GARDENING: Time to aerate lawns and restore mulches

It is a bit late to dethatch lawns now because there may not be enough time left this fall for the lawn to recover, but aeration would be OK. This would be a great time to renew any mulches that you need.

Any pruning you now do will leave the plants looking that way until next year. So prune with modesty unless you know what you are doing. Otherwise, any dramatic changes in plant shape or size should be delayed until just before new growth next spring. You could prune fruit trees anytime after the leaves drop. It's easier to see the plant form and how the branches are arranged with the leaves gone.

Fall's cold weather is here. If you haven't mulched plants for the winter, particularly those that are sensitive to freezing weather, you still have time. I would mulch the base of plants like bougainvillea, cape honeysuckle and African bird of paradise.

To do this, you could cut a 1-gallon plastic nursery container, removing the bottom and cutting up a side so that it can be opened.

Pull the container open and place it around the base of the plant, leaving a cone that you can fill with mulch. Fill the cone with mulch. Do not cut the plant back unless you see signs of damage. This will give the base of the plant some protection, provided the temperatures don't drop too low. If the tops dieback this winter due to cold, the mulched base should protect the base of the plant from freezing and the damaged plant will regrow rapidly from the protected base.

Watering cactus during the winter. I think there was a misunderstanding of what I was saying about watering cactus growing outside and in the ground. Cactus need to be watered during the winter months, but not as often as many of your other plants. You may be able to turn off your controller for cactus, but you will still have to handwater occasionally if you do. If you were watering once a week during the summer, you should be able to water once a month in the winter.

If you were watering once every two weeks, you should be able to water once every six to eight weeks. You won't hurt them if you water them more often than they require, provided there is good drainage. Cacti growing in containers need more frequent watering than those in the ground.

Question: What is your opinion on the use of anti-dessicant sprays on trees such as African sumacs, Bottle trees, and Phoenix Palms to keep them from freezing if we have a colder than usual winter in Las Vegas?

Answer: I found a couple of very weak references on the use of antidessicants, or antitranspirants, to prevent winter damage on plants. This has been suggested primarily in cold climates such as Indiana and Kansas, where the ground freezes and evergreens can't take up the water they need from the roots.

This happens usually above the snow line. The part of the plant above the snow is transpiring during the day when it is warm, but can't take up enough water from the frozen rootball to supply the top of the plant above the snow. The needles above the snow turn brown or dessicate.

In cases like this, they are suggesting that the use of antitranspirants will help the plant preserve water in the leaf tissue and prevent browning from dehydration. The problem is that antidessicants are fairly short-lived and must be applied frequently. They must be applied just before a damaging freeze, which is hard to predict.

In fact, I have a slide of winter dessication on pines just above the snow line from when I was in school in Minnesota. The snow melted and the top of a 6-foot pine had brown needles and the bottom of the tree, which had been below the snow, was green. I could find nothing to support the protection of plants from freezing by using antidessicants or antitranspirants.

Q: I took a cutting from a rose plant earlier this summer and have grown it into a healthy new plant. Now that the weather is getting cold, can I take it inside my solarium and treat it like a houseplant? Or does it need to hibernate?

A: I would resist the temptation to take it inside. Your instincts are correct. It needs the winter cold to "reset its internal clock" for the next year.

Plants that come from temperate climates with distinctive seasons use the changes in temperatures and the length of the nighttime to determine when it is OK to grow again for the next year. Interrupting this normal sequence of events by taking it inside will "confuse" the plant, and its growth may be affected the following year.

When we transfer our needs to plants and we begin to interpret what they need with our own needs, we begin to make mistakes in judgment about how to take care of plants. This is called "anthropomorphism."

The length of time that your rose bush needs to receive cold temperatures so that it "resets its clock" is determined by the number of hours below a threshold temperature, usually somewhere around 45 F. The number of hours below this temperature and the number of degrees below this temperature are called "chilling hours."

Chilling hours are calculated by adding up the hours of temperatures between 32-45F and subtracting the number of hours over 65. Chilling hours influence bud break, flower set and the quality of new growth.

I would leave it outside for the winter. You can bring it inside in about January and force new growth early if you want, but it will require six to eight hours of full sunlight each day or the growth will be weak and spindly.

The other problem you will have is taking it outside. The growth it will put on in the interior will be very different than when growing outside. Putting a plant outside, when it has been growing inside, will shock the plant until it can get readjusted to the higher light intensity, wind, lower humidity and other factors. This will require new growth under the outside environment.

Q: Can I take a new plant that I started from a cutting just this summer and transplant it outside, or is it too soon? Can I just plant the container in the ground instead?

A: If you are going to take it out of the container, I am concerned that the rootball will fall apart. It might not be established well enough to hold the soil around the roots. If it does fall apart, you run the risk of it not making it.

But if you are careful and you transplant it into a waiting hole and cover the roots quickly, it will probably be all right. The transplant success will be due to keeping the soils from breaking too much and keeping the roots wet. If the rootball falls apart, you have to be very quick to get the roots into the soil and covered. If the rootball remains intact, then your success will be much higher.

The only way I would plant it in the container would be if you double potted it -- planted it into a larger container with mulch. But you are better off getting it into the ground if you can. Be sure to mulch it and water it more often than established plants, but also make sure the soil drains or the roots will rot. Planting too late in the winter can require a tricky balance between too much and too little water.

Q: Can you tell me when is the best time of year to plant conifers?

A: You have two opportunities to plant conifers such as pines at the right time of year. The absolute best time is when temperatures are cooling down just prior to winter.

Depending on your climate, this might be any time from September to October. In the desert Southwest, this would normally be October. Soil temperatures should be warm enough to encourage root growth (50-65F) but not too cold so that root growth slows or stops (usually 45F).

The second best time is spring during this same window. However, these plants can be planted anytime if they are in appropriate containers or the rootball is protected.

Bob Morris is a horticulture specialist with the University of Nevada Cooperative Extension.


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