soon and they will be fine. go easy on the feed, which the vines don't really need. Heavy feeding of nasturtium will reduce the flower display.
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Columbia, Md.: I'm a serious gardener on a 1/5 acre lot that has exhaustively asked neighbors to seal under decks/sheds once groundhogs move in... they can wipe out a garden quickly and multiply throughout the neighborhood. One neighbor allowed 5-6 to move under his deck and each season they move to another neighbor's yard. A fence is not an option but I've had some luck with a motion sensor sprinkler. Have you done battle with groundhogs?
Adrian Higgins: No, but I feel your pain. They are serious pests of the home gardener and can ruin a vegetable garden. I would ask your local animal control department about trapping.
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Chambersburg, Pa.: Sigh. We have a lot of garden and less energy these days. There are trees, shrubs, 9 perennial-and-bulb beds, hedges, and lawn. We want to enjoy it all but minimize the work. Do you have any suggestions for aging in place in your garden?
Adrian Higgins: You can slowly replace the perennial plantings with groupings of shrubs, but do be aware of mature sizes and space accordingly. A light mulch will reduce weeding and watering needs.
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Unbalanced Azaleas: My West-Southwest facing hedge of azaleas bloomed furiously last year, but this year very unevenly. They kept their leaves and did not show any obvious drought stress. Was I supposed to trim them back last year? Do you know the reason for the uneven blooming?
Adrian Higgins: I would say the drought may have hampered bud formation last summer, someone may have pruned them after July, and that someone may have been a deer.
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Washington D.C.: Some varmint (not sure if it flies or scurries) has eaten my oregano. And I fear other plants are being attacked. We have a deck and live 2 floors up - building a fence would be impractical and probably not too effective. Is there something I can spray on herbs and other plants that will deter pests but not hurt me or the plant?
Adrian Higgins: Examine the plant for caterpillars and pick them off. If your herbs are in fairly decent soil, and enough of it in containers, then they will put out enough new growth to negate the effect of the pest. I would spring for bigger pots, fresh potting soil, and new plants. You don't want to spray culinary herbs with pesticides, and you really shouldn't have to if they are grown well.
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Springfield, Va.: I understand dogwoods are highly likely to contract a powdery fungus and die. I'd love to plant one in my partial-sun backyard. Are the new disease-resistant "Appalachian" types developed in Tennessee generally available in our local nurseries, or should I order them online?
Adrian Higgins: I would check with local independent garden centers, they usually list their stock online these days. Dogwoods do suffer from powdery mildew, especially during late summer droughts, but that disease isn't the one to worry about so much as the anthracnose that can result in tree death. The disease is prevalent now, and during cool, wet springs (the sort we are having) You may want to spray against it. An effective control is to remove all the suckers or water sprouts that erupt from the bark, these offer a direct pathway into major limbs, and should be removed promptly.
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Washington, D.C.: Good morning. My question is about plant purchases in general. I purchased several plants (about 20, mostly herbs) from an organic farm that mailed them to me. No problems last year. This year, one died nearly immediately, a few died within a few weeks, and another is already on its last legs. I replanted them all in similar pots with organic potting soil, and they are in roughly the same place in my window (condo with no yard). My other plants with similar needs are thriving. (For example, my own basil from seed is growing like a weed but the basil that I purchased already grown is fading fast.) I realize that nature is unpredictable, but are there any standard guarantees when purchasing plants? Shouldn't they live for a while? What is the latest that I can contact the nursery (it's been almost 2 months now)?
Adrian Higgins: First of all, basil is a tender herb and should not be planted out in April. You don't mention what they others are, but I suspect your problems are a combination of jumping the gun and watering too much. Young plants have small root systems, which must be kept moist but not wet.
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Arlington, Va.: Love your column! I realize you get a lot of questions about screening options for small, narrow spaces to provide privacy from the prying eyes of one's neighbors. Our situation requires privacy screening that will grow to about 20-25' or so high, and that will spread to no more than about 4' wide. Since we are on a hill as well, our neighbors get a full panoramic view of our yard from their entire second floor. Fast-growing to 20-25 feet would be ideal. We were thinking of varying it a bit and not planting an entire row of the same thing, and for a number of reasons we want to go with evergreen. The length along the fence is about 25'. One person had suggested a few Nigra arborvitae, and maybe one accent cryptomeria (more than one would spread too wide for our space). We also really like the red tip photinia even keeping in mind potential fungus problems. Would you agree with the above, and could you recommend any other evergreen large shrubs/small trees that would be good fits for our narrow space? Thank you!
