Update: Polyculture Groups Appear Healthier Than Monoculture Counterparts

(Zinnia elegans foliage with blight from monoculture group)

After working with severally very different species of plants, including vegetables, fruit, flowers, and other varieties, I have definitely observed some trends. In areas where one species was grouped together en mass (monoculture), the plants have been suffering from the rapid spread of disease and have suffered high numbers of insects consuming the foliage. However, plants that are more isolated from their own kind (such as ones with different species of plants in between) have fared much better. This was expected, since the physical movement of pests and diseases is made easier by proximity, and I saw this occurring with several species. The Zinnias (Zinnia elegans) that were planted in large groups have been showing signs of blight on the majority of the individual plants. However, Zinnias that are more isolated, with other plant species in between them, did not develop the blight.

Here is a photo of one of the isolated zinnias, which exhibits very healthy foliage and has no apparent signs of disease:

(Healthy isolated Zinnia plant)

On the other hand, the Zinnias from the group that were grown together showed significant signs of disease:

(Zinnias from the monoculture group suffering from Alterneria blight)

Several Zucchini (Cucurbia pepo cv zucchini) were planted in a large group, while other zucchini (also Cucurbia pepo cv zucchini) were separated by rows of French Marigold (Tagetes patula) and Marigold (Calendula officinalis). The Zucchini planted together en mass were consumed, entirely, by cucumber moth caterpillars (Diaphania indica).

(Diaphania indica larvae)

The Zucchini that were separated by rows of marigold fared slightly better -- they also had several caterpillars, but not enough to completely destroy the plant as the other group had. Interestingly enough, the zucchini plants that were surrounded by the most marigold foliage had the fewest caterpillars present.

(Adult Cucumber Moth - Diaphania indica)

Even in plant species such as Milkweed (including Asclepias curassavica, Asclepias incarnata, and Asclepias tuberosa) exhibited a sharp decline when grown in a monoculture environment, interestingly. Milkweed is considered a weed, and to many farmers, a pest. However, it is the larval food source for the Monarch butterfly, which has been in alarming decline, and its relative the Queen butterfly. When milkweed plants were grouped together, large numbers of aphids and milkweed bugs (Lygaeus kalmii) were found present, and many of the plants either perished entirely or were very stunted in their growth.

 

(Milkweed bugs and aphids on the monoculture group of A. curassavica)

Other milkweed that were located away from the main group, among different species of plants, were covered in far less aphids and rarely had milkweed beetles on them. The isolated plants were much healthier and grew much more quickly. Although Monarch larvae were present on both and consumed a portion of the leaves of either the isolated milkweeds or the group of milkweeds, the isolated milkweeds had a much faster recovery time for putting out new shoots and leaves. Individual milkweed plants located near lavender (Lavandula multifida) had almost no aphids, and there were no beetles present.
   

(A healthy isolated Tropical Milkweed plant, A. curassavica)

The only group that did not exhibit this trend was the potato and sweet potato groups and the hibiscus group (Hibiscus sabdariffa). No evidence of pest or disease was found in any of those groups, possibly because soil drainage was very good and because these plants are less disease- and pest-prone than many other crops. The sunflowers (Helianthus spp.) were overall healthy when planted in a group, and did not suffer any disease, but small portions of the leaves were consumed by moth larvae. Isolated sunflowers did not appear to have any portion of their leaves consumed.
   

(Healthy sweet potato plant - Ipomoea batatas - from monoculture group)

Organic Propogation Methods

Today I'd like to explore the different methods of growing new plants in an environmentally sustainable, organic way. There are several strategies to help grow new plants without the use of potentially carcinogenic or environmentally-unfriendly chemicals.

Seeds

Many plants can be started from seeds very simply and will sprout in ideal conditions without much interference or help. However, some seeds require extra effort in order for successful germination to occur. Some seeds, such as those from Butterfly Bush (Buddleja davidii) are very small, and because of the smaller roots that they put down when they do sprout, they are more susceptible to dehydration. Because of this, they respond well to being germinated in a covered or partially covered container, so as to retain moisture until the plant has grown larger.

(Young Royal Poinciana Plant Grown from Seed after Soaking)

Other seeds have very thick, hard outer shells, such as those of Moonflowers (Ipomoea alba) and because of this tend to rot before they soften enough for the seed to sprout. There are a couple methods that assist with this situation. First, is scarification. Scarification is any process of breaking, scratching, or altering the testa (seed coat) in order to make it permeable to water and gases. This can be done easily using fine-grain sandpaper rubbed gently over the seed coat. Another thing that can soften hard seed coats is soaking in water, typically warm water. Alternatively, another method includes using retained moisture with sterile growing medium. I have experienced a lot of success using damp paper towels or tissues tucked around the seeds in question, and then sealed in plastic with a single, small vent for air. Moisture is retained, and the seed swells. The seed coat softens, and germination is easily able to occur.

Another notable requirement for certain seeds is that of cold stratification. Several species of plants require cold temperatures  (34-41 degrees F), and often will not germinate without it -- many milkweed species (Asclepias spp.) are examples of this. This can be achieved by sealing seeds in a moist, sterile environment (such as a damp coffee filter sealed inside of a ziplock plastic bag) and keeping them between 34 and 41 degrees for approximately 30 days. Refrigerators work well for this, since they provide a relatively consistent temperature.

Cuttings

(Healthy Kiwifruit cuttings producing new foliage)

Another method of propagation includes taking cuttings from a mature plant in order to produce a new plant from the cutting. This can be done in a couple different ways. Many people use a rooting hormone (such as Rootone) to encourage roots to form, but many plants do not need this. While some cuttings may be placed directly into damp growing medium, I have observed the most success with placing cuttings in water to encourage rooting. This has worked well for Milkweed (Asclepias spp.), Butterfly Bush (Buddleja davidii), Allamanda (Dictamnus albus), Kiwifruit (Actinidia deliciosa), Hibiscus (Hibiscus rosa-sinensis), and many other various species. These were placed directly into water with leaves stripped from the lower portion of the cutting, and kept between 75-80 degrees F, and began to develop roots after a few days or longer. Once secondary roots developed, they were able to be transferred to soil successfully.
   

(Kiwifruit cutting - Actinidia deliciosa - developing roots)

Pups and Division

Many plants, such as bromeliads and irises, spread through either pups -- young plants growing from the base of the mother plant -- or by division. These are possibly the easiest plants to propagate, since they virtually do all the work themselves. For pups, simply remove the pup from the mother plant, usually by cutting between them in a downward stroke, and place the pup into soil. Keep the soil moist, and the pup will become established quickly. For plants that spread by division, the procedure is similar but the parts to be divided (the tubers, bulbs, roots, etc) are located underneath the soil.

Given that these methods have such a high rate of success, it poses the question: why are products such as Rootone, which are potentially dangerous to humans and other animals and damaging to the environment, used so popularly? Certainly many species were very successful at rooting without any hormone or chemical intervention.