The Garden Plot
Hosted by Adrian Higgins
Washington Post Garden Editor
Thursday, March 2, 2000; 11 a.m. ET
Adrian Higgins is online today to field your questions and comments concerning gardening and horticulture.
Got a chronic case of green thumb? Like getting your hands dirty? 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."
Here is today's transcript.
Can I plant peas right now? I know they like the cool weather and we have been having milder temps lately here in Mass.
Adrian Higgins: In Massachusetts you might want to wait another week or two, but then plant away. You could use the interim to turn the soil and add some humus amendments. Peas, unlike other seeds, are not thinned as a rule. They also require some support. You can create a trellis from bamboo stakes and plastic netting stapled to it. Use tent stakes to secure the bottom of the net to the soil. Then use a pencil or your stout finger to drill two staggered rows at the base of the trellis. The holes should be about two to three inches apart, and each receives a little dried pea seed. If you have not grown peas or beans in the soil before, you might wish to add a black powder called legume inoculant. This promotes development of the good bacterium that peas need to form nodules on their roots, and take up more nutrients and fix nitrogen into the soil. Because you have a long cool spring in Massachusetts you can pretty much select any pea variety that takes your fancy: Late season varieties will mature in time before the hot weather sets in. The mistake most people make with peas is in not setting enough. By the time you harvest the pod and eat a few of these sweet jewels, you seem to have too few for the table. Good luck.
The weather is getting warmer and I'm trying to figure out what to "cut back" and prune and what to leave alone. Can you give me general guidelines--both on shrubs and perennials?
Adrian Higgins: Generally, shrubs and trees should only be pruned for a specfic reason: dieback, or to improve air circulation, for example. Trees and shrubs are best shaped when young. If you have a tangled, overgrown tree or shrub, you can do what is called rejuvenation pruning. You remove entire stems back to main branches rather than shear the bush. Do not remove more than one third of the shrub in any one year. A classic example of this would be the forsythia, which needs rejuvenating pruning every few years because its habit is so thick. But you would wait until after flowering to do that.
The general rule of thumb is that shrubs that bloom in the spring are flowering on buds set the previous fall, so any pruning now would remove blooms. (This may be necessary if you are trying to reclaim a bed and an azalea, say, needs cutting back in order for you to replant the bed this spring). Plants that bloom in the summer flower on new wood and can be safely pruned and shaped now. These include crape myrtles, buddleias, rose of Sharon, vitex, and smooth and PG hydrangeas. Generally, if you do cut these plants now, the height of the shrub will be diminished but the flowers will be much larger. As for perennials and grasses, their dead top growth can be removed now if you have not done so already.
I have a very large maple tree in the back yard and the roots are pushing above ground. This makes it hard to mow over those coming into the grass area and hard to walk back where I don't have grass. Should I put dirt on top of them or what? Thanks.
Adrian Higgins: If it's a silver maple (the worst) or a Norway maple (the second worst)trying to plant beneath them is an endless and frustrating exercise. This is what happens: You put a nice layer of thick soil and mulch beneath the tree, put in shade tolerant plants such as azaleas and cherry-laurels, and they do well for a while and then shrivel and die. Why? The roots of the maple have found this delicious soil and your dutiful watering and simple grown into it, sucking out all the goodness for the other shrubs. You have three choices. You can actually give up on growing anything beneath the tree and sweep away the soil, gently, to reveal the branching pattern of the surface roots. This can be beautiful in its own right and you might be able to plant some tiny bulbs within the crevices, such as scilla or chionodoxa or snowdrops. Secondly, one of the hottest trends in gardening today is the use of tropical and other flamboyant annuals in large pots. These sit above the roots and do not become their victim. Get the largest pot you can afford. As much as I love natural terra cotta, there are some extremely convincing poly pots now that looked like Italian clay ware and are lighter and frost proof, meaning you don't have to lug it in in November. You will need to select plants that do well in shade, things such as gingers, taro (colocasia or elephant's ears), caladiums, helichrysum, and a host more you will find at the garden center in April and May. The third option is to chop the tree down.
Can I move bulbs that have already started to sprout? I put them in an out-of-the-way spot last year and forgot to move them back in the fall. They're about 2-3 inches out of the ground.
Adrian Higgins: Yes you can do, fritillary don't transplant well but most others do. You have to realize that the bulb now has a healthy root system beneath it and you will have to be careful in excavating the bulb not to damage the roots. Once the bulb is in the new location, water it, using a bulb food dissolved into a solution.
