The jury is still out. I ignore commercial opinions, like people who manufacture or sell the stuff, and concentrate on university trials. Here's a sample: Cornell on Red Mulch: "There has been much discussion recently about using specific colored mulches on different vegetable crops to achieve earlier or higher yields. When used by a roadside stand, these mulches can certainly draw quite a bit of attention! However, the research results from studies examining red mulch under tomatoes is very conflicting- in some cases, a yield benefit was observed, in others, no benefit. Different tomato varieties also appear to respond differently to the red mulch. The scientific theory behind using red mulch is sound- a specific pigment system in plants (phytochrome) responds to specific red wavelengths of light. If we enhance those wavelengths in the plant canopy, we should be able to change plant growth. The effect of red mulch, like that of IRT (Infra-red Transmitting) mulches, depends on sunlight levels. Part of the variation in results in the Northeast may be related to the differing levels of total sunlight and average air temperatures. Red mulch can act like an IRT much and will increase soil temperatures compared to black mulch. Some of the benefit to tomatoes is suspected to be due to this temperature effect. If used for the early plantings, some yield benefit may be observed with red mulch due to soil warming. When used with main season plantings, the effects of red mulch may be more variable. Red mulch, however, is more expense than IRT, requiring careful consideration of crops and markets you are targeting. Start small if you are considering experimenting with these colored mulches. There have been problems with both the product quality (breaks down early, may need more UV stabilization, prone to tearing) and visible light transmission (poor weed control under many of these). Research continues on the use of red and other colored mulches around the region, and hopefully, we will soon have some field scale trials and economic analysis of these products. " Montana State University: "I headed a study that for two years examined the uses of colored plastic mulches on tomatoes and peppers, two high-priced crops that are sometimes difficult to ripen sufficiently in areas with cool summer nights and short growing seasons. Here's what we did, and here's what we found out. We planted tomatoes and peppers in the 1999 and 2000 seasons at Bozeman. Some we maintained in bare plots and some we kept mulched with either red, silver, or black plastic. Let's talk about peppers first. In 1999 the various treatments had no effect upon the total number of fruit each plant bore, though in 2000, plants mulched with either silver or red mulch bore more fruit than plants in the other treatments. In 1999, plants mulched with red and silver plastic set more fruit earlier than those on the other treatments. In 2000, plants on red mulch had the greatest early fruit set. In both years, plants mulched with either red or silver plastic set more fruit earlier than those on the other treatments. So it looks like red and silver plastic mulch speeds up fruit ripening in sweet peppers. Silver plastic mulch also significantly increases the number of roots in sweet pepper plants, potentially allowing them to grow bigger and produce more fruit. We also grew tomato plants on bare soil or in plots mulched with either silver, red, or the traditional black plastic mulches. In 1999, plants grown on silver or red mulches produced the greatest number of fruit, while in 2000, those grown on silver mulch produced the greatest number. On the other hand, plants in both years grown on silver and red mulches produced the greatest early fruit set and the greatest number of ripe fruit. To make sense of all this, red and silver plastic mulches produced the greatest number of ripe fruit and early set of any of the treatments. This is important in colder areas of our region where hot summer days are followed by cool nights and where the entire growing season is marginal for these crops. And the experiments are important in showing that black plastic mulch may not be the best one to use. In fact, in our study, black plastic was fairly comparable to no mulch at all regarding fruit set and ripening. Now, as with all research, this experiment must be repeated in many areas of our region over many years in order for us to flesh out the entire effect of colored plastic mulches on crop production. But we can now say, at least, that silver and red mulches speed ripening in tomatoes and peppers under Bozeman conditions. Do your own studies. Try red and silver plastic mulches in your garden on these and other crops and let me know what happens. " University of Vermont: "Studies of red mulch have not shown consistent results. Red mulch sometimes increases yield of tomatoes, but not always. Different tomato varieties also appear to respond differently to the red mulch. The effect of red mulch, like that of IRT, depends on sunlight levels, so the variation results in studies may be due to different light conditions, as well as different