All Your Winter Gardening Questions Answered
The winter solstice has passed but we’re still in the middle of winter here in the valley.
That is if you can call 60-degree weather a real winter. So how are all those plants and gardens doing in this mild weather?
Norm Schilling and Angela O'Callaghan, co-hosts of KNPR's “Desert Bloom,” answered those gardening questions.
On the mild winter and hot summer:
Norm: When I first got into gardening here, 30 years ago, the average first frost date was November 11 and the last was February 11. To date, here in January, I've noticed two days that the temperatures dropped to about 31. That is exceptionally warm.
Angela: If you look at data from NOAA - the National Oceanic and Atmospheric Administration - they've been saying that this winter thus far has been several degrees higher than the norm.
We've had higher temperatures for day and night time. When you think about plant stress, nighttime heat is worse than daytime heat.
Norm: which is not a problem right now, but in the summer.
Joe: Why is that more stressful?
Angela: When it's hot, plants when there is sunlight they produce sugar, which is whatever thing else gets built with. When you have heat, more of that sugar is broken down without doing anything beneficial for the plant. It's just broke down like sweating - almost. When the plant is hot at night, it is breaking down that sugar but it is not replacing it as it could during the day. It doesn't get its rest period. The warmer it is the worse it is.
Norm: These plants are getting breaks. It has really caused me to think what we're doing here and what have been doing here in terms of plant selection. Plants that were dependable 10 or 20 years ago are struggling and succumbing to disease. Like ash trees... purple leaf plums, fruit trees. It's these moderate-water-use plants that come from temperate climates. They've always been challenged by our soils but now that heat load, their ability to take up enough water to do all the work they need to do to keep them as healthy physically it is just being over-challenged by the huge heat load.
On the warmer temperatures and pests:
Angela: When nights get chilly, that tends to cut down on the activity of the insect pests we deal with. Also the cooler it is, the less likely that we're going to have a huge fungus population.
Since most plant diseases are caused by fungi and we usually don't have that problem because we have such low humidity but now that plants are being stressed by high temperatures along all the other problems they have to deal with here like poor soils, now they don't have the resources to fight pests.
I'm thinking of things like aphids, which are impossible to avoid, but now nothing is going to cut down on that population. There are lot of insects pests that we would like to keep to a dull roar, but when we have plants that can fight back we'll see more pests.
Caller Mike from Ely wanted to know what kind of shrubs will attract birds and will pyracantha grow in the area:
Angela: They can certainly tolerate our heat, so why would they tolerate the cold. I would certainly give them a shot because the berries are certainly something the birds will go for.
I personally say plant a fruit tree and it will attract every bird in the neighborhood. A lot of fruiting shrubs will do fine.
Norm: There is a type of grape that is rogers red, that is not edible to us, but birds love it. And it gives a very nice fall color show as well.
Rogers red grape/Flickr/John Rush
Caller Skeeter from Overton wants to know when to transplant a leafy plant from a pot to soil:
Norm: After the heat. Whenever you planting or transplanting and you're disrupting the root system, you want to give that plant has much time to develop a root system, which it is going to do through the cool season even when its cold outside our soils don't freeze. They can have more of a chance to develop that root system before it gets hit by the heat.
Fall is the best, but you still have time now.
Is it warm enough to plant tomatoes:
Angela: Probably you want to wait a little bit. Certainly, you're not going to want to start them outdoors. You always start your tomatoes indoors because they have such a crazy temperature requirement even though they're warm season. You don't want to run the risk of having cold nights that go below 40 degrees, which will make them very angry.
Wait until February, if we continue to have nights like we've had here, you can definitely put them in by February.
Caller Rob from Boulder City wants to plant citrus trees:
Norm: You should be fine planting now. If it gets cold enough long enough, they can take damage but they can take temperatures when they drop below freezing for a little bit.
When you do the planting, over dig the hole in width, not in depth and bring in a little organic matter, soil sulfur, bone meal, and good slow release organic fertilizer with micronutrients - a nice starting fertlizer - mix that up into the native soil and use that as back fill.
On Facebook Jacqui Bird asked: I have several fruitless mulberry trees that still haven’t lost all their leaves and over the past year have had one die. I’ve since learned they are approaching the end of their life cycle (+45 years old) and had attributed the loss to that, but now with reports that the valley hasn’t reached below 32’ in 2017 and this past seasons’ leaves refusing to fall, I’m wondering if my trees are not getting enough dormant hours per year and if that could hasten their demise.
