AZ Arboretums

Plant Q & A

Q: Would like your advice on a tree that is frost tolerant, doesn't have pods or thorns, compatible with the Surprise, AZ area that stays green year round and doesn't get to large.Your expertise would be greatly appreciated. Sincerely -- Marie

A: Some choices that are usually available are Shamel and Fan Tex Ash, (Fraxinus uhdei and Fraxinus velutina 'Rio Grande') and Fremont Cottonwood (Populus fremontii, male or cottonless variety if available). -- The Plant Man

Q: I have two ficus trees in my yard that have been severely affected by last winter's cold. The entire tree turned brown this year whereas in the past only a few twigs at the top of them would brown. In the past I ignored them and they recovered after quite awhile. Although this year the whole tree turned brown, the main trunks now are exhibiting many new, green shoots and a few of the larger branches leading off of the main trunk are beginning to sprout new shoots. However, many, perhaps most, of the branches and all of the twigs seem to be dead. If I carefully scratch the bark along them, there is only black instead of green. Many of the smaller ones snap off when gently moved and seem dusty, dry and dead.

Advice from sites online so far has been that it is ok to remove any dead branches, but there are so many seemingly dead ones, including some that are substantial in size, that I am fearful of harming the tree if I remove all of them. Might they revive? My HOA loves to micromanage us and has instructed all of us that we need to trim our tress now. It is only a matter of not much time before they begin hounding me about this issue. Several people in the neighborhood have already hired an arborist who has drastically topped their ficus trees. I am determined to avoid this!

I know that ficus trees are not native to Arizona and I did not plant them. However, they are large and do provide very nice and much appreciated shade for us and I would like to try to save them. Can you advise me about what to prune and if a branch that exhibits no green under its bark is truly dead? Thank you -- Bobbie

A: This past winter as you have observed caused extensive damage to many types of vegetation. In particular many ficus were severely affected. Earlier in the season in can be diffcult to tell what is dead as many seemingly dead twigs and branches will sometimes come back to life. However, this late in the growing season (June) it is generally safe to say that any twigs/branches that are brittle and black or dark brown underneath the outer bark are truly dead and should be removed. I realize that this may mean a very large percentage or perhaps even a majority of the branches will have to be removed, but in order for the tree to adequately recover it really needs to be done. If the trees are so badly damaged tthat he structural integrity of the tree is lost you may want to even consider removing the entire tree and starting over again with something else. -- The Plant Man

Q: A few questions, please: We live in the Phoenix area and are trying to decide on which of three trees to plant (Chinese Elm, Mastic, or Brazilian Pepper)-- 1) Is a Chinese Elm (Drake variety) tree deciduous in Phoenix, AZ area? Does it have thorns? If so, is there a variety that does not have thorns? Is it messy? 2) Does a mastic tree have thorns? If so, is there a variety that does not have thorns? Is it messy? Are its berries harmful to dogs (we have a dog)? Is it evergreen? 3) Are the red seeds of the Brazilian Pepper tree harmful to dogs? Does this tree have an unpleasant odor (a park employee told me of this)? Is this tree evergreen or deciduous? Thank you! -- Linda

A: 1. I am not familiar with the Drake variety, but in general the Chinese Elm (Ulmus parvifolia) will frequently turn deciduous in both winter with significant cold and summer if it is under severe drought and/or heat stress. I have never noticed any with thorns. Because of the periodic leaf drop it is somewhat messy although less so than some tree species. 2. More than one species of tree can be commonly called Mastic. Probably the most common for this iasrea is a smaller type of Pistacia. The botanical name is Pistacia lentiscus. 3. The Brazilian Pepper (Schinus terebinthifolius) is normally evergreen year round. It has no particular bad odor that I am aware of. The fruit from it can be somewhat toxic. -- The Plant Man

