: I am hoping you can shed some light on our problem with vinca. We are growing it in containers. This is the first year we have had problems with it.
A: Vinca minor is a good evergreen groundcover in partial shade; it has small spring blue-purple flowers. There are several things I can tell you regarding vinca.
First, there are a lot of different diseases that can attack this plant. There are about three that just attack the roots. If you have any of the root diseases, the plant will die fairly quickly after wilting. If vinca dies from root diseases, you should be able to see dark or rotten areas on the roots. Healthy roots should be off white or cream colored.
A lack of water also will cause vinca to wilt. The plant will wilt, you will water it, it springs back to life and then wilts again when it needs water. If you do not catch it in time, it will die from a lack of water.
As far as the container goes, if the container is too small, it will lose water rapidly and get overly hot in our climate. This can cause the plants to require more frequent watering or the soil in the container may become so hot it can damage the roots and they may die.
Vinca will do best in a well lit but partially shaded area. It should be planted away from direct and intense midday or afternoon sunlight. It prefers a well-prepared soil that is moist. Containers will need frequent watering with good drainage during the summer.
Q: I read somewhere that a mixture of 50 percent sulfur and 50 percent 15-15-15 fertilizer applied at the end of the year should take care of soil salts and improve the soil. I’m trying it now, but it seems that the sulfur won’t dissolve, even after several waterings.
A: The only thing that will get rid of salts is running water through the soil. Water will dissolve the salts and, as long as the water can drain, straight water will flush salts out of your soil. As far as taking care of soil salts with a mixture of sulfur and fertilizer, that is hocus pocus.
Good indicator plants for salts are bush or pole beans as well as radishes. If you can plant beans and radishes and their leaves do not scorch, the salt problem is minimal.
Sulfur applied to the soil in granules can take years to dissolve. The more finely ground the sulfur, the faster it will dissolve. It needs moist warm soil to dissolve and start lowering the soil pH.
Q: It seems like my garden produced more right after I put it in about six years ago.
A: For a good productive garden you should be adding 2-3 inches of rich compost every time you plant and tilling it in.
Remember to rotate the plants in your garden. Do not plant vegetables of the same family in the same spot year after year. Rotate them to different locations. Tomatoes, eggplant, peppers and potatoes are in the same family. Melons, squash and cukes are in the same family. If you do not rotate the plants, you will see declines in production.
Q: My eggplant ripened when I was out of town and has started to turn golden. Is it still good?
A: There are a few things that could cause yellow eggplants. First of all, there are white eggplants, like the Thai yellow egg that will turn yellow if left on the plant too long and overmaturing. The solution is to harvest earlier.
Most eggplants need to be harvested when young. Letting fruit get larger than needed will slow down production from the entire plant. Smaller fruits are usually more tender.
Of course if these were producing black eggplants prior to the yellow ones, then it is not one of the white-fruited plants. Eggplants like Black Beauty, probably one of the most commonly planted varieties, will occasionally have fruit that will turn yellow and hard when overmature. Again, you need to harvest on a regular basis when the fruit is small.
Another possibility is insect problems. Insects that burrow into the fruit and lay eggs will cause the fruit to be misshapen, usually get holes and turn yellow. Sanitation would be a good idea. Keep the area clean from old garden debris.
Q: We have two Mondell pine trees that we planted about four years ago. They were about 20-25 feet tall when we planted them. They are now about 35-40 feet tall. During the last two weeks, we have noticed that the needles are turning brown and falling off at an alarming rate. Is this a normal process? If not, what should we do?
A: No, this is not normal. There is a certain amount of needle drop that is normal every year; however, when pine trees lose their leaves and the canopies become thin it is normally due to a lack of water. If these trees are on drip irrigation, my guess would be they are not receiving the volume of water that they require. I am guessing that trees of that size will require somewhere around 90-100 gallons of water per week during the summer.
Typically trees like this will do well in the spring and fall months but suffer during the heat of the summer when their water requirements might be twice as high. The easiest way to water trees of this size is to construct level earthen basins around the trees, perhaps 6 feet in diameter and at least 3-4 inches deep.
These basins are filled with water at each irrigation, allowing the water to penetrate into the soil 18-24 inches. If you are using drip emitters, you will still have to apply the same amount of water, which means you will have to run the drip emitters several hours to deliver this amount of water.
As trees get larger they will require more water and so you must add more emitters around the trees to accommodate their larger root systems and increased demand for water.
Giving these trees more water at this time of the year may not increase the density of their canopies until next year. But, you must give them enough water to support their growth and development.
In the spring of each year you should be applying an all-purpose tree fertilizer such as 16-16-16 around the basin of the tree but away from the trunk. If you are using drip emitters, you can apply the fertilizer under the emitters and let the water wash the fertilizer into the root zones.
Bob Morris is an associate professor with the University of Nevada Cooperative Extension. Direct gardening questions to the master gardener hot line at 257-5555 or contact Morris by e-mail at email@example.com.