Adrian Higgins: The only plant I can think of that would grow to 25 feet high but only 4 feet wide is the Italian cypress, which won't grow here. This is a tall order. I would consider a ginkgo tree, which remains narrow. It is deciduous but the canopy would provide a veil in winter. Neither cryptomeria nor arborvitae will stay anywhere near four feet wide.
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Ashburn, Va.: I have a really nice flower garden going, to the dismay of my husband who would rather just see shrubs out front. But I love the color. I've been fairly successful at picking perennials that have come back bigger and better each year. But now - I need something to line the back of the flowers. I have quite a bit of space up against the wall of my house and would love something that will grow tall throughout the summer to offer a backdrop. Any suggestions? It is a high-sun area.
Adrian Higgins: Maybe some Rudbeckia maxima, or some Hibiscus moscheutos, or Joe Pye Weed.
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Soil quality: My homeowners association recently removed our small "tot lot" (playground), and plans to level the area and plant grass. The area had been bordered by big landscaping timbers, so when they removed that border this weekend, they left behind a raised area of what appears to be super-rich dark soil, created by 20 years of decomposing mulch.
My question is: do you think this soil is as rich as appears? I want to cart some away to put in my garden (and thereby save the association the trouble of carting it away).
Adrian Higgins: Yes, if it is well rotted, I think it would make a great amendment, but incorporate it with other stuff, including your native clay soil.
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Groundhogs!: We had our exterminators set groundhog traps, at which the groundhog laughed. We felt like Bill Murray in "Caddyshack" until one day, three months after the exterminator had given up checking the traps, when Miss Utility showed up and asked if she could have the groundhog in the trap, so she could take it to her farm, which was full of animals she'd rescued. Presumably she did not have a garden. I can only assume that it was the Feast of St. Francis of Assisi or something. Now on to actual gardening; was it you or your colleagues Lerner or Aker that published the recent list of "what animals damage what plants"? Voles, deer, etc.
Adrian Higgins: Thanks for this. I can't recall the exact article you have in mind. Scott and Joel have been talking about voles, deer and other pests for years.
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Purple Verbena: My office building has some ground cover that I figured out (with some google sleuthing) is purple verbena. I'd love to use it to fill in some spaces around my bushes and perennials. Does that seem like a good idea? And if so, does this type of plant usually come already grown or as seeds, and when should I plant it?
Thanks!
Adrian Higgins: A lot of verbena is grown as an annual. Verbena bonariensis is a tender annual but seeds like mad and will come back reliably. A friend recently put me on to Homestead Purple, which is said to be hardy in our ever warming city.
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Alexandria, Va.: I believe I have tent caterpillars defoliating my cherry laurels, although we have no "tents" in our yard. They don't look like the gypsy moth caterpillars that the county is now spraying to control. How can I protect my laurels (besides picking off and destroying the caterpillars, which I have been doing)?
Adrian Higgins: The tents are probably in Prunus serotina, which is the host plant and closely related to cherry-laurels. I think hand picking is the most effective and environmentally sound method of killing them. Drop them in a solution of bleach.
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Bethesda, Md.: My husband left me in charge of protecting our roses while he's out of town. Between the gypsy moth caterpillars, little green worms that hide out under the leaves, and flaky white bugs on the buds, I certainly have my work cut out for me. Do you have any advice for keeping these pests in line? Would spraying soapy water help? (We have an organic garden.) Thanks!
Adrian Higgins: I suspect you are seeing tent caterpillars and not gypsy moth larvae. Again, pick them off, but beware of the thorns. You could also try Bt on the inch worms, or insecticidal soap.
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D.C.: How do you remove tree stumps? I bought a container of Bonide Stump Out thinking it would work magic, but upon reading the instructions, it is recommended that the stump is left to season for 18 months before application. Then, kerosene and fire is used to burn the stump down.
Adrian Higgins: You can speed the rotting by keeping it wet, but the most effective method is to have it ground out by a machine. If it is a small tree (say less than three inch trunk width) I would take a sharp axe to the roots, and then pry it out. For future reference, it is also easier to leave five or six feet of trunk before doing this, so you have a lever.
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Arlington, Va.: Adrian, I was wondering if you had any updates on the status of the Arboretum and funding for it. Has there been any progress made? or is the future of the Arboretum looking as bleak as it was when you wrote your article?
Also, I know that the Arboretum has introduced a number of very popular/useful plants over the years. If the cuts go through, what will happen to this breeding/introduction program?
thank you!
washingtonpost.com: Plans Wilt at National Arboretum (Washington Post, April 26)
Adrian Higgins: Congress has until later this year to make a funding decision. I will keep you posted. If the proposed cuts go through, some of the collections will have to be neglected and I think they are figuring out which ones might do better than others in terms of picking which ones to abandon.