I have some out-of-town guests coming in April who are keen gardeners. Can you recommend any good public gardens in the area that we should visit?
Adrian Higgins: Dumbarton Oaks; Tudor Place; National Arboretum, Green Spring Gardens Park, Alexandria; Brookside Gardens, Wheaton. Look too for garden tours listed in the Home section. The Virginia Garden Week is April 22-30, when many fine private gardens across the state are open to the public. While in Georgetown, try Oak Hill Cemetery, really quite good in dogwood season.
My tulips and hyacinths are budding and blooming already due to the changing weather we've been having here lately -lots of rain and 60 and 70 degree temps.- Please tell me what I can do to save my flowers?
Adrian Higgins: What do you mean save? They are supposed to grow and set bud in late winter so that they can bloom in March and April. The mild weather will hasten their appearance. When they bloom they will take a few degrees of frost. The only danger is when they are just on the verge of flowering and we get a hard freeze. This is a rare occurrence, but if it is in the offing, cut some stems the evening before the hard freeze and enjoy them as cut flowers indoors.
I have a large garden plot at a community garden here in D.C. I was so busy at the end of last season that I didn't pull out any of the old veggies, I just let them die off. How do you suggest I start this year's plot?
Adrian Higgins: If the veggies are beans, tomatoes, etc. just pull up and bag the dead vegetation. If they are root crops such as carrots or onions, dig them out and discard.
next, take a sharp hoe and weed out all the young and flowering winter weeds. On the cleaned plot, take 40 pound bags of peat moss or rotted compost (not top soil) and spread them about the plot, maybe one bag for every six square feet. Then take a shovel or garden fork and turn the soil, starting at one side and working to the other end. Do not tread on the newly cultivated soil. Once you have done that, take a hoe or a rake and do some fine grading, to avoid low spots where water will sit. Your plot is then ready to go. When you sow seeds, do so in a way that avoids stepping in the soil (I use a plank if I have to get into the garden). Keep the weeds at bay. Get sowing.
Chevy Chase, DC:
I would like to plant a native rhodo -approx. 4-5 ft. high- this spring to go with some others in my front yard. When is the best time to plant and where are these plants available in our area?
Adrian Higgins: Most rhododendrons sold today might have native blood in them, but they are hybrid of many species and varieties. This is difficult territory for rhodos, I have listed varieties that do well in our region in The Washington Post Garden Book. These include Disca (white); Cadis (pale pink) and GiGi (rose red). It is important to get a named variety that is proven in our region. Rhodos need acidic, evenly moist soil with their feet in shade and their faces in the sun.
A tag along to your response re: Silver Maples
Assuming the tree is healthy and well-estab., is there any harm in cutting the roots that have invaded my raised beds -the beds are well beyond the drip line-? Thanks
Adrian Higgins: These are the feeder roots you normally wouldn't want to damage but in the case of the silver maple you can't really hurt the tree and it's a catharsis for the gardener. Know though that the roots will grow back.
I am a relatively inexperienced gardner living at a rented property that I will be leaving next fall. I would like to plant a ground cover under some bushes out front. I need something that spreads quickly, grows in moderate sunshine, and is inexpensive. If it doesn't come back, that's ok! Keep in mind I live in Michigan. Any suggestions? I need something easy! Help!!
Adrian Higgins: It sounds to me you should wait until after frost season (late May for you?) and plant an annual that will fill out and do well. Impatiens, madagascar rose periwinkle, petunias, nasturtium: The world is your oyster.
I have lived in Northern Virginia all my life until 2 years ago, when we moved to Alabama and this is my first dealings with Bermuda grass. Is there anything I can do to get rid of the onions that constantly appear. Nothing seems to work. Regular weed killer works wonders on other weeds, but does not affect the onions what so ever.
Adrian Higgins: The only effective way I know of removing them is to wait until after a good soaking rain and then take a fish-tail weeder and dig out the clumps by hand.
Are African violets best kept just as the little potted plants they are sold as, or can they be planted outside?
Adrian Higgins: I have not seen them planted in the garden. They are obviously tender plants and also prone to sun scorch--I don't think they would be successful outdoors, maybe someone out there has tried them. Another problem with African violets is that droplets of water cause leaf scorch, obviously this is something you cannot control outdoors.
