Gaining control over this annual weed is not easy to do

Q: I have a pretty good stand of mallow coming in. I had a few errant plants earlier that got pulled. What should I do about this?

A: I am assuming you want to get rid of it. Some people like to enhance its growth and keep it. Controlling it is not that easy to do.

Common mallow is an annual with rounded leaves, so it comes back from seed every year. To make sure it doesn’t return you have to interrupt the seed-to-flowering-plant cycle at least for a couple of years and then fill the voids with something competitive like mulch or more flowers. It likes openings and bare wet or moist soil. It hates being competitive in its growing space.

Unfortunately, you are left with pulling it from between the flowers or selecting a general systemic killer (e.g., glyphosate) and using it selectively (painting each leaf of the offending weed). Or you can kill everything in there (roots and all) and start over.

Dicots (like mallow or the flowers) growing alongside each other are not easy to control. Grasses (monocots) that you want to keep, growing alongside a dicot weed like mallow, are easier to control with chemical sprays like Fusilade or Goal. (Those chemical sprays leave the more desirable monocots like grasses, but kill the dicot weed.) But not dicots mixed together with other dicots. That’s very difficult to control with chemical sprays. Even monocots mixed with other monocots are easier to control with chemical sprays.

Why? Any dicot plants in there interfere with any chemical or herbicide spray and does not make it easy to control by spraying. Nothing has evolved for landscapes from agriculture. Agricultural sprays haven’t gotten there yet.

Q: The lantanas in my yard look healthy. But the ones in the pot don’t look as good. The ones in the yard get more sunlight. Could that be the problem?

A: It might be sunlight, but most lantanas will take full sun. Perhaps it’s not enough water, or they may need to be repotted with fresh soil (the organics have run out). Try more water first. That’s easiest. If that doesn’t work, then try repotting it with fresh soil.

Lantana is the name of an entire genus of plants. There are many different species. Lantana camara and Lantana montevidensis are two of the more common species used for landscaping in the desert. Some are smaller. There are about 150 species of lantana, each with different sized plants and flower colors.

I am assuming the variety in the container is one of the smaller lantanas and grows in your landscape. Lantana is a versatile plant that can be used as a ground cover, in containers or as a shrub.

Production nurseries usually take softwood cuttings from new growth. Seldom is it started from seed. Lantana is a popular choice for landscapes in Nevada because it tolerates our desert’s alkaline, salty soils.

Lantana needs supplemental watering in the summer. Do not let the plant dry out. It is not a desert plant, but mesic in its water use.

Prune lantana at the end of winter or when there’s no longer a threat of frost. Remove leaf drop and dead branches by pruning the plant a few inches from the ground after the threat from winter cold has passed. Some find the hairs of the plant irritating to the skin. The fruit and flowers are toxic to humans and pets.

Q: I have a fig tree with branches that are dying and leaves becoming sparse. I have two others doing well. Should I be concerned?

A: Yes, you should be. The most common reason for leaf drop in fig is a lack of water. These trees require lots of water to be full and productive. Not daily watering. That is too often. Water every other day when it gets warm and then hot. When you water, make sure the roots are wet to a depth of 18 to 24 inches (deep watering). In the summer, I would suggest watering them, like any fruit tree, three times a week.

I consider fig trees to be oasis plants, much like palms. While producing figs they should never be totally dry. This means some deep watering with lots of gallons each time. Their need for water depends on their size. I would be watering no more than once a week right now in a 3- or 4-inches-deep, level basin. Make it large enough to be under at least half of the canopy.

If they are on drip and, for example, 6 to 8 feet tall, I would make sure they get about 25 gallons at each watering. If they are all on the same irrigation system and you see some emitters not watering when the water is on, check for plugging of the drip emitters.

Q: I have a 6-by-3-foot raised bed with an acidic soil and a Baba berry raspberry plant, an O’Neil southern blueberry and three varieties of strawberries. There are about five fruiting canes of raspberries with maybe eight new canes this year. I have used osmocote and azalea fertilizer in the spring. There are about six 2-liter emitters each that run for one hour in that bed four days each week. I see that the fruiting canes have yellowed with distorted leaves with brown margins. Some of the canes are looking yellow with green veins.

Am I right in thinking that the fruiting canes will not bear fruit this year but every year thereafter because of the desert? Or have I encountered a disease or killed them with kindness. I thought I would move the strawberries and give the patch over entirely to the blueberries and raspberries, but with the drying out of the raspberry flower heads I’d say the raspberries are the ones to pull out for good.

A: Another person also told me they had some success with Baba berries in Las Vegas. It is recommended as a raspberry for Arizona gardens.

Raspberries are difficult to grow in our hot climate mostly because of low winter temperatures and high light intensities.

All raspberries are biennial plants. In other words, it takes two years to grow fruit and then they die. It isn’t because of the desert. That’s the way berry plants grow.

Raspberry plants do best in soils that are more acidic than we can normally provide. One major problem has been iron chlorosis, which can be corrected with compost and an iron product applied to the soil once a year in the early spring. Add organics (compost) to the soil, use wood chips as a surface mulch and add granular sulfur to moist soil.

I believe you are headed in the right direction by choosing a specialty fertilizer for azaleas. Azalea fertilizer is normally formulated to provide acidity after its application. However, I am not surprised at your results when using this fertilizer among the strawberries without soil improvement. Getting the soil pH a little below 7 helps make iron available to the plant.

We have had some luck with strawberries in Southern Nevada. The biggest question to answer on strawberries is which varieties work best in our hot, desert climate. One that did reasonably well for me was Ozark Beauty.

Bob Morris is a horticulture expert and professor emeritus of UNLV. Visit his blog at xtremehorticulture.blogspot.com. Send questions to Extremehort@aol.com.