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Washington, D.C.: I have a chronically unhappy pink lemonade honeysuckle vine. Mold, aphids, you name it. It gets plenty of sun, air, water... Could it be that this particular cultivar just isn't made for D.C.? I will sound heartless when I say I'm tired of giving it so much attention.
Adrian Higgins: Honeysuckle is prone to massive aphid infestation in the spring, and the key is to spray it with water on a regular basis to keep the numbers down. It also gets mildew, but especially in a dry year like 2007. I saw a yellow flowering one the other day that was gorgeous, and worth cultivating, I would think.
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Alexandria, Va.: Thank you for all your advice! I do have a question on the species tulips. Do they also need to be dead-headed, a la daffodils? Should most perennial bulbs be dead-headed? Obviously not crocus, but ones like snowdrops and fritillaria? I appreciate your help.
Adrian Higgins: No I wouldn't dead head them, because the seeds are spread by ants and your colony will increase. This will not diminish the mother stock.
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Pacific Northwest: Thanks for taking my question Adrian.
The NY Times has a piece on replacing a lawn with moss. I live on the Western slopes of the Cascades and moss grows here like corn grows in Iowa. Not enjoying mowing my lawn much, the article caught my eye. What do you think of the idea? It seems to have some merit, at least to an amateur like myself.
washingtonpost.com: Moss Makes a Lush, No-Care Lawn (NY Times, May 1)
Adrian Higgins: I think you will have a lot more success in the cool, humid Pacific Northwest than in the (sometimes)dry and (always) humid Mid Atlantic. But moss gardens are not low maintenance. They must be kept moist and you must remove the leaf litter and other detritus that falls on them.
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Rockville, Md.: I have a potted lemon tree and avocado tree that have been indoors since I got them last November. Is it okay to bring them outside for the spring/summer, and then bring them in once it starts to get cool again? We have a full sun deck.
Adrian Higgins: Both would do fine outdoors now. I would place them in a site that gets a little afternoon shade.
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Schizophragma question: Posting early as I'm at work: A friend is giving me what looks like a schizophragma from her yard, and I plan to put it against a concrete wall. Does schizophragma have the same clinging mechanism that hydrangea petiolaris does? I don't want to have to put nails into the wall to support the vine. The Fine Gardening web site has an excellent description of the different kinds of "twiners and climbers" but it doesn't list schizophragma.
Adrian Higgins: Yes, it should attach itself OK. Sometime I will place a large stone on top of the wall, attach a string to it, and let the vine twine up the string if it needs a little extra help.
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Roses: I've had very good luck with neem oil spray, especially for black spot and Japanese beetles.
Adrian Higgins: Useful to know, I have had less luck with neem oil against blackspot.
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Falls Church: Let's say I planted a small tree or shrub in a larger container because my yard isn't ready for it yet, and a few years down the line, wanted to transplant it to the ground. What's the best way to remove this plant without breaking the pot?
Adrian Higgins: I wouldn't. Much better to buy a young tree or shrub when you're ready to put it in the ground. In a pot, it is likely to get rootbound, and may develop a girdling root. If the root finds its way out of the drainage hole and into the ground, you're in trouble. (I know, believe me).
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Bethesda, Md.: Thinking of putting two different blueberry cultivars in a raised bed that gets a good 5 hours of sun a day. Any advice on types and how I can expect to do?
Adrian Higgins: Sounds like a great plan. I would plant them no closer than eight feet apart and give them acidic, organically enriched soil and a light mulch of rotted compost.
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Silver Spring, Md.: Hello and thanks for taking my question.
Due to a nearby tree that was removed, my shady fern garden has now become an afternoon sun garden. Should I move the ferns to another shady area?
Adrian Higgins: Yes. Or make sure they get heapings of water this season.
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Fairfax, Va.: Hi Adrian,
At a cost that made me blanch, one of our neighbors had to have the water pipe from the street to their house replaced because tree roots had gotten into it.
Can you tell me what kinds of trees pose the most problem for this? And should I remove the crape myrtle that I planted about 4 feet from our water pipe? Thanks!
Adrian Higgins: I think the crape myrtle should be all right. Trees that seek out water pipes: willows, poplars, birch, silver maple.
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Columbia, Md.: I wrote before about growing in hanging bags, the sturdy green grow bags sold online. So far, I have several planted with strawberries and pansies and they look promising. Question: would the standard 20" high 9" diameter bag be able to handle a cherry tomato plant? These bags can be a solution to groundhog and space problems so I hope to one day find them at the local home improvement store. Thanks!
Adrian Higgins: Yes, I think a bag that size would handle a cherry tomato, but be ready to provide some serious support for the vine.
