Plant onions from seeds through November

Q: I would like to grow both yellow and red onions. When is the best time to plant them?

A: Onions for bulbs or green onions can be planted from seed mid-September through November. Onions produced from sets or transplants should be started in March. They can be grown in a garden spot or 5-gallon containers.

Let’s focus on fall planting using onion seed. Growing onion from seed to produce green onions or transplants does not require very much space. Seeds can be spaced close together, so I’d broadcast the seed, or sprinkle them, in the area where you want them to grow.

For green onions, just about any onion will do, so shop for inexpensive seed. If you are growing transplants from seed, be more careful in your selection. I prefer sweet or specialty onions for transplants.

Varieties such as Candy, Vidalia, Walla Walla, Cipollini, Red Marble and Red Longa always do well in our climate and latitude.

Before planting the seed prepare the soil to a depth of 12 inches. Make sure the soil is not “fluffy” — pack, roll or compress the soil lightly to make a firm seed bed.

Onions for transplanting or green onions grow well in containers or in blocks. They do not need to be planted in rows unless planting them to produce bulbs. Carefully scatter the seed on top of the soil and cover the seed with about ¼ inch of top dressing or mulch.

Water the top-dressed are mulched area twice a day. Fertilize them after you see the onions begin to emerge. Then reduce your watering to once a day.

Q: My vining roses have bright yellow, wimpy leaves. Am I over watering? Underwatering? I have fertilized, added sulfur and iron, too. What’s going on?

A: Whether a plant is overwatered or underwatered is difficult to gauge remotely. From your description, it sounds possible you are overwatering but probably not underwatering.

If you are underwatering, I’d expect to see more leaf scorch and dieback. The yellowing is called chlorosis and can come from a number of sources including overwatering.

When yellowing or chlorosis is caused by a lack of available iron, we will call it iron chlorosis. Chlorosis because of iron usually has yellow leaves with green veins. When iron is severely lacking, the leaf may be entirely yellow and scorched, but these are extreme cases.

Surround your roses with wood mulch, not rock mulch. If these plants have rock mulch surrounding them, rake it back a couple of feet and apply a couple of inches of compost first followed by some wood mulch. In this particular case, do not use decorative bark mulch until the plants begin to recover.

Apply an iron fertilizer in the form of an iron chelate before you cover the soil with mulch. The chelate should be in the form of EDDHA listed in the ingredients. The type of iron you add is very important. Mix the iron chelate in a bucket of water and pour it all over the soil above the roots.

Also, fertilize with a rose fertilizer or a fertilizer formulated for flowering trees or shrubs. Avoid watering daily and try to give your woody plants a couple of days rest from any additional water before you irrigate again.

Always keep wood mulch a few inches away from the trunk of any plant to prevent stem diseases from occurring.

Q: We have a gorgeous, shiny, dark green star jasmine that’s more than 25 years old. About five years ago, it stopped blooming and nothing we’ve done has helped. Any thoughts?

A: When that happens to older plants of mine, I usually cut them back pretty hard and try to get them to regrow again, getting rid of some of the older wood.

Sometimes cutting the plant back restores some juvenility and the plant responds by growing more vigorously and flowering. I would also give it a good shot of fertilizer if you haven’t already, and soak the roots with a hose a few times, a few days apart.

It’s late in the year to be pushing new growth so you could try this in early spring instead. However, star Jasmine is pretty hardy in our area so fertilizing it now should not affect its cold-hardiness. It will respond with a flush of new growth next spring without any applied fertilizer.

This is a technique called late-fall fertilization. Fertilizer is applied in November before the leaves drop. If you combine late-fall fertilization and cutting the plant back, cut back first and then fertilize, not the reverse.

Let me know if this works for you.

Q: What would make my San Pedro cactus lose its color? It is becoming pale.

A: Not all cactuses are the same; they cannot be treated the same. The San Pedro cactus, coming from the mountains of South America where the soils are a lot richer and there’s much more water, needs different care than cactuses native to the Mojave Desert.

This particular cactus will do much better in well-prepared soil at the time of planting, much like you would prepare the soil for landscape trees and shrubs that are nondesert. This type of soil should be rich but also drain water easily.

Also, irrigating this type of cactus is different. They have to be watered more often than cactuses native to the Mojave, Sonoran or Chihuahuan deserts that have a history of water that is not available for long periods of time.

The type of cactus will also do better if protected from late afternoon sun. It likes to have lots of direct sunlight, but prefers it during the morning and early afternoon hours to look its best. This cactus also will do better if it is not in an area open to cold winter winds.

If you don’t keep up with your watering, San Pedro cactus will begin to yellow or bleach out. In severe cases, it may even scorch and die back. Some people react by giving it more water. But this could kill the plant if the soil doesn’t drain easily.

Consider moving the cactus, replanting it with a soil that is sandy and gravelly and amended with compost. Make sure the area has deep soil that drains easily. Fertilize it once a year.

Give the cactus is much sun as possible but try to avoid direct sunlight after 2 p.m. See if you can find a place out of winter winds. Water it about every two weeks when temperatures are above 100 degrees Fahrenheit.

Q: When is the right time to trim back the desert princess flower and purple sage bushes and also how far down?

A: I don’t know a plant called the desert princess flower. If you can send me a picture maybe I can identify it. I also do not know a plant with the common name of purple sage. I’m wondering whether this is Texas sage or Texas ranger which is not a true sage.

The general rule for pruning flowering woody plants is to cut them back after they finish flowering. So, if a plant normally flowers during the summer and fall months, we would prune it back in the winter. If a plant normally flowers in the early spring, we would cut it back in late spring or early summer when it has finished flowering.

If these are small, flowering woody plants, we cut them back to within a couple of inches of the soil. If these are larger woody plants, we remove the oldest or woodiest stems deep inside the canopy.

When pruning this way, it is customary to remove no more than about one-third of the total plant in a single pruning.

If the shrub is still unsightly or overgrown, the following year we again remove one third of the shrub.

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. Send questions to extremehort@aol.com.