Is this a thing? Can you suggest some life support for the old ladies in my backyard?
Norm: The 'old ladies' in your backyard are probably men because mulberry has male and female trees.
I don't know if there is anything you can do in terms of keeping them healthier with the change in climate. Don't trim them much. Just take out the dead wood. Keep them fairly moist. Give them a good deep soak. And fertilize them in the spring and the fall.
Angela: And if they haven't lost their leaves don't try to make them. They will drop some. They'll go on their own schedule as long as you're doing the best horticultural practices you can: making sure it's watered, make sure it's fertilized, making sure there is nothing horrible eating the roots.
What is a 'bee garden?' and should we be planting them?
Angela: Anything with flowering plants is a bee garden.
Norm: Yes, we should be doing anything we can to support natural ecosystems in our urban environment.
The main thing is to eliminate or minimize the use of pesticides, especially system pesticides, which are pesticides that are applied in the soil and the plant takes it up. And whatever feeds off it - either through fruit or flower - takes in the pesticides.
Neonicotinoids are strongly suspected in bee decline.
Angela: One of the things we find a lot when we really cut back on our use of pesticides is we start to encourage natural enemies.
Caller Gina would like some ideas for shrubs that don't look like 'a pile of sticks' after a few years like the ornamental rosemary and texas ranger sagebrush looks like.
Norm: Dwarf oleander, dwarf bottle brush, tecomas will do well.
Angela: If the shrubs - ornamental rosemary and texas ranger - were cut into flat tops or balls - heavily pruned - that also causes them to look like a bunch of sticks.
Norm: With there is a down period and you can prune them pretty hard and the time to do that is now and in February. You cut them back pretty hard and in the spring, the flush back out. They grow back. Then you try to persuade your landscaper not to cut them back into balls and boxes. Then once every few years, when they start to get too big, you cut them back hard again. They're attractive plants when they're pruned properly, which is not hedge sheering them into balls and boxes.
Texas ranger sage/Wikicommons
Kurt from Henderson started asparagus from seeds and wants to know how long he'll have to wait for the vegetable to be mature:
Angela: Asparagus is a great choice for southern Nevada. They don't mind our salty soils, they're drought tolerant, they're high ph tolerant, and they can tolerate our boron.
It is going to take two years, maybe three - especially since you started them from seed.
Once you start seeing them producing it will be two years, maybe three and you'll start seeing those half-inch spears, and you'll have the plant for 20 years.
Willobee from Reno wants to know about ways to deter rabbits and squirrels:
Angela: Some of them not crazy about garlic. So grow garlic around things. You can also buy coyote urine and spray that around.
Norm: There are different products that claim to deter rabbits and other garden pests. Buy a little bit of those products and see which one works. But the other idea is to plant 'rabbit resistant plants,' like garlic, which is an ornamental plant that looks quite nice and is cold hardy so it should do fine [in the Reno area.]
Angela: The other thing we do at the cooperative extension after we plant edible plants that squirrels and rabbits love is we put down a layer of very, very light row cover, floating row cover, which light polyester. The bunnies don't see the plants underneath.
Row cover/Flickr/Aaron Baugher
Caller Lois from Las Vegas has two questions. First, when is a good time to transplant cacti and when should she prune roses?
Norm: Traditionally, the time to prune back roses is today. It's this month or maybe into February. Strip off the old leaves. Prune them back during the dormant season.
As far as transplanting cacti, cacti are succulents. You do want to wait for warmer weather, March, latter part of March and into April.
Kristen from California wants to know if she can grow the desert wildflower - desert five spots - in her garden:
Angela: I've only seen them wild. I would start with Jepson Desert Manual it will have some good information on starting desert plants because you don't want to put them in pure sand and you don't want to put them in anything too rich because they are desert plants.
Caller Jessie has some orange and lemon trees that have yellow leaves:
Norm: Use organic mulch. Put down wood chips all around. That's going to help long term. You need to find a fertilizer with a good micronutrient mix, in particular, manganese, zinc, iron, and magnesium, which you can also get through Epsom salts.
Angela: When you start seeing overall, yellow leaves you might start thinking about putting down some high nitrogen fertilizer as well.
From Nevada Public Radio: Desert Bloom
Norm Schilling, horticulturist, Schilling Horticulture; Angela O'Callaghan, associate professor, Nevada Cooperative Extension, specialist in social horticulture