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Navigating Winter Gardening In Las Vegas

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The winter weather picked back up in Las Vegas this week. Is your garden ready?

It’s the first day of February. Nights are still a bit chilly – generally in the 40s.  Days are getting up there into the 60s.

It might be the right weather for Maple Sugaring in Vermont – but does this change in temperature, over the course of a day, present special challenges for the desert gardener?  Or maybe there’s some advantage to cold nights and warmer days.

On aloe vera surviving cold weather damage:

Norm Schilling: It depends on the species, but in most cases just wait a little bit and it should recover. A lot of aloes are really cold sensitive you can't grow them here. But things like aloe vera probably somewhere around 25 degrees it will start taking damage and typically what will start happening is the young tissue, the outer tips of the leaves, will see damage first. All you need to do is wait a little while, it will continue to grow and  when it naturally matures those pieces will separate and you break those pieces off.

Do the warmer days and chilly nights of late winter and early spring present special problems?

Angela O'Callaghan: It depends on how adapted the plant is to start... If it's a perennial plant, meaning it comes back year after year,  as long as it's got a good strong established root system, you would be amazed at what it could tolerate.

Support comes from

Do the microclimates of the valley impact how plants grow?

Norm: The east side of the valley is the warmest both in summer and winter by maybe three to five degrees. The center of town is generally just a little bit warmer. It's the perimeter, the far south, the far west and far north parts of the valley that get the chilliest. So those areas are a little bit more challenged. 

What can you do about weeds in your yard?

Norm: You can use chemical controls to kill existing plants. So that's a post emergent herbicide, in other words, after the plant emerges you spray it after it comes up. There's pre-emerge herbicides which is a chemical you put down. It's granular. You water it in. It keeps weeds from coming up, but I do believe the best approach is to just pull the weeds.

"The one thing you've got to do is get the weeds out before they go to seed. A lot of these weedy plants have really short cycles. So a few weeks, a couple months after they germinate, they'll be putting out there seed"

Angela: Trying to weed in rock mulch is kind of a challenge, but what I've discovered is I have one of those steam cleaners that you use clean the groat in my kitchen. Well, I take that long nozzle and I push it through the rock and zap those weeds. What happens is it boils the sap in the plant

Caller KC asked: When is a good time to plant artichokes from seeds?

Angela: Since you're starting them from seed not transplanted this would be a good time to get them started because they're cool season plants. You want to get them started indoors. Don't put them in the ground outdoors. Wait until they get a little bit of what we call true leaves, they look sort of like a thistle, then you can transplant them. You probably won't get much in terms of production this year, but next year, because they are perennials.

 

Caller Kristen: What can she use to eliminate bugs that are piercing the skins of pomegranates?

Courtesy: University of California Cooperative Extension

Norm: The insect you are probably referring to is the leaf-foot bug. You can identify because their back legs have what looks like a leaf on the back of it. They're piercing, sucking insects. They can do a lot of damage especially to pomegranates. What I found works really, really well is diatomaceous earth. What you do is find bellows... put some in there and get food grade diatomaceous earth and just spray it on them and it just messes them up fast and hard and it's completely organic.

Angela: Also, there is a thing called surround wettable powder and it's a very finely milled clay. What we found because we've had some horrific infestations. We have a pomegranate demonstration garden at the Cooperative Extension office... What we've found with this surround wettable powder, you shake it up into a suspension, literally pour it on. And what happens is it confuses the leaf-footed bugs. They don't recognize that this is something they like. So they stay off. 

Caller Clay: A weed that kind of looks like corn is growing in his backyard is taking over? 

"Johnson Grass (3215391960)" by John Tann from Sydney, Australia - Johnson Grass. Licensed under CC BY 2.0 via Wikimedia Commons - 

Angela: What it sounds like he's describing is Johnson grass. That grows tall and produces rhizome, pretty sure that's what you were calling tubers, its a noxious, invasive terrible thing. And it's a perennial and the problem that or any weed that produces rhizome, or stolons or tubers is that if you pull the plant up and you don't get all the rhizomes then what you've done is said, 'oh, well now all the babies are going to emerge." The thing to do is when you pull it make sure you get all the little offsets.

