Friday, May 25, 2007

Deer Resistant Shrubs for Zone 5

We are trying to replace a dead Arborvitae hedge (death due to deer browsing) with another non-invasive hedge plant. What would you recommend? I saw some beautiful dwarf quince bushes at White Flower Farm website…do you know if deer eat quince? We are located in zone 5, in Northwestern Ct. and our property abuts a fairly large nature preserve so we do share our land with the creatures who live in it. Currently, the aroborvitae hedge is quite an eyesore as they have been nibbled to brown repeatedly over the past 5 years. What about dwarf lilacs? DO deer like to eat those? The soil is a bit acid due to the dominance of a very large Norway spruce and a very large hemlock.

As I am sure you know, living right near a nature preserve does make the challenge greater and the list less guaranteed, but hopefully I can suggest a few different shrubs that might stand a chance.

I would stay away from quince (Chaenomeles spp.). Lilacs (Syringa spp.) do stand a much better chance, even though some references said to stay away from the cultivar ’Miss Kim’.

I’m glad that you are aware of the threat of invasives and avoid planting them. These deer resistant recommendations I would definitely stay away from: rose of Sharon (Hibiscus syriacus); Russian olive (Elaeagnus angustifolia); and burning bush (Euonymus alatus).

Since deciduous shrubs seem to be ok with you, I would suggest researching these shrubs or small trees:
smoketree (Cotinus) – prefers sun, a great plant for the foliage color and the plume of flowers
serviceberry (Amelanchier arborea)
shadbush (Amelanchier Canadensis) – both provide a very natural look but can be used as a looser kind of hedging
bayberry (Myrica pensylvanica) – the strong fragrance of the stems and foliage deters deer very well in my opinion
St. John’s Wort (Hypericum spp.) - make sure you pick a species hardy to zone 5
cinquefoil (Potentilla spp.)

Regarding evergreens, consider:
leucothoe (Leucothoe spp.) – great woodland option that can tolerate some shade
mountain laurel (Kalmia latifolia) – does best if you have a little elevation to your property
Japanese pieris (Pieris japonica) - I am not sure this is cold hardy enough for zone 5, confirm with your local garden center

Boring Insect Damaging My Lilac

I have a lilac bush with a white flower that seems to have some kind of insect boring into it. I see small sporadic holes towards the base of the trunk and wood shavings on the ground. I applied horticultural oil in the late winter. Can you tell me what it is and what I can do?
Insects often prefer specific host plants from which to feed so it helps a lot to know this is happening to a lilac. Sure enough there is a boring insect that likes to target lilacs, called the ash borer (Podosesia syringae). As you have noticed most damage is done to the bottom 12” of the host plant. For lilacs in particular ash borers prefer feeding on older wood. Let me describe the life cycle because that helps us to figure out the best time of year to go after these damaging insects.

Partially grown larvae overwinter under the bark of your lilac. Eventually the larvae mature into adults and emerge. The adults are brown and black and resemble paper wasps both in size and appearance. In the northeast adults emerge from under the bark in April or May when the weather has warmed over 60 degrees. Usually your best chance of seeing them is in the early morning. In some cases you may even see the pupal skin remaining in the bored hole where the adult emerged. Adult females lay their eggs on the bark of the lilac 4-6 weeks after they emerge. The eggs hatch about one-and-a-half weeks later, and the larvae eventually bore into the bark to begin the whole process over again. Ash borers only have one generation a year.

To best combat them, you want to target ash borers when the eggs and hatched larvae are most vulnerable. Spray the lower portion of the bark with an insecticidal spray in early June and then again four weeks later. This will give you the best chance of killing the exposed eggs and larvae before they get a chance to bore and hide under the bark again. As far as the rest of the year, continue to try and maintain as healthy a plant as possible. Mulch your lilac to help regulate fluctuation in soil temperature. If the lilac is older consider supplemental water and fertilizer to help reduce the amount of stress on the plant.

