Most questions I’m getting now revolve around irrigating landscape trees. I think my message about planting in wet soil and keeping plant roots wet during planting has gotten through to most people.
Whenever planting anything in our amended desert soil, make sure the soil is muddy while planting. The soil should stay wet for the first couple of days while these plants are getting established. If you must, build a doughnut from the extra soil taken from the planting holes to hold the water so it stays close to the plant.
When landscape trees are first planted, landscape workers typically install several drip emitters close to the trunk. That is good. Get to know the make of these emitters and how much water they deliver in gallons or liters per hour. These drip emitters are oftentimes color-coded to indicate from the manufacturer how much water they deliver.
During the second year of growth, move drip emitters to about 12 inches from the trunk and 12 to 18 inches apart. As trees and large shrubs get bigger, add additional drip emitters so that at least half the area under the plant canopy receives water.
Landscapers set the irrigation clock to water daily or every other day after planting. That’s good for the first week, but after that, give the plants enough water so they can last at least two days without irrigating. This means you might need to increase the number of minutes on the clock for some stations.
I use a 4-foot-long skinny piece of rebar to determine how many minutes to water. After an irrigation, push the rebar into the soil to judge how deep irrigation water drained. Water young trees and shrubs 18 to 24 inches deep, medium-sized shrubs 12 to 18 inches deep and small shrubs 12 inches deep. If the water did not drain deep enough, add minutes until it does.
Q: We brought this fig tree from Southern California to Pahrump, where it’s colder. I tried to protect it through the winter, but I had to cut it back this spring because it froze to the ground. Four or five suckers are now growing from the base of this tree. Can I still get fruit?
A: Pahrump has a colder climate than Las Vegas so expect figs to freeze to the ground after a cold winter but regrow from the base. Plants that freeze to the ground each winter, whether it’s in Pahrump or Las Vegas, should be grown on their own roots, not grafted onto a special rootstock. If grown on their own roots, then sucker growth will produce fruit the following year.
Expect fruit from figs each year that they freeze to the ground. That’s because fruit is produced on new growth as well as last year’s growth. Figs that freeze to the ground will not produce an early (breba) crop but will produce a later (main) crop on new growth.
When the majority of suckers are 18 inches tall, remove weak suckers at the ground and leave five or six strong suckers growing outward. Fertilize the plant once at the beginning of the season and irrigate so that the soil is wet 18 inches deep.
If you want fruit, furnish the plant with at least four drip emitters 12 to 18 inches from the trunk and cover the soil with woodchips. Fig trees that don’t freeze back and get larger require more emitters than that.
Q: My newly installed Penta bedding plants are dying, and the leaves are turning yellow. They are getting plenty of water. Any ideas what is causing them to die so fast?
A: Pentas, sometimes called Starclusters, are summer annuals grown as bedding plants for their color. The same as any other bedding plants, they don’t like unamended desert soils, bad quality landscape soils or desert landscapes. They abhor rock but grow best in soil amended with good quality compost each time they are planted.
My guess is that the soil used for growing the Pentas was poor quality to begin with or a poor quality soil amendment was added to it. If a poor quality soil or amendment was used, water drainage will cause root rot that will cause yellowing of the plants. If they were planted in February or March, they might have been damaged by cool or cold weather which can also cause yellowing.
Penta bedding plants are from hot, tropical Africa, so they like the heat, must be planted in soils with good drainage and fertilized every six weeks because they love rich soils. They don’t grow well in cool or cold desert soils or planted without a good soil amendment. In fact, they suffer badly when temperatures dip to 40 degrees in the spring or fall, so plant them only when you are confident temperatures are warm and getting hotter.
Add enough good quality compost or soil amendment so that the soil is dark brown, and you can dig in the soil with a garden trowel easily. While amending soil for planting, throw in some 16-20-0 or comparable organic fertilizer to get their roots off to a good start and the plants established quickly.
Irrigate bedding plants such as vegetable transplants daily after they are established and twice a day during the two weeks of establishment. If this is a permanent bed for bedding plants, use half-inch drip tubing about 12 inches apart for watering rather than the skinny laser tubing, which tends to plug. Water with drip irrigation anytime. When using overhead sprinkler irrigation, water between 3 and 5 a.m. to minimize disease problems and water loss from the wind.
If you use a rich, high-quality compost, then additional fertilizer won’t be needed for the first couple of months. After that, lightly fertilize bedding plants monthly with a high-nitrogen fertilizer such as ammonium sulfate or blood meal. If a good compost is used as a soil amendment, then there are lots of nutrients in the soil already.
Q: What can I do to increase the vegetable production in my raised beds?
A: Improve the soil with a high-quality compost once a year, plant at the right time of year, plant the correct distances apart, follow rotation principles by planting in different spots each year and fertilize regularly.
Mel Bartholomew’s book “Square Foot Gardening” is a good start for understanding planting distances to improve production in raised beds, and Dr. Silvan Wittwer’s publication from Nevada Cooperative Extension is a good primer for growing vegetables in the desert.
Each early spring or fall, add a 1-inch layer of quality compost to the growing area and mix it into the soil 8 to 10 inches deep. When you’re finished, the soil should be firm, not fluffy, and easy to dig with a garden trowel.
Rotate or move vegetables to new locations each time you plant. This rotation should last three to five years before you grow vegetables in the same exact locations. In raised beds, that can be as simple as growing tomatoes and peppers at one end of the bed, the next year the other end and then in the middle.
Use recommended varieties. I can’t tell you how many times I’ve talked to people who have grown vegetables from seed they purchased at the local hardware store. Those seeds can be hit and miss unless you know what you are buying. If you want good quality vegetables, pay a little extra money and buy better quality seeds of varieties that you know will work here.
If you take from the garden, you must give back to it. Fertilize the garden lightly every month as you are harvesting. This can be as mineral fertilizer, organic fertilizers or compost.
Q: I’ve planted peas, and though some of the plants are close to each other, they have wildly different results. Some of the peas were doing very well while others not as well. It’s the same bag of peas, same plant date, same watering and same mulching. Why the vastly different results?
A: This is a classic soil or irrigation problem if they are new seed and all the same but some are doing well and others are not. Try amending the soil consistently and looking closely at how the water is distributed to the plants. Poor drainage and cold soil is the kiss of death to peas.
I’m assuming you know that this is not the time of year for peas. They were on their way out a month ago or are really suffering from high temperatures.
Peas are winter crops and should be planted in November through early spring, provided the soil is warm enough. Pull them when planting warm-season vegetables. Unfortunately, they are usually producing well when replacing them with summer vegetables.
Bob Morris is a horticulture expert and professor emeritus of the University of Nevada, Las Vegas. Visit his blog at xtremehorticulture.blogspot.com. Send questions to Extremehort@aol.com.