Xtremehorticulture

Xtremehorticulture of the Desert

Bitter Orange a Good Choice for Las Vegas But….

Leave a Comment / bitter orange temperature, citrus, cold damage, las vegas landscape /

Q. Is it possible to grow sour or bitter orange in Vegas? It’s becoming almost impossible to find at the local markets and we use it in so many recipes. I was curious if that was something that might grow here? When should I plant it? Bitter orange, sometimes called trifoliate orange, is a good choice for colder climates like Las Vegas where it oftentimes freezes. A. They aren’t very popular here. I understand why you might want to grow them. We are talking about Citrus aurentium. They are used as a landscape highway plant or landscape hedge in the Phoenix area where it’s warmer during the winter. Here they are mostly used as a low temperature rootstock for citrus when shipped to our area by wholesale nurseries. Trifoliate orange is used primarily as a freeze tolerant rootstock for our area, but sour orange is also used. Sour orange is used as a rootstock for citrus needing to be cold hardy. If the top of a citrus dies due to freezing temperatures, at least the rootstock will sprout and grow after the top freezes. I don’t have the information on their low temperature tolerance for the winter, but I think it’s around 20° F so it would be a good choice for planting in the Las Vegas area. Meyer lemon and kumquat, two more commonly grown citrus here, will handle freezing temperatures to about 24-25° F. once established. In protected backyards Meyer lemon, grapefruit, and kumquat survive most of our winters. So, my guess a fifteen-foot sour orange will be at least reach those temperatures, if not a bit lower. This tree should start flowering in about year four to six. You will still lose fruit due to early spring freezes combined with open flowers in some landscapes depending on its exposure to early spring freezes and wind. But the tree itself should survive our annual fluctuating freezing temperatures for about 25 years or more. Remember ALL citrus are from China and parts of southeast Asia. This means the desert soil needs to be amended at the time of planting, and periodically adding amendments to the soil. No citrus are xeric so they will need about the same amount of water as regular fruit trees of a similar size, about 4 to five feet of water under applied under its canopy in one year. Just for your information bitter orange does get a deadly disease occasionally but it’s usually not prevalent in non-orchard citrus areas so you should be all right. Buy the tree smaller and protect the tree from sun damage through shading itself or providing it shade while it gets established. Buy a tree that is shrublike. You won’t find it locally. It is not that popular as a tree on its own. I think you will have to order it online. Places outside of the desert southwest don’t have to worry much about sun damage to the trunk so it is limbed up higher into a tree. For this reason, you want to buy it grown into as much of a bush as possible. Limb it up later when it gets older and acclimated to our desert. The best places to order it are from Arizona nurseries such as Whitfill or Greenfield if they will ship it to you. Both are in the Phoenix area. Plant it when temperatures are cool, but spring planting is best in the case of citrus. Because of digging and availability, most nurseries sell bareroot trees in the spring. Bareroot trees need to be planted as early in the spring as possible. Potted or container trees can be bought anytime but planting them is always best in the spring. If it were totally freeze tolerant, or you were sure it will not get extremely cold this winter and you can find it available, then fall planting is always best.

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Why Not Encourage Winter Planting in the Warm Desert?

Leave a Comment / cold damage, freeze damage, when to plant, winter /

Q. Why do you encourage people to avoid planting during the winter months? I can understand it in Minnesota but why southern Nevada? Oleander winter freeze damage during a particularly cold winter. A. Simply because I don’t know what is going to happen. I tell you spring and fall are the best times to plant. If it is a warm winter. then planting during the winter is okay. But if it is a cold winter, such as the lower teens at night, then be careful! Plants need soil at least at 45 -50F to grow roots. Otherwise the roots just sit there until the soil warms.  Winter Freeze? Cold or freeze damage to myoporum (locally known as Australian racer). Will it freeze this winter or not? If the plant is winter tender, like bougainvillea or most citrus, then you are playing Russian roulette with the winter temperatures. It is best to plant those (that might freeze during the winter) in the spring for that reason. Winter freeze damage to bougainvillea.