Q: I am very saddened. Our pretty bouganvillea (sp?)bushes took a beating during the recent frosts, and now retain only dried golden leaves. I read somewhere that if the leaves do not fall, that is a good sign that the tree is still living. Yet, how can new foliage grow when the old continue to hang onto the branches? What can I do to ascertain whether or not the bushes are still alive and to encourage new growth? Do I need to somehow remove the old leaves (shake the bush or prune the branches?) in order to have them fall to allow for new growth? How about fertilization/plant food for the bushes at this time? If so, what type do you suggest? How long will it take to show signs of new growth/flowering once again? Thank you!! -- Linda

A: It is not uncommon to have Bougainvilleas freeze back in the winter even when we have one less harsh than this past one has been. Most Bougainvilleas have survived the freeze, but will need to be pruned back to remove dead foilage and encourage new growth. It is safe to remove dead growth at this time. One thing to look for as to whether or not to be able to discern how much damage has occurred include checking the cambium tissue. The cambium is the tissue located immediatedly underneath the outer bark. Scrape back with a finger nail or pruning shear blade to see if it is a healthy soft textured green color. If it is a dry brown color it most likely will not recover and should be removed. You could spend a lot of time going over this branch by branch, however since Bougainvilleas are such prolific growers a more practical method would be to simply do a "rejuvenation pruning". This consists of cutting back the entire plant to within a foot or so of the ground. Don't worry. If the plant has not been completely killed by the repeated freezes (which is unlikely) in a few weeks or less you should begin to see new growth from the base and by mid-summer you probably won't even to be able to tell it was frozen. Bougainvilleas benefit frtom frequent light fertlliziations so you you could begin at any time. Any type of liquid or granular fertilizer such as Miracle-Gro that is high in phosphorous and potasssium plus nitrogen will encourage both new foliage and flower growth. Again, unlike many plants don't be afraid to over prune. -- Plant Man

Q: Hi - I have a simple question. I have a red bird of paridise plant. I have looked in several different places to find out when I can transplant them. One plant is about 8ft tall and the other is about 5ft tall. Any information would be helpful. Thanks. -- Brian B

A: I would say that probably the late winter/early spring would be best while they are still dormant. I would also recommend cutting them back severely before attempting to transplant. I am also not certain as to how well they transplant, especially plants of this size. You might be better off stating over with smaller container grown plants rather than trying to move these. Good luck. -- Plant Man

Q: We just removed the last of the citrus trees an need to replace them with shade trees that can grow quickly and preferably without to much mess. There is a giant ficus tree in a neighbors yard that seems to be what we are needing, however, we went to a local nursery and the said that the ficus is frost intolerant and a poor choice. Any thoughts?  -- DAAGENT86

A: I am not certain why the nursey said what they did. It is true Ficus are somewhat frost tender, but definitely no more so than Citrus or many others. They also have the ability to normally recover well from light to moderate frost damage. The species that I would recommend as best for this area is Ficus nitida, much more cold hardy than Ficus benjamina. It is normally evergreen, but does have a lot of leaf drop underneath. It also has the ability to take shearing well (unlike most trees) and you can keep it either as a tree, shrub or hedge. An excellent source of other tree species that would be suitable and their characteristics is to be found on theUuniversity of Arizona Cooperative Extension Service web site. -- Plant Man

Q: I have received different and conflicting advice on how to transplant, water and care for ocotillo.  When I built my home, the one ocotillo the landscaper planted died.  My guess is it was not planted in a location where it got full sun, and that it may have gotten too much or too little water.  It also could have been too traumatized or dead when it was planted.  I have purchased 3 more ocotillo from a local nursery and would like your advice on how to plant, water and care for them.  Also, any advice you could give me in selecting "bare root" ocotillo at the nursery would be appreciated. -- Bob N., Utah

