Horticulture Guy

Q. I received a rose bush for Mother’s Day and kept it in a clay pot on the deck because it is the only sunny spot. Will it survive the winter in a clay pot. Any special precautions? Also, it has had black leaf problem. Will that kill it this winter? Thanks. Maureen - Holmdel NJ

A. It depends how close the pot is to the house. There is always a chance that a clay pot will break if there are freezes and thaws. Unless the clay pot is sealed the trapped water in the clay pot expands as it freezes and can crack the pot. Also see if you can find the USDA hardiness zone of your rose. It may be printed on the label that came with the plant. You can leave plants in containers safely if they are rated for two zones lower than your zone. I would guess you are at a zone 7 (Having grown up in NJ I know you are near the shore). That means a plant rated to zone 5 could be grown in a pot. The alternative is to find a sunny location in the yard and sink the pot in a hole until spring. The black spot disease you have on the roses won’t be active during the winter but the overwintering spores may attack your rose again in the spring. Once the plant is actively growing again can use organic neem oil to control the blackspot.

Q. My neighbor has a lovely red Norway maple. The city inspector wants to cut it down saying it has wilt infestation. To me it looks very healthy. It is about six or seven years old. How does the inspector determine this kind of disease and how can get evidence? I do not want the tree cut if it has a chance to survive. Isabella Kates - Ontario, Canada

A. They have probably diagnosed Verticillium Wilt.  Usually you see outward signs of stress first, like reduced leaf size or wilting of leaves when there is no drought.  The strongest indicator is then looking in at the wood, which usually becomes discolored from the infection.  Your own University of Guelph has a very nice document http://www.uoguelph.ca/pdc/Factsheets/PDFs/007VerticilliumMaple.pdf  on the disease which should help you solve this yourself.  At least you will be able to converse with the city inspector and have some knowledge of what he is talking about. 

Q. It’s my first winter in my new “established” house. Lot’s of free standing bushes which I know all flower in different times of the summer, don’t know what they are but they have become overgrown and I have no idea when to prune them or how much.  There are forsythia, taller then a person and the two other major bush growths are 15 to 20 feet high and I would like to get them down to about 5 ft or so any suggestions, based on the info I have provided?  Thanks Sandy - Vernon CT

Without knowing what the other species of shrubs are it is difficult to tell you how to prune them and what type of pruning (e.g. drastic) they will tolerate. Many shrubs have their own genetic predispositions.  I can say that if they are flowering shrubs and you do not wish to loose a season of blooms you will want to prune early blooming shrubs immediately after they bloom since they bloom on old wood where flower buds form.  Later blooming shrubs have a larger pruning period, which includes the dormant season, since the flowers will develop on new season’s growth.  Your forsythia will take some heavy but judicious pruning.  It flower buds grow on old season growth so take that into consideration when pruning.  I would suggest either finding a book on pruning shrubs or checking out the University of Connecticut’s Home and Garden Education Center website: http://www.ladybug.uconn.edu/ for more information.
 

Q. I have an apple tree about 15-20 yrs old. It bore lots of healthy fruit, but I couldn’t reach 3/4 of it. I don’t think it has ever been pruned. I know which limbs to take out, but how aggressive can I be, and when should I prune? Also, can I cut back the length of the branches, or the height of the tree? I miss your column, but am glad to find you online. Thanks! Marty Fisher, Orting, WA

A. Actually you can be fairly drastic especially with any vertical growth but as you guessed timing is important.  Since you seem to be familiar with what the shape should be (I know which limbs to take out) I’ll just reiterate for others that may read this.  The best shape for the apple is to have an open center.  So your goal is to open up the center and thin things out so that light can get into the center of the tree. Pruning now would likely result in loss of fruit this coming season and possible overgrowth of new shoots since the tree will have the energy it would have used on fruit production on new excessive growth. Vertical branches bear less fruit than more horizontal ones so a few of those could be removed now in the dormant season. I would wait until you see the fruit set in the late spring and then go in and get that tree back into shape being sure to leave a crop of apples to enjoy.

Q. Yes I miss your column. I’m looking for recommendations of native trees to plant on our parking strip, which is on the North side of the house.  These are to replace the two matching winter flowering Japanese flowering ones I need to have removed because one has died. I think natives will have a better chance. Lily Warnick - Gig Harbor, WA

A.  Well since you say that the strip is on the north side of the house I will assume that it is either a shady or partially shaded area, which limits the number of native trees that would be appropriate.  If you would like to stay in the cherry genus there is a native Bitter Cherry (Prunus emarginata var. mollis), which may be suitable.  Be sure not to get the “var. emarginata” which is more spreading and shrub like.  Although the flowers are not quite as showy the Cascara or buckthorn (Rhamnus purshiana) is another option if the soil is on the moist side.  A Pacific Dogwood (Cornus nutallii) is another showier alternative although it is somewhat susceptible to the fungal disease anthracnose.  Breeders are actively working on disease resistant varieties of this. 