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Grape Vine Killed by Winter Cold

Leave a Comment / cold damage, grapevine dead, Winter freeze /

Q. I planted two vines in my backyard  3 year ago and it sprouted and grew very quickly but as you can see this year it has not done anything with the exception of the few countable leaves and the three new shoots.  I do notice some holes in the few leaves.  I live in Montreal Canada.   A. You are a little bit out of my climate zone but I’m going to take a stab at it. I am guessing, from the looks of it, it had some winter cold damage. There is a difference in cold tolerance among grapes. Those with some vinifera genetics in them (most of the European wine grapes are vinifera types) are less cold hardy than some of the American hybrids. For instance Thompson seedless grape has vinifera in it and is less cold hardy than Concord, an American grape. I don’t know where you got your particular grape and whether it was grafted onto a rootstock or not but if it was grown on its own roots than any suckers which could grow from it could be used to replace the dead vine. Suckers growing from it should be extremely vigorous because of the already larger root system. It could be back up on top easily this growing season if you remove all but the strongest sucker. As it grows longer, tie it to the post. Strip all of the leaves and shoots off of this sucker until it finally gets on top. This way it will grow faster and you will direct the growth. Give it a little extra water and nitrogen fertilizer and it will grow faster when the temperatures are warm. That’s my best guess at it given the information I have and pictures. I saw one strong shoot coming from close to the ground in one of your pictures. You would cut it just above the strongest growth to reestablish it.

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Protect Citrus From Freezing Temperatures Soon

Leave a Comment / citrus, cold damage, orange, winter freezing /

Q. When should I begin to protect plants like citrus from the freezing weather that’s coming? A. Some citrus will handle the cold weather better than others. Most of the citrus sold in this area are grafted to a cold hardy root system called a rootstock. Damage or even death results when the temperatures remain low enough to kill the top of the tree, its root system or both. This citrus died from winter freezing temperatures several years ago and the sour orange rootstock grew in its place producing oranges that were too sour to eat.             The more cold hardy and reliable citrus here are kumquat, grapefruit and Myers lemon. However, they will not survive the cold if the roots which they are grafted to are not cold tolerant as well. Most plants sold by nurseries in this area have citrus on cold hardy rootstock. This might not be the case if you buy citrus online. Spring freezing weather caused this fig to die back and push new growth from lateral buds along the stem.             None of the citrus are severely damaged if temperatures remain above 32° F. The least cold tolerant of the citrus, such as limes, is damaged when temperatures drop below freezing. When temperatures are low enough to damage the top of the tree but not the rootstock, suckers or water sprouts grow from the rootstock the following spring while the top of the tree may be dead or severely damaged. Freeze damage to bougainvillea             As we start getting close to 32F, start watching the local weather reports or track the low temperatures online. When you see projected temperatures reaching 32° F or lower, wrap the base of the tree with a blanket or cover this area with mulch. Smaller trees or trees pruned into an espalier may be entirely covered with a blanket.             Some people wrap tender trees with Christmas lights on a timer that comes on at night. This may work if temperatures are not extremely low and there is no wind. Blankets should be removed the next day when temperatures climb above freezing.

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When to Cover Winter Tender Plants in the Mojave Desert