Silver Spring, MD:
Why do seed companies distinguish between Regular Leaf and Potato Leaf varieties of tomatoes? Thanks
Adrian Higgins: I don't know, I think it's just a decription. Tomatoes are in the same botanical family as potatoes, so I imagine there are some strains that have leaves that look like their cousin. The more important distinction with tomatoes is whether they are determinate or indeterminate. The latter take longer to fruit, but then fruits continuously through September.
I live in a townhouse with a very small yard that fortunately adjoins open common grounds. I would like to plant a small, specimen tree to set off the lanscaping in the back. Can you recommend some small trees, specifically anything that doesn't get more than 15' tall and spreads no more than a few feet? I've looked into the ubiquitous Japanese red maples, but all of the short ones will eventually spread up to 20 feet or more! -Thus taking over the entire yard.- Thank you so much for your help.
Adrian Higgins: My favorties are Sargent's cherry, cherry Hally Jolivette, or certain varieties of crab apples (as with rhodos, you have to be discerning for success in Washington). Upright Japanese maples are fine trees, yes, they do in time reach 20 feet high or more, but that would take at least 15 years--something to consider. Another great small tree is the American hornbeam.
I have a Japanese Maple that was there when I moved into my home, and I know almost nothing about how to care for it. I tried to water it regularly last summer when we had so little rain. In the fall, the leaves turned red, then dried up. I assumed this was normal, but now I am worried. Am I supposed to cut it back? When should I expect to see new growth. Any advice would be appreciated
Adrian Higgins: There are two basic types of Japanese maple, the upright forms addressed in the previous question, and the weeping, threadleaf types. They do benefit from shaping and thinning, but this is quite an art: it should be done now. If you don't feel confident of your skills, leave it alone. Look for pruning classes listed in the Home section. This spring, the buds will break and the leaves will regenerate, unless, of course, the drought did in the plant. You cannot tell now readily, new growth will emerge in April. Be patient.
My wife asked me to spray dormant oil on our fruit trees and roses. Can you explain what this oil is and does?
Adrian Higgins: Oil is a non toxic and highly effective pesticide. It literally smothers the eggs and overwintering larvae of such insect pests as thrips, scale, mites, and adelgids. You should apply it now before bud break. Temperatures should not dip below 40 degrees for 24 hours after spraying. Make sure that you cover all the stems and, on evergreens, the leaves or needles. You may need a step ladder to reach higher areas. I use a 1.5 gallon hand held pump sprayer (the oil is diluted in water).
The tulips I planted a few months ago are starting to bloom, about 2 inches are showing from the ground. Do I need to put anything over them or on the ground to keep the squirrels from eating them?
Adrian Higgins: Possibly. I have seen squirrels dig up and eat emerging tulip bulbs. I wouldn't do anything unless you see the rodents doing this. If they do, cover the tulips in a plastic net mesh, being careful not to damage the leaves.
I have a lawn question for you. After years of desparately trying to renovate a weed-filled lawn, I have decided to take drastic measures. First, replace about half of it with ground covers. Second, replace what's left with a-new sod or b-a zoysia lawn. Which one should I pick? I admit I like the deep green color of regular grass, but I can't ignore the easy maintenance of the zoysia lawn. I would rather concentrate my limited gardening time on my flowers and veggies, so I need a lawn that's easy to maintain. Your advice is much appreciated!
Adrian Higgins: The choice is yours. Personally, I don't like zoysia grass. It turns brown for half the year, it is expensive to install, and it spreads to areas where you don't want it. But it is a boon in the long summer months.
Silver Spring, Md.:
When can I fertilize raspberries and roses and what material shall i use?
Adrian Higgins: Roses can be fed now, using a slow release granular nutrient formulated for roses. I am a big fan of using kelp or fish emulsion fertilizer on roses, they respond with tremendous vigor and they seem to be more disease resistant. As for raspberries, be careful not to overfertilize or use a feed high in nitrogen, this will diminish flowering and fruiting. If you have raspberries, put Elmer's glue on freshly cut rose canes to prevent raspberry cane borer from entering the rose stalks. I am afraid our time has come to a close. I know there were a lot of questions today and I couldn't get to all of them. But I thank you for your interest and hope you enjoyed the chat. My colleagues will be back next Thursday at 11 a.m. (I'll be in England, viewing gardens, what else?)
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