Nitrogen, iron fertilizers can produce dark green leaves

Q: Thanks to your previous advice I used an iron chelate, applied it to the soil in March, and got my plants to develop a dark green color rather than a yellowish-green color.

A: There are many things that cause a yellowish color in plants besides needing an iron fertilizer or chelate. The plant you mentioned appears to be a native desert plant, a Texas sage. Most native desert plants don’t need an iron fertilizer. They are usually accustomed to our soils and don’t need iron. Watering or a nitrogen fertilizer may be the issue.

Regardless, the two fertilizers that can create dark green leaves are nitrogen and iron. If that plant is native to the Western U.S., then yellowing leaves are more likely issues involving either nitrogen or watering too often.

Nitrogen causes stem growth as well as dark green leaf color. Adding only an iron fertilizer or chelate causes the new growth to become green but does not stimulate new growth that much. When iron is involved, the yellowing occurs on newer growth. Yellowing due to a need for nitrogen occurs all over the plant. Also, the yellowing of leaves due to iron may be a yellow leaf color while the veins of the leaves stay a darker green.

Two types of overwatering can occur: watering too often or giving the plant too much water all at once. It is easier for the plant to resist overwatering from the latter rather than the former. It is easy to water desert native plants too often when placed on the same irrigation line as nondesert plants.

Another reason for yellowing leaves is cold temperatures. This type of yellowing is more of bronzish-yellow leaf color and happens during cold weather. Cold weather damage to mesquite leaves (yellowing or bronzing) is a common occurrence during cold weather just before the leaves may fall from the tree if it gets cold enough.

Q: I’ve been trying to attract bees to my garden and thinking about a hive at some point. I need to put in some year-round flowering plants first. Rosemary comes to mind. Any thoughts or literature come to mind?

A: Rosemary is a good choice. It flowers during the winter and is lower in water use since it is a smaller Mediterranean plant.

Any plant that has conspicuous flowers during early spring and is cold-hardy will work. That is one reason roses work so well.

Other plants to consider that flower during that time and are cold hardy for our climate include the different Texas sage and Tecoma types.

Don’t forget a mixture of annuals and perennials that have brightly colored flowers. Use many different colored flowers like mustards, clovers, desert bluebells and blue eyes.

Scratch the seed into the soil with a rake and start watering them twice a month in December and January with 15 minutes of water from a sprinkler. Turn off the water when your fruit starts flowering.

Don’t forget water. Honeybees like to haul water during the winter as the hive starts to warm up. Bird baths and plastic troughs dug in the ground help attract bees and other critters.

Don’t let the bees drown. Put rocks in the water so bees have a place to land.

Honeybees are active during the daylight anytime temperatures are in the mid-50s, clear and sunny, and little to no wind. Night flowering plants such as some cacti don’t work because bees need to see the sun to fly.

Honeybees are supplemented with sugar water when they can’t find flowers they like. Feeding the colony with sugar water helps to keep the population alive during the coldest parts of winter.

Q: I’m traveling in China right now. I just went past the city of Yunxiao on a bullet train. I saw many trees that I think I have identified as loquat trees, They have some weird paper on all the fruits, and I was wondering if you could tell me what they are? I found your name on the Internet as an expert in the field.

A: I wanted to make sure it was not for a specific pest problem, so I looked it up. Melons are bagged in other parts of the world for melon fly as an example. Pomegranate fruit is bagged due to the Pomegranate butterfly in Central and South Asia. The reason for bagging loquat fruit is for improvement in fruit quality and not for a specific insect problem.

Bagging loquat helps to reduce bird damage later in fruit development, reduces pesticide residues which helps farmers sell in the organic market, helps prevent insect damage or scarring, damage from the sun, and improves the overall quality of the fruit. The cost of bagging must be economically compared to the value of the fruit for sale.

Q: My 25-year-old bottlebrush bush needs some attention. Can I shape it a bit by trimming it back without harming it? The only trimming I have done is clipping off brown ends each spring (none this year) caused by winter cold. It displays beautiful color for several weeks when the weather warms up.

A: Yes, but be careful and don’t let the landscape maintenance clods ruin the plant by shearing it. You only want to create separation between branches. That requires deep pruning cuts, not shears. Shears are for hedges. If it flowers in the spring, then prune it immediately after it finishes flowering.

Use hand pruners and snip three or four branches from each side of the plant, deep inside it, to open it up. Hide your pruning cuts 12 to 18 inches inside your shrub. Because it’s so dense on all sides, cut at a crotch and remove an entire offending branch or stem.

Concentrate on removing stems or branches that are growing down or up. From each section of the shrub remove a stem so the remaining branches are more open and can breathe.

Remove no more than about one-quarter of the branches every three years or so. It will not need more than that.

When you are finished pruning, the shrub should look like it was never pruned. That’s the mark of a good pruning job. Also, now is the time to apply an iron fertilizer/chelate to the soil to cure the yellowing that occurs on this plant.

Q: We recently discovered an invasive plant/vine partially covering the long-established jasmine that covers our back wall. While trying to remove the invader from our raised bed, we discovered that it was not merely a vine with some pretty (yellow) flowers and small, delicate green leaves, but that its root system is producing what looks like tubers. Could you please help us identify this unusual plant?

A: There are quite a few vines that have yellow flowers (if that is the flower color) including cat claw vine, Carolina jessamine and yellow orchid vine. If they are perennials, then they either grow from tubers (like cat claw vine) or swollen rhizomes which grow back from a freezing winter (like yucca vine). To name a few of the vines suitable for this climate with yellow flowers are cat claw vine, Carolina jessamine, primrose jasmine, lady banks rose (yellow form), yellow orchid vine and yucca vine. I don’t know which grow from tubers except for cat claw vine.

I would suggest that you plant the tubers, give them some water, and see the color of the flowers. Send me some pictures of the leaves, vines and flowers, and I can help you more.

Q: I have some old vegetable seeds that I planted. I was told I wasted my money and time. Do you think I did?

A: It depends on the seed, how it was stored and how old it was. Usually, large seed doesn’t store as long as smaller seed, maybe two or three years. Small seed might store for five or six years or longer.

The best temperature and humidity to store seed totals less than 100 degrees. For instance, if the storage temperature totaled about 70 degrees, then the humidity should be less than 30 percent. If the humidity was 70 percent, then the temperature needs to average around 30 degrees.

Of course, the best temperature and humidity for seed storage is as low as possible but having them both total less than 100 is suitable for a couple of years.

When using old seeds, plant two and expect one to live.

When storing seeds, I try to keep as low in temperature and humidity as possible. I use a desiccant (corn starch works OK), put them in a glass jar with a screw lid, and put them in the fridge. They will keep this way for several to many years depending on the oil content of the seed. Small seeds usually has less oil in them than larger seeds.

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