Leave a Comment / cold damage, freezing damage, winter protection /

Q. When should we cover Pygmy Palm, Bougainvillea and other plants that will freeze here in Henderson?  I have burlap to cover them. Bougainvillea freeze damage A. Both of these plants can tolerate temperatures to near freezing and they don’t seem to have problems at temperatures below 45° F that causes chilling damage to some plants. Some tropical plants such as tomatoes may show chilling damage to fruit at temperatures below 45° F. This is why it is best to not refrigerate tomato fruits.             It seldom freezes in the Las Vegas Valley before Thanksgiving. After Thanksgiving you might expect freezing temperatures at the higher elevations such as in Summerlin or in very low spots in the Valley where cold air collects. In Henderson, this might be in the old Pittman area or along the wash.             Cold air, being heavier than warm air, settles into low geographic areas. Cold air tends not to settle on gently sloping land or hills.             Freezing temperatures are more frequent where plants are exposed to wind. Plants growing along major streets tend to freeze more often than those in protected backyards. Major streets are urban canyons that channel cold wind in the winter. Backyards are more nestled away from these exposed urban canyons. Sehgal palm cold damage             Plants growing close to brick or cement walls that face West or South are less likely to freeze than plants growing further away unless wind is involved. Brick and cement walls exposed to the sun store heat during the day and radiate this heat at night keeping the plants a few degrees warmer. If wind is involved, it removes this radiant warmth making these plants more susceptible to freezing temperatures.             Bottom line, when the weather forecast is for freezing temperatures, cover the plants with an old sheet, blanket, or in your case burlap, before nightfall. Drape this covering over the soil or any surface that can radiate heat at night. Remove this covering the next morning after temperatures are above freezing.             In open areas, expect freezing temperatures after Thanksgiving and up to March 1. In protected areas, expect these temperatures anytime between mid-December and mid-February but watch your local weather forecast closely and adapt this recommendation accordingly.

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Assess Plant Cold Damage in the Spring and Fix It

Leave a Comment / cold damage, cold protection, frost damage, Frost protection, how do I protect plants from cold /

Q. Are there are any plants I need to prune or trim down before the frost comes to the Las Vegas valley this year?  I noticed that oleander suffers greatly from frost, foxglove, asparagus ferns, potato vine and a purple flower trumpet flowered plant are kissed when the frost comes. Should these be covered also? A. Damage from frost will be variable in different places throughout the Valley. There are places which are naturally cold spots and others in windy locations. These areas will be hit the hardest.             Then we have the variability of the weather. It was not too long ago that we had unusually Difference in cold damage between two different types of Oleander warm winters where it hardly froze at all. Then we had a terribly brutal winter with the coldest temperatures hitting us in February when plants were just waking up from dormancy.             Then we have variability in the plants themselves. As far as oleanders go, there are winter tender types and there are very cold tolerant types.             My basic advice is to leave most ornamental plants alone. Wait until the coldest part of the winter has passed, or you begin to see the beginnings of new growth, and then remove what has been damaged. Oleander and asparagus fern can be pruned to within a few inches of the ground and they will recover. Oleander will recover by summer if it is pruned to within a few inches of the ground. in late winter             This doesn’t hold true with citrus. Citrus planted in cold locations will have to be protected if you want it to survive or you want fruit.

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Bamboo Can Be Cut Back to Repair Winter Damage

Leave a Comment / brown leaves, cold damage, freezing damage, iron, repair bamboo, yellowing /

Q. I have bamboo that was damaged last winter as you can see from my pictures. New growth is emerging from them but they are still yellow and brown. Should I fertilize them or give them iron? A. If the plant is still brown from winter damage and the growth is yellow, the only way to really make them look good again is to cut them down and let them regrow from the base. This kind of damage is never going to recover from unsightliness without some regrowth.             I assume this is a running bamboo like golden bamboo. They should come back if they are cut back to the ground but this is not the ideal time to do it. Prune cautiously this time of year.              It would be okay to cut back the largest ones now but leave younger ones until you saw some good solid growth again from the base. Once you see healthy growth, go ahead and cut more back. Otherwise wait until next spring which would be ideal.             Fertilizer and iron will be helpful as it is growing back.

