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Irrigation frequency, not amount, varies by season

: I finally got good advice on how to water my trees and bushes this year. I watered one hour twice a week for deep watering during the summer and they have flourished. Now that we have cooler temperatures, I have decreased it to once a week for one hour. Is this correct for now or should I change my watering schedule?

A: Yes, it sounds right. You will change the frequency you apply water per week but not the number of total minutes that you irrigate.

About mid-October everything in the University of Nevada Cooperative Extension Master Gardeners Orchard in North Las Vegas goes to once a week except those plants that still have fruit. This will help the trees without fruit drop their leaves earlier. As soon as the fruit on the trees is harvested, we will drop their irrigation to once a week as well.

Don’t forget to fertilize in late January. A clean way to do that is to use tree or shrub fertilizer stakes pushed into wet soil (just after an irrigation) under the emitters. If your plants need iron (those that tend to yellow), then apply it in the same place at the same time as the fertilizer.

Q: This spring we planted our first-year asparagus crowns here in Pahrump. We now have 2-3 foot tall ferns throughout the bed. When should we cut them back or do we let them die back naturally? We also have received conflicting information on when to start harvesting asparagus. Can you take some the second year or do you have to wait until the third year?

A: For many years it was commonly believed that you must wait about three years before harvesting newly planted asparagus. This is not true.

It has been demonstrated that you can harvest asparagus the same year it is planted, provided the spears are large enough in diameter, and still allow the crowns to survive. Only harvest spears that are as thick or thicker than your pinkie finger. You should be able to harvest for about four to six weeks in the spring.

Allow the thinner spears to grow to their full size, 3-4 feet tall or more, without being disturbed. These ferns are important to rebuild and enlarge the root system of the plant. They are not removed until they freeze back in the winter or, if they don’t freeze back due to our warmer climate, remove them before new growth starts in the spring and compost them.

Asparagus are heavy feeders of nutrients so it is important to fertilize the asparagus beds each year in the spring before new growth begins, as well as in mid to late summer when they are rebuilding their root systems. They like lots of water so water them deeply and as about as often as you would your fruit trees.

But let me back up a little bit. Asparagus is started at the nursery from seed. The seedlings are grown in a greenhouse or cold frame until the crowns or roots are two to three years old. At this age the crowns are sold to gardeners. Good asparagus growers will use this time to eliminate female plants from the nursery since they are not as productive as male plants. You also should be removing the female plants from your asparagus beds.

Female plants produce fruit and seed, which look like round balls the size of a large pea, on the ferns. They are green at first but turn yellow or red when they are ready to split open and spread their seeds. You should remove these tops as soon as you see those green balls.

Seeds, when dispersed by these balls, will germinate in your asparagus beds. Half of these seeds will develop into female plants that, over time, will reduce your production of asparagus.

When you buy asparagus crowns, they will be two- or three-year-old roots ready for modest production. You will plant them in a trench perhaps as much as 12 inches deep if your soil is not a clay soil. They do not like clay soils anyway. When planting, use a heavily composted soil in the trench along with some phosphorus fertilizer to stimulate more root growth.

The crowns should be covered with 3-6 inches of soil and not buried completely until spears begin to emerge in the spring. The soil being applied on top of the crowns then should be heavily composted.

We have grown asparagus here quite successfully with drip irrigation.

Asparagus is an herbaceous perennial, which means its roots survive year to year but the soft above-ground part of the plant will freeze to the ground in subfreezing temperatures. The roots or crowns enlarge each year by collecting sunlight from the succulent above-ground growth.

We try to leave the above-ground part of the asparagus plant alive as long as possible through the season so that it will send carbohydrates down to the roots for storage. In the spring the spears emerge from the crowns, feeding off of the stored carbohydrates. If we cut the asparagus tops down too soon, we will stop the transfer of carbohydrates from the top to the roots.

Even when it is cold, those carbohydrates are being sent down to the roots provided the top of the plant is still green and healthy. If you live in a warm spot, you may cut them back in January or February before the spears emerge in the spring.

Q: I am interested in gardening resources for Mount Charleston, at about 7,500 feet, particularly apples, pears, cherries, blueberries, maples and plants with seasonal colors. Oh, and things the deer won’t find tasty!

A: At your elevation we can expect that temperatures will be somewhere around 25 F cooler than at the valley floor. This is because temperature drops a little bit more than 2 F for every rise in elevation of 1,000 feet. This also corresponds to a climate more similar to places further north.

Generally speaking, you should have very good luck with apples, pears and cherries, but you may have some freezing damage to peaches and nectarines. Many of the Mediterranean fruits, like pomegranates and figs, may have a rough time up there. Your growing season is short, maybe less than 120 days, but in the summer months you would do quite well with tomatoes, peppers and many others. You could use hoop houses or cold frames to extend your growing season to perhaps as many as 200 days or more.

The plants you mention will do well. Since the soils are still alkaline, you will have trouble with plants that do not like our soils. Keep with plant recommendations for the arid West at northern latitudes such as Reno, Salt Lake City and Denver, or for those at higher elevations in the Southwest like Santa Fe.

Deer are a big challenge for you. Generally speaking, the only way to keep them out is fencing. It is thought that if they cannot see on the other side of a fence, they will not jump it. So, they may not try to jump any kind of barrier they cannot see through. This is only speculation. If they are hungry enough, they will be more daring in their attempts to get at food. In that respect, they are much like very big rabbits.

Bob Morris is an associate professor with the University of Nevada Cooperative Extension. Direct gardening questions to the master gardener hot line at 257-5555 or contact Morris by e-mail at morrisr@unce.unr.edu.

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