Delay cutting fruiting grapevine cane as late as possible

Q: I have a 5-year-old Thomcord grape and I was wondering how to prune it properly. I am using it to shade a chicken coop.

A: I have never grown a Thomcord grape so I had to do a bit of reading up on it before I responded. This is a cross between a Thompson seedless and Concord grape. Thompson seedless is usually cane-pruned so I was concerned if this grape had to be cane-pruned or spur-pruned.

The information I got was that it was spur-pruned. The difference between the two types of pruning is the length of last year’s growth left remaining after pruning.

If it is cut too short, there will be no fruit. If it is cut too long, too many bunches of grapes are produced and the berries might be very small.

In the Mojave Desert, wait until about mid-February to finish pruning grapes. Cut the vines back anytime during the winter, but cutting the fruiting cane to its exact length is best when delayed as late as possible. It can be a little scary to wait this long because buds start enlarging several weeks before new growth begins in March.

When spur-pruning, last year’s canes are cut back to one or two buds only. The very courageous gardeners cut them back to one bud. More timid gardeners will leave two or more buds as a safety measure. The more buds that are left, the more bunches must be removed when thinning out extra bunches.

If your grape plant is sprawling everywhere, it is best to establish the oldest growth in some sort of pattern to make pruning a little bit easier. In vineyards, they used trellises to establish a consistent pattern of growth that can be managed more easily. When it’s more freeform such as yours, the oldest growth might be secured to a structure in a fan pattern for instance.

Produce growth for fruiting, in your case short spurs, along these older stems. As this growth for fruiting becomes too long, cut them back to the oldest growth leaving a stub to encourage growth for future years where you want it.

Q: Do I need to cover cabbage during the winter to protect it from freezing? Can my squash make it or should I just pull it up now? Are my radishes OK for a few more weeks?

A: You are grouping together warm-season vegetables with cool-season vegetables. Warm-season vegetables are grown during the warm summer months, while cool-season vegetables are grown during the cool and cold months.

All squash, whether summer squash or winter squash, are warm-season vegetables. They grow best from mid-spring to mid-fall and should be removed in early to mid-fall to make way for the cool-season or winter vegetables. They will die when it freezes but grow poorly when temperatures are low.

They don’t like temperatures below 40 degrees F, so harvest them when night temperatures are expected to drop into refrigerator temperatures. They store nicely in the garage when temperatures are above 40 degrees but less than 65 degrees.

Cold crops such as cabbage, broccoli and cauliflower do very well through light freezing temperatures and into the 20s. They perform better when protected with a light blanket such as a row crop cover.

Row crop covers raise temperatures around plants about 5 degrees and protect plants from wind. They are porous so they let light rain and moisture through but capture heat released from the soil.

Q: I want to plant both a red Bartlett and a Keiffer pear but have limited space. I have read about planting two trees in one larger hole. Do you recommend this method?

A: Planting more than one tree in a hole works well when space is limited and your need for fruit is more for fresh eating rather than canning are preserving. The drawback is it requires extra management on your part to make it work. It is an alternative to having several different kinds of fruit grafted or budded on the same tree.

The disadvantage of multiple fruit growing on the same tree is that these trees frequently revert to only one or two types of fruit in a few years rather than the five or so that came when you bought it.

The mistake made by consumers when trying either of these techniques is not managing the trees correctly. Like owning any fruit tree, they must be managed correctly if you want them to produce quality fruit.

Planting two types of pears very close together in the same hole, for instance, works if you follow some basic rules. Keep them at similar sizes. If one tree grows faster than another, prune the faster-growing tree to the approximate size of the slower growing tree. Don’t let one tree dominate the area given to both.

Protect the space given to a tree and keep them from invading each other’s territory. If there are two trees, each tree is given one-half of the canopy space. If there are three trees together, each is given one-third of the canopy space. Again, this is done through pruning.

Q: I have a 2-year-old jimsonweed that I started from seed. It really grew this year and now all the leaves are gone. Should I cut back the large branches or leave it alone?

A: Hopefully, you are aware that parts of this plant are highly toxic and hallucinogenic so please be careful. It has grown in popularity through social media and promoted for use in some home remedies. This plant can cause kidney and heart failure if mishandled. However, it does have beautiful flowers and attractive foliage.

It is an annual in northern climates, perennial in tropical climates and considered an herbaceous perennial (dies to the ground and regrows from the subterranean crown) in semitropical climates. Start it from seed if it freezes out, winter pruned like lantana or bougainvillea.

In our Mojave Desert climate, the top dies when it freezes and usually regrows from the base in the spring. So, sometime this winter cut it to within about 1 inch of the soil and let it regrow when it is warm. Mulch it through cold weather to give the subterranean crown some protection from extreme cold.

Q: I had nine mature Italian cypresses that all died. Upon inspection, I discovered a borer in the trunks. I think it is the flat-headed borer. Other Italian cypresses in my neighborhood are dying as well. And there any preventive measures? Or will this insect kill all the Italian cypress in the valley?

A: Years ago I believed that the same borers that attacked fruit trees here, flat-headed apple tree borer and Pacific flat-headed borer, were not a problem for Italian cypress. The literature claims these insects are attracted to trees that have trunks and limbs damaged by intense sunlight. Obviously, this wouldn’t be Italian cypress, I thought, because the trunk was protected from intense sunlight.

I was wrong. I received several reports from readers that they believed their Italian cypress was attacked by borers. Browning of the foliage in Italian cypress is fairly common. Spider mites and root rot caused by watering too often can cause similar types of damage.

I asked my readership for help. A reader sent me close-up photos of Italian cypress with damage suspected to be caused by flat-headed borers. I could see from the pictures that it was indeed flat-headed borer damage.

Live and learn. The best protection from these insects is a systemic insecticide applied to the soil around the tree. There are several formulations, but one manufacturer is Bayer.

The product is called Tree and Shrub Insect Control. Follow the label directions and the manufacturer claims up to twelve months protection with one application.

Bob Morris is a horticulture expert and professor emeritus at the University of Nevada, Las Vegas. Visit his blog at xtremehorticulture.blogspot.com. Send questions to Extremehort@aol.com.

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