Keeping soil moist is important in fall weather

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Question: When is the best time to water a new landscape and how many times a day should new plants and trees be watered now that we are going into the fall weather?

Answer: If the watering is done by drip irrigation it won't really matter, as long as the soil surrounding the roots is going into the heat of the day with enough moisture. With a new landscape we are trying to establish the root system into the landscape so any type of stress will limit the plant's rapid establishment.

It also is important to not have the soil kept too wet or the plant will be stressed as well. So when establishing plants you must have good drainage and then water when the soil begins to dry. Determining when to irrigate is more of an art than a science.

It will be critical to get your plants established to make sure they are mulched with 3 to 4 inches of wood mulch on top of the wetted soils. With a mulch you should be able to go at least two days between waterings with temperatures are still near 100F. You will have to water once a day if you do not mulch and the plants will be stressed.

Plants in containers are a different matter. I have mentioned in the past that the time to water plants in containers is in the early mornings. This information may be getting confused and transferred to plants in the ground.

Generally, most plants will need to be watered in containers a minimum of once a day in summer months. In this case, watering in containers should be done just before the day gets hot so the container soil will not overheat. Dry soils in containers can reach temperatures of 150F or more on the sides toward the sun. This will kill half of the root system.

Most plant roots can't take temperatures more than about 115 to 120F. Moist soils will warm slower than dry soils. Soils in the ground do not heat up as much as container soils and so the time of day is not as critical.

Q: I installed a wide variety of plants including desert and nondesert plants. I need information on how much to water at different times of year, what type of fertilizer to use and when, and the best time is for pruning. I don't mind doing the research myself, but I don't know where to go for the information.

A: Lets get some guidelines going for landscaping in general and some exceptions.

First of all, there are exceptions and alterations in the following:

Fertilizing. You will nearly never go wrong fertilizing during December and January on most anything in the landscape. This is your default time for applying fertilizers. Most woody plants will require just one application. This is also the best time to apply iron fertilizers.

For the most part you will never go wrong using a fertilizer high in nitrogen for nearly all plants where you want to get lots of green growth; leaves, stems and such. An example of a good fertilizer that you can use on lawns, trees and shrubs would be something like a 21-7-14 or 20-5-10.

There is nothing wrong with tree or shrub fertilizer stakes. Organic fertilizers such as those from manures are always a better choice than mineral fertilizers. Manures can be animal manures or plant manures. Compost is one example of plant manure.

Flower and fruit production require phosphorus. A fertilizer high in phosphorus would be a wise choice. Phosphorus encourages flower production. Find a fertilizer with no zeros for numbers on the bag but with the highest value in the middle number (phosphorus).

Plants that flower may require multiple applications of fertilizer during the year particularly just after flowering. If plants are not looking their best, try giving them a small amount of fertilizer. Many desert types of plants require less fertilizer than nondesert types but you can use the same kind.

If you have drip irrigation, apply the fertilizers around the drip emitters and allow the water to move the fertilizer into the root areas. You should split a large, single application of fertilizer into two or three smaller, monthly applications if you concentrate the fertilizer next to emitters. The bigger the plant, the more fertilizer it needs. Organic fertilizers are better than mineral fertilizers.

Pruning. All major pruning is done during the winter months. Light pruning can be done any time. Prune flowering shrubs -- if you want flowers -- just after they finish flowering. Remove entire limbs or branches, don't use hedge pruners unless it is a hedge. If it doesn't need pruning, then don't prune.

Irrigation. Water plants deeply and thoroughly and then hold back on the water until the next irrigation. I can not think of not a single plant that likes small amounts of applied water applied daily or multiple times per day except mosses, mushrooms and plant diseases.

Trees and large shrubs are watered to a depth of about 2 to 3 feet. Small shrubs are watered to a depth of about 1 to 1 1/2 feet deep. Lawns and flowers are watered six inches to a foot deep. Lawns and flowers are watered most often; small shrubs less often than lawns and flowers. Trees are watered the least often. Desert plants are watered the same way as other plants but less often. The soil is allowed to dry more between waterings.

Change the frequency of application as the seasons change. Winter season is December and January. Spring is February up to May 1. Fall is Oct. 1 to Dec. 1. Summer is May 1 to Oct. 1.

There is the middle of summer when temperatures get above 110F; I call this our extreme summer. I add an extra watering day during this period. Water should be applied to at least half the diameter of area under the plant.

Mulch. Desert plants can be mulched with rock mulch. Nondesert plants require organic (wood) mulch.

Q: We are thinking about taking out our Bermuda lawn and putting in desert landscaping. Should we be spraying the Bermuda to kill it first or just remove it? Should we put down a weed barrier so the Bermuda will not grow back? If we spray it, will the spray kill other plants growing nearby?

A: There is no such thing as a soil barrier that will prevent Bermuda grass from coming back. Removing it without killing it only reinvigorates it.

The best thing I can tell you is to spray this fall with Roundup, kill as much as you can and then remove it. Make sure the Bermuda grass is healthy and growing strong when you kill it. The best months would be late September and through October. The better it is growing, the better kill you will get. Wear protective clothing when spraying and read the label.

Roundup will kill or damage anything green that is sprayed with it. It is inactivated by soils after about ten days so there is very little residual left after spraying.

You will not get all the Bermuda grass. After spraying, wait 24 hours before watering. Then water and fertilize it again and try to get it to grow. Mow it again. Look for areas that were missed with the Roundup and respray all grass areas again.

Continue to irrigate, waiting at least 24 hours after spraying, being careful not to let it get stressed. You can remove the dead grass after it has turned totally brown. When planting trees and shrubs try to remove all sod and soil containing grass roots away from emitters and planting holes by at least 1 foot.

Rock mulch and dry soil will be used to minimize regrowth of Bermuda grass. Spot spraying with Roundup after planting will be used to control Bermuda grass as it appears in the landscape. It will reappear.

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