Book Reviews

How to Grow Fresh Air

50 Houseplants that Purify Your Home or Office

Dr. B.C. Wolverton, 1996

Penguin Books, USA Inc.


by Peter Szilagyi


Not only do houseplants look wonderful and have a soothing psychological effect upon us, but they also purify the air that we breathe. They absorb harmful man-made toxins during their respiration, photosynthesis cycle, and emit breathable, life sustaining oxygen.

Key to this discovery were the studies, which NASA conducted, related to the possible problems that astronauts would have in the sealed environment of the Skylab missions.

A study by NASA in 1980 indicated that houseplants removed harmful VOCs (Volatile Organic Chemicals) in a sealed life support system.

A follow-up study, resulted in a 1989 report which evaluated the ability of 12 common houseplants to remove formaldehyde, benzene and trichloroethylene in sealed chambers.

As with any new discovery, it produced a number vocal skeptics, who stated that these sealed- chamber studies could not be extrapolated into the real world. In order to address these aforementioned complaints and concerns, NASA developed and built a chamber known as the ‘Biohome’, which was also able to study whether these plants could possibly mitigate such earth problems as ‘sick building’ syndrome and indoor pollution ( in homes ).

This study consisted of 15 different houseplants with a fan assisted air circulation system. What this new study revealed was extraordinary!

A sampling of the air within the chamber indicated that after several days, the amount of VOCs was substantially reduced.

Formaldehyde and VOCs are ‘off gassed’ (released into the atmosphere) by many man-made products found in residential, institutional, educational, and commercial buildings. They are found in paint, floor and wall coverings, commercial adhesives, carpet backing, plywood, particle board, paneling, plastic laminate, and cigarette smoke, etc.

In 1990, a study cosponsored by the ‘Plants for Clean Air Council’, a non-profit organization and ‘Wolverton Environmental Services, Inc.’ expanded the earlier NASA study. Fifty houseplants were tested as to their ability to remove various toxic gases from sealed chambers. The results of that study are documented and illustrated in this book. The photographs of each of the 50 plants are excellent.

Not only does the book rate an individual plant’s ability to remove various toxins, but it provides such additional and useful information as: its ‘ease of growth and maintenance’, its ‘resistance to insect infestation’, and its ‘transpiration rate’.

Also indicated for every plant is its origin and its light requirements, the pests and problems it may have and tips about its care and finally the planting media that it prefers.

This informative book is a must read for those, who are thinking about acquiring houseplant for the first time or adding to and varying their existing collections.


CITRUS: Complete Guide to Selecting & Growing More Than 100 Varieties
For California   Arizona   Texas   The Gulf Coast   Florida
By Lance Walheim, Ironwood Press, 1996. $19.95

by Joan N. Nestor-Roses


On a sweltering hot Sunday I finally get a few hours to read/review this book. It’s a very good, comprehensive, beautifully photographed paperback, and is highly recommended.

With our cold winter climate, we need to know about container growing appropriate stock and indeed there are all the answers we need to know.

Microclimates get lots of attention. “Cold air moves like water, flowing down hillsides, settling in low spots, damming up behind buildings and fences.” “For example, a fenced-in yard tends to trap more cold air than one that is open. Simply opening a few gates may provide the drainage so the area remains a few degrees warmer on a cold night.”

The only serious disagreement I have is on p. 25. There the author recommends you coat the inside of wooden containers with asphalt roof patch as waterproofing. PLEASE DON’T DO THAT!!! You don’t want to taint your foods with petrochemicals.

“The frequent watering required by citrus growing in containers causes nutrients to be leached from the soil. Plants must be fertilized regularly. Feed plants once or twice a month using a liquid, high-nitrogen fertilizer that includes the micronutrients zinc, iron, and manganese.” 

To ease the stress on the plant, Mr. Walheim recommends a 3- to 4-week transition time bringing the citrus out in the Spring and then back in again in the Fall.

Even if you are not going to grow citrus, the book contains good information about citrus in general for those of us that like to EAT them.

“The proper way to pick citrus fruit is to either cut it with pruning shears or grasp it with your hand and give it a quick snapping motion. The small button at the end of the branch stem should stay attached to the fruit. If it is torn away, the fruit is more subject to decay organisms and will not store as long.” That’s a good thing for consumers to look for when purchasing too.

If you squeeze your own juice, know that Navel orange juice and Blood orange juice should be consumed promptly as keeping it, even a few hours, will turn it bitter. Use “common” oranges without navels for longer term storage/freezing.

Colors of the outside and inside can vary depending on where on the tree it’s growing and how long it’s left on the tree. Some varieties can remain on for extended periods without harm.

“Bees are the most common pollinators of citrus.” What will that mean to our food crops with the decline of those precious insects??? What will our society do if it turns out to be X-Ray Cell phone towers that are disrupting their life cycle and leading to the bees’ rapid decline???

Meyer lemon and Improved Meyer (Virus Free) “is probably a hybrid between a lemon and a mandarin or a lemon and an orange.” “Meyer lemons are much hardier than true lemons, withstanding temperatures into the mid 20F.” “Meyer is one of the most popular home-garden citrus.” “Grapefruit has the highest heat requirement among citrus”.

If you can handle the taste, kumquat fruit are small and are eaten whole, rind and all. They are also candied and made into preserves and sauces. The third and most important aspect of kumquats is that are cold-hardy plants, able to withstand temperatures below 20F with little damage to the foliage. Even though the small fruit is fairly cold sensitive, the trees can be grown in areas that are too cold for most other kinds of citrus.”

“Citrangequats are hybrids between kumquats and citranges (itself a hybrid between trifoliate orange and sweet orange). They are hardy plants, even more so than kumquats, surviving to 0F.” Wow, think of the experimenting we could do with warm microclimates!

The “Etrog citron (primarily a novelty, who has heard of it?) remains an important part of the Jewish Feast of the Tabernacle.”

Be wary, “Because the French word for lemon is citron, the citron is often confused with lemons. Many imported or exported lemons and commercial lemon by-products such as marmalade are labeled as containing citron, even though they actually contain lemons.”

There are endless limiting conditions and variables but the plants do like to get a little dry before they are watered thoroughly again. GOOD DRAINAGE is important and don’t get the trunk wet!

“Scales are probably the most troublesome citrus pest.”



Now, if you grow them or buy them here are two recipes from the book to help keep you cool this hot summer. Enjoy them while you read about citrus!!!  And don’t forget to stop and smell the roses.

Basic Recipe for Lemonade
Adjust for your own taste

3 cups fresh lemon juice

3 cups water

1 cup sugar

ice

Add 1 teaspoon of lemon zest (rind only – not the white) for extra flavor


Quick Meyer Lemon Sorbet


Pour one envelope of unflavored gelatin, ¾ cup sugar and 1 ½ cups water into a 2 quart saucepan. Mix ingredients well. Bring to a boil on high heat, stirring frequently. Reduce heat and simmer for 5 minutes. Add 1 ½ cups of Meyer Lemon Juice and 2 tablespoons grated fresh Meyer lemon peel. Pour into a 10 inch square (or similar size) metal pan. Freeze until hard – about 3 hours. Remove from the freezer. Let stand at room temperature until it can be broken into large pieces. Place the pieces in a blender or food processor and whirl until smooth and frothy. Spoon into dessert dishes and serve immediately. Serves 4 to 6.