Q: Can you give me some advice on the planting and growing of tulips, dahlias, iris and gladioli in the Las Vegas area? I recently planted tulip bulbs which I purchased from a mail order catalog and refrigerated for several weeks. Can they be grown successfully here? What would be the proper planting time? Any other helpful tips would be appreciated!
A: Basically the fall bulbs are planted in October, November and December. They include tulips, anemones, ranunculus, hyacinths, daffodils, amaryllis and calla lilies .
Anemones and ranunculus can be planted as early as October. Tulips, hyacinths and daffodils should spend six weeks in the refrigerator and be planted in late November or December. Gladiolus like the spring and fall months but have problems during the summer heat. They like lots of water and good drainage.
Grape hyacinth, sometimes called muscari, does very well here. Put amaryllis on the east side and keep it away from late afternoon sun. You might want to mulch it during extremely cold periods. Cut back on the moisture in late fall and winter so that it will dry down and reflower again in the spring. Calla lilies are difficult here, heavy feeders and need lots of filtered light away from the wind.
Iris does well here. The best time to plant them is early fall and this is the time when the local iris society usually has a plant sale. That is the best source of iris rhizomes if you want a wide selection of colors and types. They should be divided every three to four years.
Gladiolus also does well here .
Contact the University of Nevada Cooperative Extension’s master gardener help line for information about the local iris society and its plant sale. The sale usually occurs at Plant World Nursery on West Charleston Boulevard.
Q: I’ve got an asparagus bed that is doing fair. Last fall it did not go into dormancy completely and I’m worried about what a freeze might do to it. I’m not home all the time and I may not be able to cover it if it freezes. In September of last year I cut off the tops of the stalks but that only prompted new growth from existing stalks. Is there anything I need to do now to prevent them from dying this winter?
A: Asparagus is only cut back after the tops have completely turned brown and died. That is easier in more northern climates but in our climate asparagus may very well have some green in the yellowing stems through the winter. In this case cut them back in January prior to new spring growth and spear production.
You do not need to do anything to
protect asparagus from winter temperatures. The rhizomes are normally planted about 12 inches deep so soil temperatures are fairly consistent at those depths. However, in January and after the tops have been cut back lightly, hoe the asparagus bed to remove any remaining stems from the soil.
You should fertilize with your favorite form of phosphorus fertilizer and apply about a 2-inch layer of good compost or a compost and soil mix. Asparagus needs water in the winter even though it is not growing so you will need to water it about every two to three weeks, especially if rhizomes are deep. If they are not deep, then water more often.
As spears begin to push from the soil, increase the frequency of your deep-water applications.
Try growing white asparagus by covering part of the bed so that no light gets through to the soil where the spears are emerging. White asparagus is grown by excluding light to the spears so that they do not produce any chlorophyll, that green plant pigment . I would do only part of your bed so you can estimate when to harvest white asparagus by looking at the rest of your bed.
Q: My tomato and zucchini plants are growing great guns right now. Unfortunately, neither is producing. I thought the tomatoes would be self-pollinating while I know the zucchini needs help. It may be too late for this year, but is there anything I can learn from this for next year that would help increase a fall yield?
A: Tomatoes stop setting fruit at temperatures above about 95 F as do some other vegetables. So the fruit that did set will continue to grow and you will continue to harvest until that fruit runs out, usually well into July. However as soon as that fruit is picked, you will hit a dry spell in fruit production until temperatures drop down and fruit starts setting again.
There is always a lag in time between fruit setting and harvest. They are still growing so they need some fertilizer applied during these dry spells.
Zucchini will often set fruit without hand-pollination if you have plenty of bees. However, if temperatures are very high, they also will stop setting. But if pollinators are low, then hand-pollination is a good idea.
I would put in a variety of plants that flower so that bees will be more likely to visit your garden. Or put in flowers that you know will flower during hot weather to encourage bee activity. Be prepared to tolerate some damage to tender leaves of your landscape plants from the solitary leaf cutter bee. This should be tolerated as they use these leaves for nesting material.
Q: I have two pine trees about 15 feet apart. They are about 35 feet tall. One is fine. The other is ill. Some of the needles are brown; the good ones are sparse. The tree is losing its outer bark (almost molting) and there is some dried sap showing. Some of the small branches are brittle and can be snapped with some effort. Is this a normal change in the tree?
A: The usual reason for pine trees to lose their needles, demonstrate poor growth and or experience branch dieback is a lack of water. These trees, at 35 feet, are relatively tall assuming they are a tall pine tree species and not Italian stone pine, a short pine tree.
You don’t tell me what kind of pine so I will assume it is either Mondale or Afghan pine. There are other pine trees out there, such as Japanese black pine, that does not do all that well here . So if it is Mondale or Afghan, it sounds like it is not getting enough water.
A pine tree that size might require as much as 50-100 gallons each time it is watered. If it is on drip irrigation, this might be the problem. Even if you give it more water this time of the year, you won’t see much change, but that shouldn’t stop you. Deeply irrigate it now and next spring to see if this makes a difference in the density of its canopy.
There are very few insect and disease problems on these types of pines so I don’t think insects or disease are the problem. When branches die back they are normally brittle and snap easily.
Sap can be an indication of stress and that could be due to a lack of water. Without more information or pictures, it is hard for me to diagnosis more than I have.
Bob Morris is a horticulture expert living in Las Vegas. Visit his blog at xtremehorticulture.blogspot.com.