Wednesday, January 23, 2008

Stevia


Question: My new year’s resolution was to loose some weight and I have heard there is an herb that can be used as a sugar substitute. Since sweets are my weakness I am looking for a natural sugar substitute. Do you know what the name of this herb is and how can I grow my own sugar substitute?

Answer: There have been few botanical discoveries quite as dramatic as the realization that the leaves of a species of herb called, Stevia rebaudiana, are intensely sweet. Stevia plants are perennial plants native to Paraguay that include over 150 different species. However, this particular species is an anomaly, since none of the other species in this North and South American genus produce these sweet compounds at high concentrations. Stevia sometimes called “sweet leaf or candyleaf” is considered by the U.S. Food and Drug Administration to be an unapproved food additive. It is approved by the FDA only as a dietary supplement. There is conflicting research on the safety of this herb and you should research carefully before using any herbal product.
Because they are commercially unprofitable, relatively few highly sweet plant components have been developed as sugar substitutes. However, due to the interest in natural products, the discovery that this stevia plant has naturally occurring sweetness has attracted great interest. Stevia and stevioside, an extract of stevia, have a menthol-like, bitter aftertaste that limits their usefulness. However, they have been used for years as sweeteners in South America, Asia, Japan, China and some European countries.
For many centuries native Paraguayans have used stevia as a sweetener in herbal and medicinal teas. As mentioned, stevia cannot be sold and advertised as a sweetener but it is available as stevioside extract and can be purchased at most health food stores. The first thing to remember is that stevia is sweet but not exactly like sugar. All this sweetness comes from the leaves of a rather homely little plant that at maturity can be up to 18 inches tall and as wide. It’s a perennial herb that won’t tolerate freezing temperatures. Therefore, grow it as a houseplant or treat it as a tender annual that’s set out after all danger of frost is past. Bear in mind that temperatures can affect the sweetness. The stevia leaves will be sweeter as the temperatures increase throughout the summer.
Stevia is can be grown from seed, but is more easily rooted or it may be purchased as a small plant in the herb or perennial section of the garden center. Your small plants will start slow, much like a pepper plant or okra which requires hot weather to grow well. They need a good rich soil, full sun, warm air, and just enough water to keep the growing medium evenly moist. They’ll be quick to drown if you over water and equally quick to die if you let the soil dry out completely. If you are more interested in the sweet leaves you should remove the small white flowers that appear in summer. They are heavy users of nutrients and should be fertilized regularly or use a slow release fertilizer at planting. They may occasionally be attacked by aphids, mealy bugs, and spider mites, so keep an eye peeled. If you catch the pest early a strong stream of water may be all that is needed or use a little insecticidal soap as directed on the label.
Use stevia leaves fresh or dry them for storage by placing them in single layers between paper towels set in a warm place for a week or so or dry them in a dehydrator. Then use a spice grinder to reduce them to powder. It may not solve your sweet tooth problem but you are bound to burn a few calories while working in the garden.


Note: See this publication from which much of this information was derived. Thanks to Georgia Jones, Extension Food Specialist at the University of Nebraska.

Monday, January 7, 2008

Drip Irrigation


Question: I want to install a landscape at my new home but am very worried about the water shortage. What tips can you give to increase my chance of success?

Answer: The first suggestion would be to plant as soon as possible. In our area we can plant woody plants all winter if the ground is not frozen. The plant roots will start to grow and establish before the plant top growth occurs and before the stress of a hot summer.

Second, I would encourage you to consider using a low volume irrigation system. Low volume irrigation unlike sprinklers puts the water in a small area near the plant. Sprinklers are very wasteful because they water the entire surface area and much of the water either runs off or evaporates. Low volume methods work by placing emitters in a flexible tube near the base of newly planted trees and shrubs. (picture at right is from the University of Texas publication on "Low Volume Irrigation")

The primary design goal of a low volume system is to apply water to a uniform soil depth. Water is delivered at or below the surface of the planted area exactly where it is needed. For new landscapes the emitter should be placed directly over the edge of the root ball of the newly installed plants. This will keep the root ball moist while encouraging new roots to develop in the native soil. For larger plants you may need two or more emitters to insure the root ball maintains adequate moisture.

These systems are not difficult to install and remind me of playing with tinker toys as a kid. The most critical part of installation is making sure you reduce the pressure before the water enters the drip tubes and provide a screen filter in-line to avoid stopping up the small holes in the emitters. It is very important to periodically check the emitters to make sure they do not get stopped up. Unlike sprinklers which are highly visible you can’t really tell if emitters are working unless you inspect them while they are operating.

I have often been asked why can’t I just punch or drill a small hole in a water line near the plant rather than buying emitters. The answer is simple. These small holes would not distribute the water evenly, the water would come out too fast, and the hole would get larger over time. Emitters are designed to put out very slowly at rates from ½ to up to 2 gallons per hour. If your soil is a very heavy clay soil you would want a very low rate emitter and if it is sandy you could use the higher rates. If you use a high rate emitter on a heavy or hard soil the water will pool on the surface and run off the target area.

I know many municipalities tell their customers to do hand watering only during times of water shortages but low volume drip irrigation is even more water conserving then hand watering. Generally speaking when people do hand watering on new plants they water a larger area than necessary, water is applied too quickly causing runoff, and some water evaporates before reaching the ground. Also, who’s going to know if the water is on if it is below the surface. I am not encouraging wasteful use of water but I believe this is even more water conserving than hand watering and I would not feel the least bit guilty for using this method in lieu of hand watering. Just make sure you are using a timer so that the system only runs a prescribed amount of time. I made the mistake of leaving mine running without a timer several years ago and floated my plants out of the ground after a couple days. To learn more you may watch a short training video for gardeners at Texas Earth Kind web site and choose the "Low Volume Irrigation" tab.