SEPTEMBER
2010

 

 

 

By
B. Rosie Lerner
 
Purdue
Extension
Consumer Horticulturist

 

 

 

 

 

09-02-10

Question and Answer


Q. We have a raised bed that is about 7 inches deep. The soil is dark-colored and was excavated from the foot of a slope in a woods near a graveled road. I also added several bags of muck topsoil. 

I have tried to grow several vegetables, but the stems of all are very elongated. Radishes were about 18 inches tall with very small underground parts. Lettuce was about 12 inches tall with small leaves. Tomato vines are about 6 feet tall with thin lateral branches about 5 to 8 inches apart. A few tomatoes have developed near the ends of the vines. I have tied the vines to trellis. 

I have fertilized the tomatoes but not excessively. I have watered when needed. Other flowers, grass and shrubs growing nearby on the natural soil, which is shallow to clay, seem to grow normally. What could be causing this strange growth pattern?

A. Since you are getting a lot of presumably healthy foliage growth but poor root and fruit development, I would suspect low potassium and/or phosphorus. If you have not yet had the soil tested for nutrient status that should be your next step. The Purdue Agronomy Department maintains a list of certified soil-testing laboratories in Indiana and surrounding states, http://www.agry.purdue.edu/ext/soiltest.html. Purdue Extension also has a bulletin, "Collecting Soil Samples for Testing," http://www.hort.purdue.edu/ext/HO-71.pdf.

Q. What is the best way to get rid of strawberry plants? They have not produced anything for years. We have tried pulling them out, rototilling, etc., but they keep coming back. The patch is about 6-foot x 2-foot in size.

A. It is amazing how vigorous plants can be when we want to get rid of them! A non-selective systemic herbicide such as glyphosate is generally pretty effective, especially when applied to the green foliage in late summer or early fall, as there is good translocation of the product to the roots at that time. If you want to avoid using herbicide, you could also try covering the area with sheets of plastic to heat the plants and soil and hopefully kill the strawberry plants for good. Clear plastic will allow you to monitor the progress, but black plastic can also be used. It is hard to know how long to leave the plastic in place. The hot summer weather would have been a good time to do this, but there should still be enough time yet this fall to generate sufficient heat.

Q. We have two peach trees that have so many peaches each year that the limbs break down. The peaches aren't much bigger than golf balls. I was wondering what would be a good rule of thumb as to thinning them? My husband says to let Mother Nature do it, but I think she needs help since they are so little.
 
A. You win this round! Heavy fruit loads not only result in smaller, less-quality fruit but, as you've experienced, the weight can cause the limbs to break. Mother Nature will do some thinning, but generally not enough in a good fruiting year. Most fruit trees have at least two waves of fruit drop. The first occurs shortly after bloom, resulting from lack of or incomplete pollination. The second drop occurs three to four weeks later and is usually bigger and more dramatic because the fruits have developed to a larger size, usually one-half to 1 inch in diameter. This second drop is called "June drop" (because it usually occurs in early June). Competition among the fruits for water and nutrients is thought to be the cause of June drop. Fruits that contain the fewest or weakest seeds are usually the first to drop.

Although June drop may appear to be devastating, many trees do not shed enough fruit naturally for good production of the remaining fruit. For best quality, some hand thinning is recommended before the fruit is halfway to maturity. Peaches should be thinned to about 4 to 5 inches between fruit. If you simply cannot bring yourself to remove the excess fruit, be prepared to prop up heavily loaded branches.

Q. I have been harvesting seeds from various roadside plants to grow next spring. Should I be leaving them outside to experience the climate change and so to better ensure success in growing them?

A. The many species of plants in our climate vary in their requirements for germination. Some will bear dormant seed that needs to go through some physiological maturation before they will be able to germinate. Others may have a hard seed coat that needs to be softened or abraded to permit germination.

The most common type of dormancy is overcome by moist-chilling, also called stratification. In nature, seeds are stratified as they lay in cold, moist soil over winter, but they may never actually germinate. The seeds may become buried too deep, damaged by insects and animals, or become excessively dry or wet. Gardeners can stratify seeds in a more controlled manner by placing the seeds in moist packing material, such as peat moss, vermiculite or sand. The refrigerator is just about the right temperature to provide the chilling. Although the length of the chilling period varies with the plant species, most seeds are adequately stratified for three to four months at 35-40 F.

 

 

Writer: B. Rosie Lerner
Editor: Olivia Maddox,