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Lantana and Yellow Bells Should Not Be Dead from Winter Cold

Leave a Comment / cold damage, desert, freezing damage, lantana camara, Las Vegas, Tecoma stans /

Q. I have had Tecoma stans, Yellow bells, in the backyard as well as lantana for the past 3 or 4 summers. They do well but never winter over. When I dig them up to replant, the root structures seem to be healthy and alive. The tag on the plant says they are cold hardy. Is there anything I can do to help them winter over?  What is Yellow Bells? Picture of Yellow Bells from Arizona State University website What is lantana?  A. Are you thinking they are dead because the tops die back? It is seldom that I see these plants totally die out in the winter here. They do frequently die back to within a few inches of the soil surface during the winter.             They then can be cut back to about one inch from the ground in February and they come back like gangbusters in early spring with some water and fertilizer. Lantana cut back in the winter to about two inches in a rock mulch in Las Vegas.             If they are dead, I am wondering if they are not getting enough water during the winter months to keep the roots from dying out. Normally a watering schedule of about every ten days or so would be enough during the winter to keep them alive.             Otherwise try mulching over the tops of the plants with a few inches of wood mulch to keep the winter cold from damaging the roots. It is very rare these would die out in the winter here under normal landscape situations.

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Repairing Lemon Trees From Winter Cold Damage

Leave a Comment / citrus, cold damage, desert, freeze damage, Las Vegas, Meyer lemon, Mohave Desert, Mojave Desert, nevada /

Q. Our lemon tree shows damage after our recent very cold spell.  Some of the leaves are dry and dropping.  Is there anything we can do to assist the tree? A. The damage can take several different stages. The degree of damage depends on the lowest temperature reached, the amount of time at this temperature and the source and condition of the plant.             The first stage is slightly below its tolerant range and results in leaf damage and other soft tissue death while the stems remain relatively undamaged.             The second stage is at temperatures slightly lower or held for a longer period of time. This results in leaf damage or leaf drop and death of smaller stems.             The third stage is complete death of the limbs and trunk back to the rootstock. The rootstock is normally a very hardy citrus grafted on to the more tender citrus.             In this third stage the more valued lemon portion of the tree completely dies but leaves behind the more cold-tolerant rootstock. When temperatures warm, the rootstock will sucker into a totally new, but different, citrus tree.             You can get some idea now by bending some branches and see if they are supple and bend or if they snap off. But you will not really know the extent of the damage until you see new growth in a month or so.             Once you see where the new growth is coming from you can make a decision to keep the tree or remove it and start all over. If you have suckering from the limbs then you might want to prune it back and let it regrow.             If suckers just come from the roots then it would be wise to remove it.

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Sago Palms Damaged in December

Leave a Comment / cold damage, freezing damage, sago palm /

Q. Do white fronds indicate my sago palm has frost damage? Can my sago be saved? Should sagos be wrapped and, if so, do I just cover them when the temperatures drop down to the 20’s but then remove the wraps once the weather warms up? A. Judging from your picture, yes, it appears to be frost damage. Not to worry. The brown fronds are permanently damaged. As long as the central crown is alive (you will know in the spring when you see new growth) then leave it.  I am guessing that it was just warm enough near the rock surface to provide heat to keep the bottom fronds from damage. The center was protected by the fronds around it. The central fronds probably got some cold and wind damage combined.             As the central fronds become older, expand and become more horizontal they will grow above the damaged area. The damaged fronds can be removed by cutting its support as close to the trunk as possible. I would not do this until you see the newer fronds coming in and getting established. Cold damage to sago palm in a previous year from another reader             Of course this leaves the older fronds at the bottom still green. If this looks too funny to you, remove them too after you see solid new growth from the center.             Normally we don’t wrap sagos. You can, but we normally don’t. It looks like yours might be in a tough spot for cold wind and this got those fronds, probably the December 5 and 6 extended cold we had. That extended cold is unusual for us. Maybe every 5 to 10 years.             The timing of the cold, the length of time below freezing combined with some cold winds probably did it. Those are hard to predict. The choices I would say might include moving it to a more protected location, living with that kind of damage every few years, wrapping it, using some plant paint to cover the damaged parts or prune them out.  If you cover it then yes, cover it when temperatures are threatening and remove the cover the next day.

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