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Just Moved Back To Arlington: Hi there -- Just in from digging in my 2.5 year neglected garden (I've been out of the country). I am having to dig up everything in the beds because it has almost completely converted to weeds. The way I am doing this is using a pitchfork (I think that's the right tool term) to loosen the weeds, then I lift up the plant and shake off all of the dirt, placing the weeds and roots in a large trash can. My question is this -- is there an easier/better way to do this? Can I mulch the weeds, or should I simply put them out with the trash? There's really a lot here so I'd love to do something besides stick them in plastic bags. I understand that I am late to do much this year, so I'm not in any hurry... Thanks!
Adrian Higgins: Hand digging is the most effective. The key is to have something ready to fill the void, or the weeds will soon return. The thought of returning to my garden after more than two years sends a chill up my spine.
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Washington D.C.: I hope you can help (or a another reader). I have noticed a lot of small gnats (I think) in my bathroom and living room ever since I brought two potted plants into the house (an orchid and peace lily)... one of each in each room. I have no idea where the flying gnats are from, I don't have pets and the windows are closed. Would these be coming from the plants somehow?
Adrian Higgins: These may be fungus gnats, which are associated with over watering of plants. You could put down a thin layer of gravel over the potting mix, to reduce this problem.
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Rockville, Md.: When is the right time to trim/shape azaleas? I have 3 plants that are flowering currently. They are healthy and growing nicely, but could use some shaping. However, I don't have a clue when the proper time to do that would be. Can you enlighten me please?
Thanks.
Adrian Higgins: You can trim azaleas after flowering. Do it before June.
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Hardy fuchsia: I lost my head and ordered a hardy fuchsia that was on sale. I live in Ellicott City, have clay soil that I'm busy amending, and everything from full sun to full shade. Where should I put it when it arrives?
Adrian Higgins: I think I would put it in a pot. Most fuchsias really hate our warm summer nights and are prone to rot diseases. Perhaps in a pot you can put it were it will be cooler and in a place that will have some air circulation, perhaps near the heat pump, for example.
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Hollies: Generally speaking, are hollies prone to diseases or pests? We're thinking of planting some soft touch and false hollies. Will they do well in our area? We are indifferent about fruiting -- should we care or is that an aesthetic quality?
Adrian Higgins: A false holly may be osmanthus, which is pretty disease and pest free. The major pest of holly is a leaf miner active at this time of year.
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Washington, D.C.: Could you tell me the proper way to harvest basil -- taking off lateral stems, main stems or leaves? When I remove the main stem, it always seems to die back. Thanks
Adrian Higgins: You should remove a stem just above a pair of lateral leaves, this will promote bush regrowth.
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Germantown, Md.: I'm new to keeping flower beds, and last year I experimented by leaving the mums I planted in September to overwinter. I now have happily growing green plants, but I keep reading conflicting advice. Some say to pinch back the sprouts at 3 inches and some say 12. Some say it isn't necessary. Do you think I'll get flowers from these plants (I just picked them up at Home Depot last year)?
What does pinching back really mean, anyway?
Adrian Higgins: You will get flowers, but they may be later than when you first bought them due to the vagaries of greenhouse production. Pinching them back will promote bushiness and prevent the mums from flopping. I would do it now and again in a five or six weeks, trimming each stem by about one half.
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Washington, D.C.: My climbing roses have blackspot (diagnosed with your kind help last week). Is it appropriate to cut back canes where the majority of the leaves are diseased, or is it better to simply pick off the leaves? I am doing my best to pick up everything that's falling to the ground, and have sprayed.
Thanks for your advice!
Adrian Higgins: Unless it is badly infected, just remove the yellowing leaves. One preventative spray now will work wonders for much of the rest of the season.
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pistachio shells: I'm wondering if I can use the shells from pistachio nuts for drainage at the bottom of flower pots?
Adrian Higgins: Nice idea, I think they might soon turn into a mush from the watering. The beautiful thing about gardening is that you can experiment endlessly and see what works for you.
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Buck Hardy Roses: A friend of mine told me about Buck hardy roses, which she grows in the (very cold) mid-West and I've tracked them down at a nursery in Oregon. Do you know if it's true they don't need herbicide and fungicides?
Adrian Higgins: If I got a dollar for every time I heard a new rose was completely disease free, I'd be on a Caribbean island now pondering the oleanders through my cocktail glass.
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Iowa: Hi Adrian,
We planted a square foot garden this spring and are so far loving the look and also how much easier it is.
We planted garlic which has nice green shoots. Can we re-plant garlic from the bulbs we harvest this year for next year's crop, or do we need to go and buy more bulbs for planting?
Adrian Higgins: You can use them for seed. Folks, we're out of time, please check out the Home section this Thursday and see if you, personally, can reverse global warming.
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