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Wednesday, May 25, 2011

Butterfly Iris Can and Should be Divided Every Few Years to Keep Them Blooming

Q. We have nine, 12-yr old butterfly irises is 3 groups of 3 that have outgrown their locations. They have grown/spread from their centers to become about 2 ft. in diameter and now only develop little new growth at their perimeters. I've attempted to prune them back by removing their dead center growth hoping that they will regrow from the center but to no avail. I'd like to replace them with some colorful, attractive ornamental grasses that do not grow taller than 3 ft. and don't spread like the irises.

A. I would keep the butterfly iris and just dig them this fall, divide them and replant them. Sometimes called Spuria or Spuria iris, these are some of the best iris for our desert climate and can be quite showy if managed properly. They must be divided regularly.
Some of the spurias originate out of Persia and Afghanistan. Many of these varieties like the high temperatures and dry humidities of the desert but not our infertile soils. They will perform best if they get some relief from late afternoon sun but should be in full sun most of the day.

They do not like rock mulch at all and should never be planted in rock mulch. Always use wood chips (not bark) mulch of two to three inches as a surface mulch to enrich the soil and keep it moist. They must be dug every three to four years and divided to perform well.
And they must be fed regularly as they are heavy feeders during the growing months. This can be done by applying regular fertilizers regularly or using slow release types less often. Fertilize during the bloom period with formulations of Osmocote, Peters or Miracle Gro for flowers.

Divide them with a sharp, sterile knife, cutting the rhizomes at a bud and allowing the rhizomes to heal for a couple of days. Or you can dust them with a fungicide after they are cut. Throw out any rhizomes that do not appear healthy or robust looking. Plant these divided rhizomes about two to three feet apart for solid stands in the future.

Since these iris (depending on the variety) can range in height up to four feet it is best if they are used toward the back of the planting area. When planting or replanting the soil should be reworked with about half compost by volume and add treble super phosphate to the planting mix if you want good bloomers.

Slugs LOVE Stale Beer

Q. I have learned about slugs two years ago and thought I won the battle. I notice my marigold plants are withering. Went out at night with flashlight and YES!!! Found some big fat ones. The next day lifted a decorative plaque which is on the ground and I got the whole army and their children. Horrible. So I am squishing again and putting the snail dry stuff I got from store. I read about beer and wonder if I should do that. Any suggestions?

A. Stale beer works great as a slug bait. Put out a bowl of day old beer in the garden, sinking it slightly so they can get entrance and they die a happy death. Cover it with some cardboard to give them a place to party. You must clean out the former partiers and replenish the keggers frequently.

Converting Gallons to Minutes for Irrigation

Q. Could you tell me where I could find irrigation instructions in gallons rather than hours and minutes? I am having difficulty in calculating how much to irrigate larger established plants and trees.

PET Table for Las Vegas; Months Correspond to 1=January and 12=December, Inches of Water Per Day
 A. No one puts it in gallons because there are too many different manufacturers and rates of deliveries of different irrigation emitters and sprinklers. These can vary from 1/4 gallon per hour (1 liter) to five gallons per hour. Then there are the types that are variable and can be twisted open to give you more or fewer gallons per hour.

You have to figure make the conversion and convert it yourself. It is not terribly hard to do, particularly in drip irrigation. Each emitter is labeled or color coded to the gallons per hour that they emit.

Drip Emitters Color Coded to How Many Gallons Per Hour They Emit
The hardest emitters to figure out are the types that can be adjusted to different amounts of water. Many of these are adjustable between 0 (shut off) to 10 gallons per hour. It seems simple. You just twist the emitter open and it delivers more gallons per hour. But in actuality it begins to defeat the purpose of drip emitters: precision.

Also many of these variable flow emitters are not pressure compensated. If it is not pressure compensated, then opening one emitter and allowing more gallons to flow can affect the number of gallons on all the other non pressure compensated emitters on the same line. This can mean you have to twist open or twist close each emitter along the same line perhaps multiple times to get the flow that seems to be appropriate.

Not only that but these variable output emitters frequently emit so much water so quickly at the higher settings that it results in water puddling and running off to low spots. This is exactly contrary to the reason we should use drip emitters.

Drip Emitters are Precision Applicators of Water
 With many different types and sizes of plants along the same line the next difficulty for most people is to figure out what size (gallons per hour) to match up with each plant along the line.

So this is how I do that. The first thing I do with an emitter line attached to a single valve is determine how many hours or minutes the valve will be left open for watering. Frequently for drip irrigation the shortest time is one hour.

"Yikes" you might say because most people want to irrigate fifteen or twenty minutes. The problem with these short irrigation times is that it may force you to use the variable output emitters. Or it results in water applied so rapidly it does not penetrate the ground and instead runs and puddles somewhere else.

Start with a minimum of one hour. In some cases you might water for two or three hours on a single line. What difference does it make? You are not standing there with a hose and it can take all night if you want it to.

There is no problem watering at night with drip irrigation. Let it soak long, slowly and deeply. Try to use at least two emitters per plant in case one plugs. Distribute the emitters under the plant canopy, one foot from the plant with distribution tubing and secure them in place with rock mulch or stakes to hold them in place. Emitters should be above the mulch so you can check them for plugging. Plants that are spaced closely together can and will get water from each other.

