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Ask Gardening123 - April 2001

by Gardening123 Staff

Each month Gardening123 will publish questions from users here in the “Ask Gardening123” section and answer them. These questions can pertain to gardening or they can be technical questions about the site. If you have a question you would like answered please email it to

My backyard garden borders a small side street. Recently, a streetlight was repositioned so that it's full light falls on my garden at night. This is most annoying to me, but what I really need to know is - will it affect my plants?? I have annuals, herbs, perennials, a few roses, woody shrubs etc. I don't feel I can fuss at the city without some ammo and if it's going to affect my garden, that's all the ammo I need.


Lengthened daylight can affect several garden plants, especially those that customarily come into bloom in autumn as day length shortens. Chrysanthemums, Salvia madrensis, and S. leucantha, Mexican mint-marigold (Tagetes lucida), candlestick tree (Cassia alata), Angel's trumpet (Brugmansia), shrimp plant (Justicia brandegeana), and others might be inhibited from bloom by continuous night lighting.


The previous owners of our home did some landscaping before the home was placed for sale. They planted three cryptomerias on the East side of the house. As the house gets no shade and faces South, the sun is brutal on our wood, so we have planted a number of trees on the property. In a few short years, the cryptomeria and the trees will be in competition, especially visually. While I would like a pyrimidal evergreen where they are located, their size is too much. Can they be pruned to a max height of 7" and shaped, or must they be removed? There is no where else where I would want to move them.


From what you've said, it sounds like you have a Cryptomeria japonica. This is the most common form of this species. This type will usually reach 50-60 feet tall over about a 20-30 year period.

It also sounds like the tree is already over 7' tall and you want to try to cut it back. This could end-up being a constant battle for you if you decide to keep it. These trees were never meant to be small. If you do not want to constantly prune them, you may want to consider getting rid of them altogether before they get any bigger. There are lots of other cone-shaped plants that you can plant in their place. Not only are they going to compete with the trees later, they are going to compete for water this summer and if your new trees aren't very well established, you might have more problems depending on how close they get.

Before we make replacement plant recommendations, it would be good to know your sun or shade requirements and what size space you are trying to fill.

Of course, your other option is to try and cut it back and see how fast it comes back. Sometimes they can grow 6-12" in 5 months.


Do you have a list of trees by rooting characteristics - i.e. shallow or deep rooted? Also which shade trees can be planted near a house without fear of breaking limbs or shallow roots disturbing the foundation?


We are not aware of any list that attempts to classify landscape trees by rooting characteristics, but would note that most trees vary their root growth in response to the soil types and moisture levels under which they are grown; i.e. on heavy clay soils, on waterlogged soils, or on rocky ground nearly all trees develop shallow, widely spreading roots to take advantage of the limited depth of porous soil; on deep sandy or loamy soils many trees develop corespondingly deep roots; bottomland or sandyland tree species such as pecans, walnuts, hickories, mesquites, acacias, pines, and several oaks develop taproots especially adapted for such deep soils.

As far as breaking limbs go, any tree that grows over a house might, under stress, fall on it; but, if we had to choose, we would go with an oak and not lose too much sleep over the possibility of it breaking. Ordinarily, only trees with massively buttressed trunks such as American Elm would pose a significant threat to a foundation, but it would certainly be prudent to space any shade tree at least 6' from a concrete slab, if possible. Palms, bamboos, hollies, magnolias, callery pears, and narrowly upright conifers like Eastern red cedar (Juniperus virginiana) or Italian cypress are often planted flush to foundations without ill effect.


How can I control clover in my lawn?


First, you will have to pull or dig up the clover that is already in your lawn. Fertilize your lawn on a regular basis (at the recommended rate for your particular type of grass) to keep it healthy and discourage clover from growing. Mow often to prevent self-seeding. Otherwise, in the spring and early fall, treat your lawn with a weed killer from your local garden center. Repeat treatments are often necessary


Could you please tell me the names of some roses that grow exceptionally well in the Atlanta area?


The following rose varities are great for Atlanta's zone 9 climate:

Rosa x 'Monsieur Tillier: Shrub rose and is totally disease resistant in the garden.

Rosa x 'Park's Tea Scented Yellow: Climber with pale yellow flowers. Blooms once and is as vigorous as a Lady Banks rose.

Rosa "Martha Gonzales": Shrub rose that grows up to 3' with burgundy foliage and crimson flowers.

All of these roses are available from the Antique Rose Emporium at


The leaves on my azalea have turned yellow except for the veins, which have remained green. What’s causing this to happen?


It sounds like your azalea is suffering from a condition known as iron chlorosis or iron deficiency. This condition is usually associated with plants that are growing in very alkaline soils. To correct the problem, try spraying liquid iron on the foliage and on the soil surrounding the plant. An application of aluminum sulfate or lime-sulfur to the soil may also help to lower its pH level. If you are planting an azalea in an area that you know has alkaline soil, try adding a handful of soil sulfur. You may also want to add organic mulch, like shredded oak leaves, or a soil conditioner that can be purchased from your local garden center.


When is the best time to plant ivy and can you give me some tips?


Ivy should be planted in the spring in a shady location that can provide fairly moist, rich soil. Space plants about a foot apart for quick coverage of an area. Be careful not to plant too close to stone or brick walls as the aerial rootlets can cause damage to the mortar.


I have always heard that scratching a poison oak rash will cause it to spread. Is that true?


No. The rash is an allergic reaction to a chemical called urushiol that is present in every part of these plants from the roots to the leaves. Blisters are formed by your body’s immune system as it reacts to the poisonous substance that is absorbed on contact into your skin. The fluid that sometimes leaks from the blisters does not contain the oil and therefore cannot spread the rash. The rash appears to spread because oil from the plant can remain active for one to two days if it is not removed after the initial contact.


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