A: In selecting bare root Ocotillos make certain that they will take the climate ikn your area. mthey are a true low desert plant and although they can take quite a bit of cold, too much may cause them to freeze out. If they have others in your area that are doing well and have been there for several years or more you should bve o.k. Try to find specimens that have a well developed roots system with a good combination of larger as well as some fibrous roots. The larger roots are necessaruy for mechanical support and the fibrous ones are ijmportant for water and nutrient uptake from the roots. They can normally be planted any time of year, but spring is probably best. Theyneed to be watered in throughly and then allowed to dry out completely in betrween. a small amount of fertilizer added a couple of times a year will help, but be careful not to over fertilize. Like most woody plants they should be planted as closely as possible to the same depth they were originally growing in the desert. Ocotillos actually tend to make more of their growth beginning in the fall so do not be surprised if they may lose their leaves during the hottest part of summer. They should leaf out again by fall. If they do experience a summer leaf drop uyou may want to try increasing the water too them, but be careful not to over do it. Once established after 2-3 years they normally require little extra care. You may also want to research the University of Arizona, Texas A&M, or the Deseret Botanical Garden in Phoenix web sites for additional information. Good luck to you. -- Plant Man

Q: How do we care for Globe Mallow (sphaeralcea ambigua) plants. We have several that are really huge. They must have spread out at least 4 feet. We also have a couple that have stayed small. The large ones really bloomed this spring. Now they look like they need to be trimmed back. How much trimming can they take, and if we do trim them will they come back as full as they were? Also were can I find information on how to care for desert plants?
Thanks --- Jim and Barbara T.

A: The Desert Botanical Garden in Phoenix is an excellent source of information for desert plant selection and care. Also, most bookstores have good gardening sections on desert plants. One book I can especially recommend is Plants for Dry Climates. In answer to your question specifically about Mallow it may be pruned back to the ground and still come up again either from established roots and/or seeds. It is normally so vigorous it is hard to keep it in bounds. -- Plant Man

Q: I have a Hong Kong Orchid Tree that was planted less than a year ago. It appears that I have powdery mildew on the branches and the new growth. I can not find any information on how to treat this on a Hong Kong Orchid tree. I am concerned with using chemicals because of the hundred-plus temperatures. Do I even need to treat this problem? Thank you for any help. -- Gabby N.

A: From the photo you sent it appears your problem rather thatn mildew is actually either mealybugs or scale insects. If these pests are present only in small numbers you may not need to treat at all. However, if they do appear to be adversely affedcting the tree, especially the newre growth you may need to treat. There are at least a couple of different possibilities. One would be to use a commercial prepared systemic insecticide spray which can be obtained from most garden centers and applied on a small tree either with a hose end or hand sprayer. You are also corredt about being concerned with applying chemicals during extreme heat as most insecticides should be applied when it usually 90 degrees or less. Always follow the lagbel directions. At this time of year one possible solution is to apply weither in the evening or early morning. A couple of other possible treatments that will sometimes work if the infestation is not too heavy are either a mixture of rubbing alcohol and water or a mixture of dish sopan and water-about 2 ounces of soap per gallon of water. Either one of these mixtures can be applied with a hand sprayer of small spray bottle. More than one treatment may be for full control. I would also recommend using these homeowners remedies during the evening or early morning hours as well during this time of year to avoid potential burning of foliage. Again, if the infestation is not too severe you may just want to wait. Usually most insects are very seasonal iin nature. so eventually these may go away on their own. Good luck. -- Plant Man

Q: have read your recommended publication from UNCE regarding Chinese Elm and a fact sheet from the U of Florida. I have what I'm told is a Chinese elm in my small front yard (actually 2 - one was a 15 gal size and one was a 24 inch box) which have been planted here since July 2005. I don't know if they are true Chinese elm or Siberian. The larger of the two retained its leaves and was green through most of January but then seemed to start dropping brown leaves by Feb. It has since come back full force with many new branches and dark green leaves abound. The smaller tree lost its leaves early in the winter (I thought it died) and has also come back though not as heartily. What am I supposed to do to prune these trees? The larger tree has branches now close to sweeping the ground and looks “heavy.” The smaller tree has thickened at the top but all the branches go straight up. Both trees are well staked but I am concerned about their vulnerability when the monsoons come. Any advice on how to prune or trim would be great as well as any resources to research. Thank you. - Kim, Queen Creek