Lantana Froze to the Ground

Q. This winter I had a low temp of 25° F at my house. So far I have a couple of sprigs coming out of two cut back Lantana and four with no sign of life. What's lantana's low temp tolerance?

Freeze Damage to Bougainvillea
A. It is not just simply a matter of what the low temperature was. Plant losses due to freezing temperatures involves how low the temperature got, the time of year low temperatures occurred and for how long or how many hours. Relatively mild freezing temperatures can cause considerable damage if they occur early in the fall or late in the spring.

Also, 25° F can be much more damaging if it lasts for 1 hour vs. lasting for 15 minutes just before sunrise. On top of this, freezing temperatures accompanied by strong winds will be much more devastating.

You should have seen some new growth coming from the base of the plants by now. If not, you will have to replace them. This winter was hard on lantana and, in some locations, they did freeze out or severely die back.

In the future, you should be able to cut them back to 2 to 3 inches in height and they will come back nicely. Don’t forget to fertilize with a good quality fertilizer that encourages flowering such as a rose fertilizer, tomato fertilizer, fruit tree fertilizer, etc.

Almonds Turning Yellow and Dropping

Almond Nut Sap Oozing and Dropping
Q. I'm having an awful time with my almond trees. I have two and they are about 8 years old. Last year my tree had large almonds and was just covered with nuts. Well, I lost all of them. They have a see through something coming out of them and then they open and have this yellowish design on the inside. Then they drop. In the meantime my almonds are falling off. So far this year I applied Volck Oil Spray when they were dormant and two weeks ago I applied a fungicide.

A. Thanks for your pictures. Several people have visited with me about the same problem. The squiggly resin coming from the nuts is usually a sign of feeding damage by insects which have mouthparts like a hypodermic needle. They stick this needle into the skin of the nut or fruit, feed on the sap and withdraw it. When they withdraw the needle it leaves a hole in the skin and sap comes out and dries in the squiggly clear resin that you see.

Leaffooted Plant Bug

Sometimes the feeding damage by these insects can cause the nut or kernel not to form. This can result in husks with no nut and the almond yellows and falls from the tree. If this happens to a few nuts and hundreds still remain on the tree then it’s no big deal. But if this happens to hundreds of nuts then this is a big deal.

One of the culprits is the leaf footed plant bug or one of its relatives and you should keep an eye out for this pest. It is a bad one.

Another possibility could be a lack of pollination due to low temperatures during flowering or a lack of good fruit set. We did have some late freezes and if the flowers were open during freezing temperatures it might be possible they were damaged and you lost some of your crop. I do not believe you needed a fungicide spray. My strongest hunch is an insect problem if this happened to you two years in a row.

Asparagus Not Coming Up in Third Year

Asparagus Started From Seed in a Trench
Q. I had an 8' x 1' garden box patch of asparagus which this year would have been the 3rd year of growth. Everything was fine the first 2 years but nothing grew this year. I pulled up several roots and noticed they are like straw - empty in the middle. I do not think I overwatered. The only thing I did different was I started emptying my daily coffee grinds in the garden patch. Do you have any idea what happened or was the cause?

A. The coffee grounds would not have made any great difference either way. Asparagus can be planted from crowns or seed. I have had great luck both ways and particularly like starting asparagus from seed.

We use an irrigation trencher and set it at its deepest setting, usually about 18 inches deep. We then backfill the trench about 8 to 10 inches with heavily amended soil from the trench, minus large rocks. The soil taken from the trench is heavily amended with compost made from animal manure, in our case horse manure.

This compost is left to finish composting for about 4 to 6 months. This means this mixture of manure and plant waste is turned regularly and watered so that everything breaks down together. This finished or nearly finished compost is added to the soil removed from the trench in a mixture of about 3 to 1, compost to soil.

This compost/soil mixture is then added to the trench as I stated above. On top of this layer we will spread a high phosphorus fertilizer such as triple super phosphate to enhance root development. We will spread about one hand full of this phosphorus fertilizer every 3 to 4 feet in the trench.

Asparagus crowns are then placed in the trench and covered with amended soil from the trench. This is usually about a 50/50 mixture of compost and soil minus large rocks. If you leave large rocks in the trench above the crown it can cause crooked spears.

It is important to dig the trench or bed much deeper than the crowns or you will create perched water table just above the unamended soil. This perched water table can drown the asparagus crowns and cause them to rot.

From your description that is what it sounds like. I would be careful planting asparagus in that same location. I would find a new spot and dig a trench or bed much deeper than you need to for drainage.

Some Scarring of Apricot Probably Not Due to Thrips

Q. I have some damage to my apricot fruits and sent you a picture. Is this damage from thrips? I have a nectarine and an apricot tree. Once all the fruit is off the tree what is the best way treat the trees? From reading your newsletters I understand thrips are hard to eliminate. At this point I would even consider a non organic method. Not all the fruit was affected, but many with a minor markings. I removed and disposed all the fruit from the nectarine tree very early as all fruit was badly damaged.
Aprcot Scarring Sent from Reader