Water plants deeply to reduce temperature stress


The current high temperatures will have a big effect on plants’ water use and stress. Make sure landscape plants are deeply watered during this time of high stress. It is best that plants enter into the heat of the day with plenty of water rather than applying it at the end of the day.

Q: How does one start new sago palms? I have a few fronds coming up at the base of our mature sago. What is the process for getting them to live after transplanting?

A: In the past, sago palms were never very popular among nurserymen because they had a hard time making money from them. They were slow to grow to a marketable size and had a reputation for being hard to propagate from seed. They can be grown from seed, divided stems and pups.

For you, the best way to propagate it will be from side shoots or pups. These are carefully cut from the stem with a sterile knife, dipped into rooting hormone and then placed in a soil mix that easily drains, and out of direct sunlight, for rooting. They need lots of light but it should be indirect light .

In our climate it also is a good idea to make a plastic bag greenhouse (clear plastic) for them to help keep the humidity high until they root. Rooting can take a long time so as long as the pup remains healthy, leave it in the propagating soil mix. Once rooted, you should see new growth.

You might also increase your chance of success if you dip the pup into a fungicide, such as thiram, captan or zineb, to prevent rotting. As an alternative to a fungicide you can let the pup air dry for a couple of days inside the house .

Once the roots have formed it has been suggested that cycads respond well to fertilizer applications of nitrogen and potassium.

Make sure you let wounds in the main trunk heal before you let any soil come in contact with it .

Q: I have two gardenias in the backyard in 15-gallon ceramic pots with good drainage. One of them is doing pretty well and the other not so well. Our backyard is on the north side so both are shaded most of the day. The picture I sent you has leaves turning yellow and then brown on the interior of the plant although the ends of the branches still have green leaves. Both plants are on drip (irrigation) and watered the same. I added iron on top of the soil and Vigoro 10-8-8 plant food but it doesn’t seem to be helping. The one I planted about six weeks ago has not done well. The other one was planted three months ago and is doing well . Any suggestions for the one with the yellow leaves?

A: My best shot at the gardenia is iron even though you added some. If you don’t use the right iron, it may not work.

Use an iron chelate such as EDDHA with iron. You can pick up a 1-pound canister of this at Plant World. I don’t know any other place where it is sold. Combine it with a soil application of your Vigoro fertilizer.

Try to use fertilizers specially made for gardenias in the future, if you can find one. If you can’t, use one for azaleas and rhododendrons. If you can’t find that, a third choice would be to use one for tomatoes, fruit trees or roses.

Whenever you are watering a plant in a container, you want to add enough water so that about 20 percent of the water runs out the bottom. This helps keep salts leached from the soil. Tap water coming from the Colorado River is quite salty and you need to make sure the soil stays flushed of salts coming from the water. If you don’t, these salts will build up in the container’s soil and cause exactly the problem you describe.

You can’t let the soil go dry so it might be a good idea to buy an inexpensive soil moisture meter used for houseplants that can give you a rough idea when you should irrigate. Another way is to judge it by its weight. You don’t have to lift it, but just budging or moving it a little can give you an idea.

You want the soil to dry between waterings, but not too much. If it doesn’t dry down, you may develop root disease problems on gardenias. If you let them get too dry, they will drop leaves and the remaining leaves will scorch.

Q: I have four sago palms and two are turning yellow. The two that look best were bought from a local nursery and the two that don’t were bought from a building-product mass marketer. They are all planted in rock mulch and watered on drip irrigation. They get about 15 gallons each a week. They are now pushing new growth. I screened the soil they were going into when planting them and put in a lot of peat moss to amend it. They get sun all day long. I tried some local supplements but they don’t seem to be helping.

A: On your cycads, or sago palms, it is stress. It looks like the yellowing is from high light combined with high-temperature stress. The rocks are not helping since the radiated heat makes the area hotter.

Put some shade over it but the damage is done . You have to rely on new growth to cover the damaged growth .

Sagos will not do well with rock mulch. They don’t do well if the soil doesn’t drain easily either. They really want to have rich, organic soils, mixed with their roots, to do well. Even though they are somewhat tolerant of dry soils, they are not drought tolerant.

The worst exposures for sago palm will be hot south- or west-facing exposures near heat-reflecting walls with rock mulch at their base. The best exposures are east or north exposures with lots of indirect light with wood mulch at their bases and plenty of air movement.

Be careful of watering too often since they will get root rot if the roots stay wet for too long .

Bob Morris is a horticulture expert living in Las Vegas and professor emeritus for the University of Nevada. Visit his blog at xtremehorticulture.blogspot.com.