Norm: or option 'B'... if you have underground runners, it's like Bermuda grass. The only effective way I know to kill off Bermuda grass is to us glyphosate which is the active ingredient in Roundup. Many people are anti-Roundup and for good reason I believe. So I don't want to use it unless I really have to. 

Is it time to start planting tomatoes?

Angela: What you should do is start thinking about what varieties of tomatoes that they want and you can start them indoors, because you do have to start them indoors, if you are starting from seeds. If you're going to be growing tomatoes look for tomatoes that have the shortest day. Like you'll see a lot of them that say it takes 80 or 90s before you get a full-sized ripe tomato, you don't want that. What you want is something that takes fewer days to become ripe because by the time the fruit is ripe... it's hot. It's dry and what you get is something that looks like it has been poached on the vine. So, you want to do is get your seeds going indoors now and get them in the ground by the third of March. Make sure they're protected from any sudden chill and you should be okay."

Caller Ed: What should I do to make sure my crepe myrtle has dense blooms?

Norm: Crepe myrtles bloom on new wood. So to get them to bloom more prolifically you should prone them fairly hard. In particular, take off all of the spent blooms. You should pay attention to where you're making the cuts don't just whack at the thing.

Crepe myrtles like a lot of water and they don't like our soils that much. So, work a little compost into the soil and then put organic wood chip mulch all around the base of the plant and even extend beyond the base and make sure you have more than one or two emitters right at the base of the plant.

Caller Amy: What fruit trees work here and when can you plant them?

Angela: Now is a great time to plant fruit trees. Make sure that if you're planting bare root that you're planting them so that decent but not overly rich soil... What we've found here is all those stone fruits peaches, apricots, plums, nectarines, they are so wonderful here. They just do terrifically well and the fruit I think is the best in the world. 

Caller Skeeter: How do I get rid of the green caterpillars that invade tomato plants?

"Tobacco hornworm 1" by Dave Pape - Own work. Licensed under Public Domain via Wikimedia Commons - 

Angela: Those are tobacco hornworms... They way to get rid of them really is to pick 'em off. You can use systemic insecticides but then you wouldn't want them on your food. What you can do is the diatomaceous earth will work. I put BT on. It's a bacterial product and the bacteria produces a toxin that kills the caterpillars. 

How do you properly trim an olive tree?

Norm: The rule of thumb is that you shouldn't remove a quarter of the total foliage in a year on a tree. If you do, you stress the tree out. It is all of its energy production all of those leaves. Olives are very drought tolerate so all you can do to reduce the amount of water up to a point will slow down its growth. And by the way, this is true of all desert trees: palo verdes, mesquites, African sumacs, acacia, once they are established you can probably water them four, five or six times a year. Give them a good deep soak and they'll grow slower and that wood would be stronger.

Caller Joe: What should I do about overgrown shrubs?

Norm: I think the biggest teaching point I've made over the past five or 10 years is this: the key to successful gardening is to put a plant where it wants to be, give it room to grow and then drink some wine. By doing that, your plants are happy and healthy. You don't have to cut them back. A lot of the work we do in landscape is because eight foot plants are in three foot space. 

Caller David: Do iceberg roses do well in Las Vegas?

Courtesy: Pixabay

Angela: Roses are so hardy... They are like troopers. I have an iceberg rose at home, brilliant pink and it's just has happy has a pig in slop. Very little work. They are happy.

Norm: Roses do very well here. It's not a desert plant. So when ever you're planting a non-desert plant. I really, really want you to put organic mulch, wood chip mulch around the base of the plant and beyond. It makes a really big difference. 

We have fewer problems growing roses than people in more traditional gardening climates where they have to deal with some nasty fungal disease and stuff that we don't deal with because of the dry climate.

What about pruning roses? In the winter time should you strip off the leaves and cut them back?

Norm: It's a good thing to do. You actually want to force the rose into dormancy. And you're going to get a better blooming season. The following year. 

RESOURCES: 

University of Nevada Cooperative Extension

Master Gardeners

Mountain States Wholesale Nursery

High Country Gardens

International Society of Arboriculture

From Desert Bloom: Winter Planting 

Desert Bloom
Jan 29, 2016

Winter Weeds

Guests

Angela O'Callaghan,  Associate Professor at UNLV’s Cooperative Extension program; Norm Schilling, owner of Schilling Horticulture in Las Vegas.

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