Getting poinsettia to bloom can be tricky

Q: I have had a large poinsettia since last Christmas. Is there a way to encourage blooms this year? It seems I read somewhere to put it into a dark place without water for a period of time. Anything you can tell me will help.

A: Yes, but you should have started in September. Getting a poinsettia to bloom precisely during the Christmas season is a little tricky. They require the exact amount of darkness, every day, with no interruptions from light while they are plunged into their darkness.

Not even a little peek at them or a door opening to a closet while it is dark. One little peek when it is supposed to be dark can prevent your poinsettia from changing color. Just buy a new one each year. It can be a real headache trying to make this happen.

A poinsettia will change its color when it receives more than 12 hours of total and absolute darkness for three months. For instance, keep the plant in complete darkness between 5 p.m. and 8 a.m. daily from the end of September until the leaves begin turning color (early to mid-December). Then it is safe to turn the light back on.

The temperature should remain between 60 and 70 degrees F. Night temperatures above 70 to 75 F may delay or prevent flowering. Growing poinsettia in low light may cause leaf drop. Growing them without enough water or too much water can cause leaf drop. Growing them in cold temperatures can cause leaf drop.

Growing 100 of them in a greenhouse is relatively easy. But growing one plant in isolation can be a headache.

Q: How long can I leave ripe lemons on the tree? Will they rot or drop? It’s a Meyer about five years old.

A: It’s best to harvest them as they are ripening over a four-week period. Snip them from the tree with sharp pruners or scissors, leaving a very tiny attachment from the stem remaining on the fruit.

Removing this tiny attachment causes an open wound on the fruit. It might seem unimportant, but this wound is an opportunity for rotting organisms to enter the fruit and cause early loss.

Lemons don’t improve after they’ve been picked, much like figs, grapes and cherries. Once you’ve picked the fruit, that is the best it can be. I wash the fruit and put them in the refrigerator in a loose plastic bag to keep the humidity high and temperature low.

Pick them as they start ripening during the winter, usually December in our climate. You can pick them for three to four months.

Leave them on the tree no longer than the first part of January. Leaving them on much longer than this might interfere with flowering and fruit production in the next production cycle.

Q: I just read an article you wrote about overseeding a fescue lawn, and I had a couple questions. Is it possible to overseed a lawn in December? I have a fescue lawn that has Bermuda grass, and I just can’t seem to get rid of it. Will overseeding help with this as well? I mainly want to keep my fescue green all year, which is why I want to overseed.

A: Overseeding a lawn will not help control Bermuda grass or help it stay green through the winter. Mowing at the proper height, along with some added maintenance care and applying a high-nitrogen fertilizer just before cold weather sets in, are the best preventive measures.

Soil temperatures should be at least 60 F for fescue seed to germinate in a timely fashion. Seed germinates faster with warmer temperatures. Unless the lawn is in a very warm location — a warm microclimate, let’s say — it is too late to overseed after temperatures become cold.

Bermuda grass needs sunlight to invade a lawn. Mowing a tall fescue lawn less than 2 inches, and edging it with a line trimmer so that the grass is short or damaged, will increase the chance of Bermuda grass invasion.

Applying a high-nitrogen fertilizer in late fall (around Thanksgiving in our climate) keeps existing fescue green through cold temperatures in winter. Even applying just 21-0-0 now, in early December, will help if you missed the Thanksgiving application.

Q: I am planning on an herb garden in the spring, but there are rabbits in the neighborhood. Which herbs would be most rabbit resistant?

A: When growing vegetables and herbs next to the open desert, I have had to contend with jackrabbits and desert cottontail rabbits. The most effective way of controlling these varmints is to erect 2-foot-tall, 1-inch hexagon chicken wire fencing around the beds. In other words, exclude them from the growing area.

Bury the bottom edge of the fencing about an inch into the dirt, so they can’t get their noses under it. Keep the fencing tight. I have seen baby cottontails exit fenced gardens through 1-inch hexagonal holes of chicken wire at a dead run when they were very young. Sometimes, when young bunnies get in and hide in these beds, they get fat and can’t get out.

Personally, I would not rely on a list of so-called rabbit resistant plants unless there are lots of other plants for these varmints to choose from — like your neighbors. I have found that when bunnies get hungry, they will eat plants that are supposed to be resistant to rabbits.

Q: A few weeks ago my purple sage plants started turning yellow. I’ve cut back on the drip system to three days a week, 15 minutes at a time. A local nursery told me to add iron and acid liquid, which I did. It’s not looking much better. From the picture I sent, can you identify the problem?

A: Some people might know this plant as Texas ranger. Because the plant is not growing during cold weather, any improvements to the plant’s health won’t be realized until next growing season. But I can see several things going on in the picture.

Texas ranger is a desert-adapted plant native to the Chihuahuan Desert of northern Mexico and stretching into Texas. It can handle low amounts of water, high temperatures, low temperatures, low humidity and relatively poor soils. Let’s keep those points in mind as we work through these problems together.

You have several of them planted together as a hedge. I can see they have been pruned repeatedly with hedge shears. Texas ranger can handle hedging, but repeated pruning from hedge shears is taking its toll.

Repeated pruning at the same location with hedge shears causes the plant to become very dense on its outer surface but increasingly woody inside the hedge. Plants can handle hedging for a few years, but the “woody” stems inside start to show through.

The soil surrounding these plants is all minerals with no organics left in the soil that would improve plant health. Any kind of plant health problems causes leaf drop and exposes woody stems on the inside. Unhealthy plants cannot handle cold and hot temperature extremes as well as healthy plants.

I think you are seeing the result of repeated hedge shearing, diminishing nutrients in the soil (because there is nothing organic added) and cold weather leaf drop. Adding fertilizers without amending the soil with organics will not improve the plant much.

What to do? Your options are to make some corrective changes to the plants or replace them. Making corrective changes will make the plant look bad for a while but eventually will improve it.

Shear the hedge 1 or 2 inches to the inside of its canopy, back to the woody interior. This will cause new growth to appear next spring just beneath the woody, sheared surface. This will provide a new, young surface to shear for a few years.

Apply compost to the soil surface surrounding these plants and cover it with woodchip mulch, rather than bare soil or rock. It’s a desert-adapted plant, but even these plants grow better with a smaller amount of organics in the soil.

The other option is to replace these plants with a different plant that handles hedge shearing better.

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.