(for this and many other insect questions I turn to Garden Insect of North America by Whitney Cranshaw, a tremendous reference book. This book is available to view and read any time at our horticultural library located at 148 W. 37th between Broadway and 7th Avenue.)

Thursday, May 17, 2007

Douglas Fir Bark for my Cymbidium Orchid

I am a recent owner of a large cymbidium orchid which someone decided they didn't want any longer. I found it on the street in a plastic bag. I've researched the internet and see that the potting mix for cymbidiums is Douglas Fir Bark (fine grade). Can you suggest any place in the New York City area where I can purchase a large bag of this medium? I'd like to avoid shipping charges which seem to be expensive.

Congratulations on finding yourself that cymbidium. They can be a great plant. The only catch is that they will require some cooler temperatures come fall but we can revisit that later. Newer cultivars are being bred for better warmth tolerance. Your research and findings are correct. Most orchids we try to grow are epiphytic and need to be in a loose mix of either fir bark or sphagnum moss. Cymbidiums are more terrestrial, meaning they grow in the ground instead of in the crooks of trees, so you can use a fine grade fir bark mix. A few references I checked quickly even said that you can use a combination of fir bark and regular potting mix at a ratio of 50:50.

As to where to find it – are you familiar with the flower district down on 28th Street? Mostly between Broadway and 7th Avenues on 28th you will find a ton of different plant shops that sell everything from mixes to containers to cut flowers. A number of stores carry epiphytic mixes appropriate for orchids. You should be able to find the fine grade fir bark, but if shops only have a heavier grade (aka larger chips) then perhaps think about making the 50/50 mix I mentioned above.

Otherwise: bright light to dappled sun; water once a week. If you can keep it near an open window where it will get cooler at night that is a help too. When planting do not bury the pseudobulbs (the large tuberous stems) too deeply. Enjoy!

GreenBranches Article in the Wall Street Journal

In case you have not yet seen it, there is a fabulous article in the May 17th Wall Street Journal about one our community outreach program GreenBranches. Simply click on, or cut and paste, the following URL to your web browser and enjoy:

For those of you that are members and supporters of HSNY, thank you so much for making programs such as GreenBranches a success. For those of you who are not members but are interested in supporting us as we strive to green and brighten local communities all over the city, we ask that you become a member today. Membership information and a secure membership form can be filled out at:

Thank you!

Friday, May 11, 2007

A BASIC Guide to Understanding a Bottle of Fertilizer

Have you ever noticed that every package of fertilizer (“plant food”) somewhere on the label has listed three numbers separated by two hyphens? After years of answering people’s plant questions it still amazes me that most people have no idea what these numbers represent or what it means for their plants. Therefore, here’s a brief tutorial about plants’ nutrients requirements and what you should know when buying yourself fertilizers.

All plants rely on certain macro- and micro-nutrients to live. There are a total of six macronutrients. Three of these are readily available in nature (carbon, oxygen, and hydrogen), and three we usually have to provide as a supplement (nitrogen, phosphorous, and potassium). The three numbers on any given bottle of fertilizer are referred to by horticulturists as the N-P-K. These numbers refer to the percentage of the three different macronutrients present in a single dose of the given fertilizer. The first number is going to be the percentage of nitrogen in a single dose of the fertilizer. Nitrogen is responsible for helping a plant to maintain its lush green appearance. For foliage plants especially you want to make sure that they are getting an adequate dose of nitrogen during their active growing season so that they produce chlorophyll and photosynthesize as optimally as possible. The second number is the percentage of phosphorous. Phosphorous is the macronutrient most responsible for flower and fruit production. If you look at a “bloom booster” fertilizer you will typically see that they have a higher middle number. You might also find that orchid fertilizers have a higher percentage of phosphorous as well. In order to flower, orchids and other plants must use a lot of energy to produce their flowers and attract their pollinators. After the flowers pass, these reserves of nutrients need to be restored. By fertilizing your houseplants or containerized annuals during these active growing months from spring to early fall you can be sure that they are getting the right nutrients to keep putting out a prolific bloom. The last number to discuss is the percentage of potash, potassium in a form that can be readily taken up by plants roots. Potassium helps a plant to maintain overall cellular strength and rigidity, from its roots all the way up to its outermost stems. When trying to establish plants in containers or the landscape, you want to make sure that they have an adequate amount of potash so they are strong and able to deal with all the natural elements they will be exposed to. You will also find that cacti usually like a fertilizer with a decent percentage of potash which makes sense because they are usually pretty firm and rigid to be able to stand up to the pounding of the suns rays.