A: Both of your elm trees are most likely Chinese Elm (Ulmus parvifolia) rather that Siberian Elm (Ulmus pumila). Siberian elm and other colder limate elms are frequently found in the higher elevations of Arizona, but in the low desert most are generally the Chinese Elm. It would take too long to adequately detail pruning procedcures, but in general trees should be pruned so they do not have limbs crossinig over each other, limbs hanging too low or too dense a canopy. some generally good sources for more detailed information on pruning are from the University of Arizona cooperative Extension Service's on line bulletins. Also, the U of A Master Gardener program for Maricopa County also gives workshops and presentations on this and many other gardening subjects. The are listed in the phone book under Maricopa County Cooperatiove Extension Service and are located near 40th St. and boradway in Phoenix. -- Plant Man

Q:  I need information on how to trim and care for my tree. -- Concerned

A: In general Canary Island Date Palms should be cared for in much the same way as other ornamental palms. Briefly, they neeed sufficient water with drainage, but allowed to dry out for awhile in between waterings. They should have dead and dying leaves pruned off, but not be over pruned as unfortunately is so often done by removing large amounts of
green foliage. As long as the palm is in good health they need little supplemental fertilizer, once in the spring or early summer is normally sufficient for the year. Also, when pruning the dead and dying leaves and a small amount of
green leaves if necessary the flower stalks should also be cut off as well to avoid fruit drop in the case of female palms or pollen dust and litter in case of a male. An additional reason for removing the flower stalks is also to reduce potential nestng sites for pigeons which can potentially become a major nuisance pest. -- Plant Man

Q: Last year one of our hibiscus plants died nearly overnight. It was getting enough water & sun so I thought maybe due to the fact that it was nearly 5 yrs. old that it had come to the end of it's life span in the intense AZ heat. Approx. 2 weeks after the death of this plant; the next hibiscus planted right next to it also died - again nearly overnight and again I did not think too much abt. it. This year one of my Queen Palms which is planted right next to where the hibiscus were, looks as though it's abt. to topple & die. We had the tree trimmers here last week & they said it may be getting eaten by something. My question is this: Is there some type of underground insect in AZ that could be responsible for the death of both the hibiscus plants & now the queen palm? If so, what can I do to keep it from getting to the rest of my trees & plants in that same area? Thank you so much for your help.  -- Patty

A: Yes, there is an underground pest problems that may bve assoiciated  with both Hibiscus and Queen Palm. It is is called a nematode, most commonly a root know nematode In some parts of the country such as south Florida and the gulf coast states nematodes are a very common and major soil pest problem Traditionally in Arizona they have been associated with citrus and/or golf courses, but not as a generally common landscape pest. however, in recent
years they have been found on the roots of Queen Palms in Arizona and since they are found on Hibiscus in the aforementioned states I am assuming they may also be present in Arizona Most nematodes are microscopic, however one of the more common types that has been found on Queen Palms in Arizona is called root knot
nematode and microscopic leaves a telltale knot or nodule on the roots of infected plants The roots themselves are left stringy and dried up with numerous nodules present. They are very difficult to control chemically as most if not all homeowner accessible nematicides have been taken off the market due to their
very high levels of toxicity. You may want to contact the Maricopa Cooperative Extension Service or your local garden center to see if they might know of anything available. As with all plants keeping them in good health will help make them resistant, but not immune to pest problems. Both Queen Palms and Hibiscus
like soils that are well watered,well drained, high in organic matter and fertilized heavily on a regular basis with a dose of micronutrients, in particular iron, manganese and magnesium. Good luck. -- Plant Man