Q. I have a 6-foot laurel hedge, which is about 35 years old. Over the past year, the leaves in various areas of the hedge have suffered from a fungal/mildew problem. On advice from a local gardening specialist, I sprayed the leaves with something they recommended. This temporarily alleviated the problem but over the weekend when I was clearing out the plants around the hedge, I noticed that there were a lot of leaves lying under and along the base of the hedge.  When these were all cleared out, it became apparent that some of the branches at the bottom were rotten through. They didn’t even need to be cut, they just snapped, despite being very thick. It now seems that the stems with this problem are the ones which have all the diseased leaves - hence the randomness of the leaf problem. All growth for about 2 foot from the bottom has now been cleared and the worst of the rotten wood removed. The majority of the hedge is healthy but it now has some gaps! Will the whole hedge die? Given that it is November and the onset of winter, it wasn’t a good time to prune it, but I thought it would be better than leaving it. The base is now clear and air can circulate. I live on a very busy, noisy road so can’t be without my hedge as it provides a vital sound and privacy barrier. Should I take it all out and replace it with the largest replacements I can buy or should I leave it and see if it survives and grows back? Your help/advice would be much appreciated as, due to the time of year, time is of the essence! Charmaine - United Kingdom Many thanks.

A. Although English Laurel (I assume it is English since you are from the UK and probably don’t call it English Laurel there) is quite disease resistant wet conditions can create conditions ripe for bacterial and fungal infections.  In this case it was probably one of the rotting pathogens like Fusarium, Rhizoctonia, or Pythium.  These can attack both roots and stems.  Your instincts were good, as cleaning diseased wood should be done as soon as you find it.  The key is to cut back into clean disease free wood if possible and clean your pruning equipment between each cut to prevent spreading the disease.  These Shrubs are very resilient but you will need to address the air circulation and also determine if the soil stays overly wet which will exacerbate the situation.  I would see how it fares over the winter.  You may see new growth from the root system.  In the future in addition to normal hedging (which concentrates the growth decreasing air circulation) you may also want to do some modest thinning. Let me know how things progress.

Q. Peter, I dug up irises from a bed over-run with grass, with a grand plan for making a raised bed lined with landscape cloth to keep the grass out, but what in the world should I do to keep the irises alive until hubby makes that bed for me? Keep them- not him- out in the air? Stick them in perlite? Plant them somewhere else for a while? Have I killed them? They have been out of the ground for 5 days. Sure would appreciate your words of wisdom. Many thanks! Linda S. - Lakewood, WA

A.   Yes you should plant them somewhere else for a while.  This is called “heeling them in”.  You simply dig a trench in another section of the garden and line them up in the trench at about their same growing level in the grass infested bed and cover with soil until you are ready to put them back in the reclaimed bed. Water them in the unlikely event there is no rainfall.

Q. I own a Dracaena Mass Cane.  It stays indoors in the winter and is brought out in a screen house in the summer months.  It enjoys being outside so much that it now is taller than ceiling height of the house. Question: Can the top be cut back?  It is about 9 ft. tall now.  If I cut it back to say 4 ft. will this kill the tree?  Is there a certain time of the year this should be done? Tony R. - Valley Stream, NY

A.   Yes in theory the canes can be cut back on Mass Cane (Dracaena fragrans ‘Massangeana’) since the plant you now own came from a stem cutting taken from a mother plant.  So in theory you should be able to remove the stem and have new growth form below the cuts.  In theory you could also put rooting powder on the revomed stems, or sections of those stems and start new plants (stripping the leaves off of them when they are removed.  In tropical regions like Costa Rica where they are harvested I believe they propagate all year.  But in NY I would wait until the weather is a little closer to “tropical” and do it in the spring the late spring or early summer.  I have never performed this operation on a Mass Cane myself so this is all theoretical.  Since most plants have multiple canes I would suggest testing one cane this summer and see how it responds.  If you get new growth then you can comfortably prune back the other canes. 

Q. We have an old, large maple tree in our yard.  It does not have as many leaves as it used to.  It appears to be slowly dying.  Many years ago we put a raised rock bed around the tree and planted a few items.  The dirt is about one foot high.  Could that have been distressing the tree over the years?  We plan to knock the rockery bed out and take the excess dirt away.  We’ve also had woodpeckers creating sap drips and wondered if they were causing the problem.  Do you think we can save the tree by taking the dirt away?  Or is it too late?  Thanks, Jan - Tacoma, WA

A.  Yes I believe the raised bed around the tree is exactly why you are seeing a decline in the Maple.  Changes in soil level above trees roots reduce oxygen levels for the root system effectively suffocating the tree.  If the root surface area is large enough will completely kill a tree very quickly.  If the tree still shows signs of life removing the excess dirt may allow the Maple to recover.  The woodpeckers are likely a symptom and not the cause of the Maple tree’s decline.  

Q. We have a Small Leaf Linden tree at our curbside.  It is quite large. 10 years ago, when it was pruned, the leader was cut.  Since then, it has grown into a very huge, very full mushroom shape. 3 years ago, we had it pruned by an expert. Wonderful job.  However, all summer long, small dead branches kept falling off into our driveway.  It is overgrown again and must be pruned again. Hubby wants it pruned and cut way back on the sides and top to make it smaller.  Please advise us for the best time of the year to have it pruned.  Thank you. G. Davis - Philadelphia, PA

A.  With the loss of the leader you now have a large shrub on a trunk.  I am not sure if the person you had prune the tree mentioned about trying to retrain another branch to become a leader and give the tree back its pyramidal shape. This is not essential in this case since the Little Leaf Linden (Tila cordata) can be pruned like a hedge.  Lindens have a tendency to bleed sap if pruned around its growth spurt in spring so avoid late winter through spring for pruning.