I hope this helps you to be more of an educated consumer. As I said, this is a very basic overview. If you are curious about soluble vs. insoluble nitrogen or other specific topics feel free to email me your questions. To best care for your plants do a little research and find out the best time to fertilize. Most plants benefit from being fertilized during the active growing season, from spring through to early fall, but should not be fertilized through the colder, darker months. A “Balanced” fertilizer has equal portions of nitrogen, phosphorous, and potassium in a single dose and usually can be used for a number of different houseplants. Some plants, like succulents and cacti, may prefer a lighter application, so again, do a little research. For orchids, many experts suggest applying your orchid fertilizer “weakly weekly” to provide a small boost of nutrients at all times. Follow the instructions and never apply a fertilizer more concentrated then suggested on the label. Excess fertilizing can lead to buildup of soluble salts in your containers or your turf and this can hurt a plant just as fast as you’re trying to help it.

Monday, May 7, 2007

Small bumps all over my cherry trees, Manhattan, NY

I have on my rooftop terrace two purpleleaf sand cherries, or Prunus x cistena. They have been on the terrace for well over 10 years and have held up very well. This year I have discovered tons of small dark bumps and a clear sappy liquid all over the branches and stems of these trees. There is also some dieback on the upper branches, but I know the containers are an adequate size. I rubbed the bark and realized that I can dislodge these bumps with my fingernail. What is this issue and how best do I treat it?

Prunus x cistena is one of my favorite small trees for its rich reddish purple foliage and fragrant spring flower. From my experience with this tree, I know that they are victim to a number of insect pests. In this case, the tree is infested with an insect called scale. There are both “armored” and “soft” types of scale insects. Typically the adult forms of scale insects are surrounded by a hemispherical oval covering that protects them. They insert their piercing, sucking mouthparts into the phloem sap of the host tree and feed off of it, thus producing large amounts of clear, sticky honeydew on the stems. Eventually the adults lay up to hundreds of eggs. These eggs hatch and the “crawlers” emerge, eventually finding sensitive parts of the host plant on which to feed. There they mature into adults, overwinter on the stems, and repeat the cycle.

To best control scale, you need to know the type of scale as well as the timing of its different life cycles. Because many scale are very host specific, you can usually narrow down the list my knowing what kind of plant they are feeding on. In this case I am guessing that the scale in question is called a European Fruit Lecanium (Parthenolecanium corni). I have found that these are a soft-bodied scale, apparently native to North America despite their name, and enjoy feeding on a wide range of ornamental fruit trees. The best time to treat scale is when the adults give birth to their many fragile crawlers. In this case I have researched to discover that the females’ eggs hatch in late May or early June. As crawlers emerge and spread out in June treat the entire tree with an application of Horticultural Oil. Horticultural oil coats and suffocates soft bodied insects and helps to control infestations. Before treating you can confirm the presence of the crawlers by shaking the limbs over a clean white sheet or piece of paper and looking for the mobile young. Treatment of horticultural oil is not considered effective on adults because of their protective covering, so the best option to remove adults is to do so by physically removing them. A coworker passed on to me that using a tooth brush and a mixture of baking soda and water usually works to scrub away the adults, even though the task can be rather tedious.

HSNY Children's Learning Garden at Stone Public Library, Brooklyn

On Thursday, May 3, 2007 The Horticultural Society of New York together with the City Gardens Club of New York dedicated the newest GreenBranches Learning Garden at Stone Public Library in Brownsville, Brooklyn. The creation of a beautiful garden space at the Stone Avenue Branch marks the second time in four years that The City Gardens Club of New York City and The Horticultural Society of New York have collaborated together on a major project.