Q: This bush/tree is growing along the sidewalk on the east side of Hayden Library, near the MU.  They have had large seed pods but are now starting to bloom beautiful deep blue blossoms.  I could not read the 'sign' very well.  Some kind of bean.  Thank you. -- Dianne

A: I believe you are referring to the Texas Mountain Laurel (Sophora secundiflora). It is a plant native as its name implies to Texas and does very well in our area. The blooms are quite fragrant and there is also a less common white form available. One word of caution, especially around pets or small children the seeds/pods are quite toxic. -- Plant Man

Q:  Our first winter in SaddleBrooke we just let the plants do whatever they wanted. Since our 2nd summer, the lantana have spread too far and the oleanders have grown enough to no longer be an attractive shape (and I don't want them taller than 2-3 feet)...when and how far back can I prune both these plants?? -- Lynne

A: Both oleanders and lantana will respond well to what is sometimes referred to as a rejuvenation pruning.  In other words pruning the plant until it has only a few inches or so of top growth left. For these 2 plants this is best done beginning in the spring through the warmer months.  This removal of older overgrown tissue will  stimulated healthy new growth. If done during the winter the plants will survive, but may freeze back further if they encounter further really cold winter weather. -- Plant Man

Q: We moved into a house in Oro Valley that has oleander and Texas rangers with some cactus varieties.  There is a bush/tree in the backyard with profuse, thin dark green leaves and it blooms with yellow trumpet like flowers.  They don't really cluster though.  It doesn't have spines and it is VERY bushy and full.  I have no idea what this is and it needs to be trimmed badly.  Would you try to identify it and give me an idea what to do with it?  Also, I have two cactus in the front that look like very large aloe plants.  One has died and the other is dying, but not any of the other plants up there, including pear cactus.  What could be causing this problem? -- Beth

A: The plant with yellow trumpet-like flowers sounds as though it is probably Thevetia peruviana .  Although not a true Oleander it is commonly know as yellow or Florida Oleander.  Thevetia is best heavily pruned back during the warmer months.  Anytime beginning around mid- March through September would be best.  I would recommend from your description that a “rejuvenation pruning” would be in order.  A rejuvenation pruning is done on old overgrown plants that need a fresh start.  Basically this means that you can cut back the plant to within a short distance of the ground, say a foot or so.  Although this seems radical if it is done during the warmer season (Thevetia is a truly hot weather plant) in a few months or less it will grow back sufficiently to give a new healthy appearance to the plant. I am not certain what is causing the problems with the aloes unless it is simply old age.  However, normally even if the parent plant is dying back the new side shoots normally would continue to develop and spread. - The Plant Man

Q: I have 4 large Acacia over 6 ft high and would like to cut them back to 3ft to get them to a more manageable size. They are in bloom now and I would like to cut them back after blooming.Will this harm the bush or can I cut them back to the ground if I like,Also have some Oleander that needs pruning, is there anything special about how much you can remove? - Warren and Isabel

A: It sounds as though your Acacia may be a Sweet Acacia (Acacia smallii) or other similar species which may be grown as both a shrub and a small tree. If it is a Sweet Acacia itype it will normally produce a great many small sucker sprouts along the base and lower trunk areas. If you wish to do a rejuvenation pruning you may cut back to the ground after they are through flowering. From your description it sounds as though they are older shrubs and are in need of it. If you prefer not to do such a severe pruning they may also be "drop crotched' or pruned in a natural habit of growth by removing they long shoots as far back as possible and leaving the shorter ones intact.

If you have oleanders that are overgrown they may also be pruned either in a rejuvenation manner or in a naturalistic manner. I would recommend waitng on them until at least late March or early April when the warmer weather occurs as they are a true hot weather type of plant and will recover more quickly at that time of year.