Opened in 1914 as the Brownsville Children's Library, the Stone Avenue Branch of the Brooklyn Public Library was the world's first library devoted exclusively towards young readers. The Horticultural Society of New York began the GreenBranches program in 1996 because it recognized that the outdoor space around libraries in New York is an unrealized resource for creating green space in urban areas and teaching neighborhood communities about the natural world around them. GreenBranches designs, installs, and maintains high-quality gardens around branch libraries in neighborhoods in New York City. The designers are sensitive to the architecture and history of the neighborhood and work with the local community to include their ideas in the garden design. Designs incorporate hardy, drought-resistant and low maintenance plant material to ensure the longevity and sustainability of these gardens and provide years of enjoyment for the local community. After installation, HSNY continues to maintain and provide educational and healing programs in the gardens for children and adults of all ages.

to learn more about GreenBranches, as well as our other community outreach programs, visit our website at

Wednesday, May 2, 2007

Browning Evergreens in Containers in Brooklyn

My husband and I bought two potted evergreen trees in December of 2006 for Christmas and are trying to maintain them on our deck in Brooklyn with little luck. Right after the snow we noticed the trees started to turn brown and loose their needles. One tree lost a lot of needles very rapidly. The other maintained most of its color and most of its needles. Three weeks ago, in order to try and resuscitate the first and prevent further damage to the other, we decided to replant both in slightly larger pots. We have been watering them at least twice a week and adding Liquid Grow Plant Food. It seemed to help during the first two weeks. The tree with the most damage was almost completely brown and then it made a slight come back with some small patches of green...a small victory for us. But presently it hasn't restored fully and stopped improving. The other tree is doing better than its neighbor. It is 95% green. The browning is in patches at the bottom of the tree. They both get the same amount of sun light from the North East and I still water them at least twice a week although these last few days I didn't because of all the rain. Is our little brown tree too far gone to make a come back and what can we do to make sure the same doesn't happen to our other? Any advice you can give us would be much appreciated.
What you have in your containers are two dwarf Alberta spruce (Picea glauca ‘Conica’). As you see them all over the city, they are popular ornamental trees for containers because they are slow growing and hold that very formal, conical shape. They require full sun and, especially in a container, supplemental water.

Looking at your pictures, I am sorry to say that the one on the left is not going to come back for you. Of course there are always exceptions in the plant world, but to generalize evergreens do not bounce back as easily as deciduous trees, shrubs, or perennials. For deciduous perennials, trees, and shrubs, there are dormant leaf buds that can sprout and provide foliage even after a plant has been cut back. Evergreens grow from their tips out, and usually do not have the same kind of dormant buds. Some evergreens can be pruned lightly to push out more new growth, but by and large evergreens will not put out new growth on a branch that has already dies back.

Therefore, the tree on the left is not going to bounce back – it is best to simply start over. As far as the one on the right, you can prune off the brown branches at the bottom, because again, they are not likely to needle-out again. Evergreens, again, in general, naturally prune themselves from the bottom up if they are under stress. This is typically a response to not getting enough sun – and I have seen it happen on Alberta spruces plenty. Keep it in as sunny a spot as possible, continue to water regularly, and hopefully you will not loose any more of the needles. Next, look at the tip of the branches. If you have new green foliage emerging from the tips then you can rest assured that the tree is still healthy and going to do well this summer.

As far as what killed the other…? It could have been not enough sun. It could have also been not enough water, because you really have to keep containers irrigated constantly. Lastly, reexamine the space. Sometimes there may be a draft or an exhaust fan that we don’t pay attention to that is drying out a plant and/or container faster than we realize. Without being able to see the space, I would go back to guessing it is mostly a sun issue, and even though it may be bright, sticking a plant in that corner might not be the best option unless you know it to be more shade tolerant.