Both Sweet Acacia and Oleander respond much better to either informal or rejuvenation pruning than to a formal type of shearing. I hope this answers your questions. - The Plant Man

Q: Our landscaper planted one brittlebush on the north side, receiving shade from the house, between the wash and the downspout. It is the only one that is stragley, drying up bottom leaves and has these tiny black bugs on the tips of the stems. I did hose the bugs off once but their back. I think the bush should be moved to a sunny and drier spot in the yard. Will this bush replant as it is about 2-3 ft high and was planted around Aug of last year? If it can be dug out and replanted should I cut it back first? If I should cut it back, how much should remain after cutting? or is it hopeless? Thank you. - Carol

A: Although Brittlebush is a perennial plant it has a top that dies back on a seasonal basis. Normally after flowering in the spring and early summer the silvery brittle leaves will gradually fall off and the plant should be cut back to stubs. This will greatly help to rejuvenate it. A sunny dry location is normally best. I would recommend cutting it back to within a couple of inches or so of the ground and digging out as much of the roots as possible and transplanting. Brittlebush does not always transplant the best, but if you do it at this time of year while it is dormant it will likely survive. again a dry sunny location with good drainage and either just drip irrigation or an occasional hand watering would be best. - The Plant Man


Q. Hello: We have four large date palms in our backyard and I need to learn how to take care of them; i.e., trim the branches that are close to the ground and get them to bear fruit.  What tips and/or suggestions can you give me? Thank you for your assistance. -- Deb

A. A very good publication that is available free on line from the University of Nevada Cooperative Extension Service (which contains input from the Arboretum at Arizona State University ) is Date Palm Gardening Guide For Southern Nevada by M.L. Robinson along with some other publications from the Nevada Extension Service on date and palm culture.  Their web site address is http://  -- The Plant Man

Q. Your web site is so pretty and helpful. I am interested in getting a Palo Brea (Cercidium praecox) . Is there one on campus I could look at? I couldn't find one under the categories listed on the website. Thank you -- Debby

A. We have a number of them on campus.  Some of the areas you may find them in include the parking lot south of the Agriculture building on the north side of Lemon Street , both sides of Orange Street from approximately the book store west to the Memorial Union, a number are also located in the Desert Arboretum Park .  Some of these trees will have labels identifying them as Parkinsonia or Cercidium praecox, commonly called Palo Brea or Sonoran Palo Verde. They can be distinguished from the other species of Palo Verdes by a very smooth yellow green bark, usually even on the trunk and older wood.  Hope this information is helpful to you.  If you need any additional please let us know. -- Plant Man

Q. Hoping you can tell me the name of the vine that is growing on the west side of the social sciences building.  It is currently bearing pink blossoms.  Kind of  heart shaped or arrow type leaves.  Would like to give it a try on my block fence.  Thanks. -- Diane

A. The vine in question is Queen’s Wreath (Antigonon leptopus) native to Mexico .  It is generally a good choice for the low desert, takes heat well, will usually have some die back with the cold, but soon will grow back again.  Another advantage is that it has no thorns. -- Plant Man

Q. We have a 25ft by 25 ft courtyard and need info for a tree in the midle. we looked at tipu and chinese elm. tipu has wide spreading roots so that may be a problem we trhink. and..if it's a chinese elm that's preferred..which one of the many varieties do u recommend? -- Al

A: A good source of information regarding various varieties of Chinese Elm (Ulmus Parvifolioa) is that of an on line publication from the University of Nevada Extension Service called Chinese or Lacebark Elm, publication number 85-33. Their web site address is:  One of the varieties contained in it called Drake is especially recommended. The only problem you may encounter is trying to find it locally.  I would suggest printing out a copy from the web site or making a list of the recommended varieties and take it to your local nursery.  They may also have other varieties they can recommend to you.  One of the biggest complaints regarding certain varieties/specimens of Chinese Elm is that some tend to be more deciduous than other or in other words are less likely to keep their foliage year round, especially in a really cold winter or in an extremely hot, dry summer.  Drake and some of the others mentioned in the above mentioned publication are reputed to be more “evergreen”.  Hope this information is useful to you.  Good luck. -- The Plant Man