temperature conditions. Red mulch does tend to increase soil temperatures much like an IRT, so in early plantings it is likely to promote earlier yields. When used with main season plantings, the effects of red mulch may be more variable." UCONN (& Penn State) "Red mulches were the first really new color to be investigated, other than the ones mentioned above and have started to be used commercially. There have been alot of trials on tomatoes, some that have shown a benefit either of improved yields or enhanced ripening and quality of the fruit. In other trials, there has not been a response. There is also some indication from different trials that red mulch may also be reducing the severity of early blight on tomatoes. This is indeed an interesting finding that may have some real benefit. Red plastic mulch has also been shown to increase yields in zucchini and in honeydews and muskmelons. In a study in New Hampshire, researchers found that differences in reflectivity among a red, black and red on black mulch were minimal at 16 inches above the mulch surface and on the shaded side of the row. They speculate that for red mulch reflectivity to have a more sustained and more consistent effect on biomass accumulation and yield in tomato, the rows may need to be oriented in a North-South direction. A summary of two years research at Penn State on crop response to red, brown IRT, green IRT, black, silver, white, blue (light and dark) and yellow color mulch is presented below: Tomatoes. No significant difference in the yield of marketable tomato fruit (cv. Sunbeam) from clear, yellow, black, silver, red or brown IRT mulch. Peppers. No significant difference in yield of marketable peppers fruit (cv. Enterprise) from clear, yellow, black, silver, red and brown IRT mulch. Fruit grown on yellow produced the smallest fruit. Silver, red and clear mulch appeared to hasten maturity of the peppers harvested compared to the black or yellow treatments. In 1998, plants grown on silver mulch significantly produced more marketable pepper (cv. Marengo) compared to those grown on white mulch. There were no significant differences in marketable pepper among the other colors (green and brown IRT, black, red, yellow and blue). Pepper plants grown on either silver or green IRT mulch produced larger fruit compared to brown IRT, black, red, white, yellow or blue mulches. Highest soil temperature, taken on August 3, 1998, was recorded under green IRT mulch 103 o F and coolest under white (89o F). Muskmelons. Plants (cv. Cordele) grown on green IRT, blue, red, silver mulch produced significantly more fruit (total yield) than plants grown on white mulch. In addition, plants grown on green IRT or blue mulch produced significantly more fruit compared to plants grown on black mulch. Larger fruit was harvested from plants grown on brown IRT mulch and the smallest from plants grown on black mulch. Zucchini and honeydew. Blue-colored mulch improved yields of zucchini, honeydew. This light reflectivity can affect not only crop growth but also insect response to the plants grown on the mulch. Examples are yellow, red, and blue mulches, which increased green peach aphid populations, especially the yellow color, which attracted increased numbers of striped and spotted cucumber beetles. There may exist the potential to use this information in developing an insect management program where a row of yellow mulch is laid in the field after a certain number of rows of whatever mulch is being used for the crop. It would be considered a trap row. In a trial in Pennsylvania, the highest yield of peppers was from yellow mulch. Since, it has been proven that insects are attracted to this color, a grower has to really be on top of their scouting for insects. Yellow has long been used in greenhouses and now in high tunnels to monitor insects. Similar to a white color mulch mentioned previously, the degree of opacity of these newer colored mulches may require a herbicide or fumigant to be used to prevent weed growth. Some of these colored mulches, for example blue and red, can have a dramatic impact on the soil temperatures, raising soil temperatures to 167o and 168o F, respectively, at the 2-inch depth when the ambient air temperature was 104 o F (my research in Kansas). Summary. There are still many aspects of colors that we really do not understand. We know that we can build a mulch to specific spectral parameters or wavelengths and that will determine the color. The color of the mulch will influence the soil temperature, the surface temperature of the mulch and the light reflected by into the plant canopy. We know the blue color in the 440-495nm wavelength band will cause a plant response- phototropism, photosynthesis; while red color in the 625-800nm wavelength band will influence photosynthesis, seed germination, seedling/vegetative growth, and anthocyanin synthesis. Another impact on the effectiveness of a color is if the mulch is applied to a raised bed or is laid flat on the ground. This can cause a difference in the impact a mulch can have on the soil and plant microenvironment. The last consideration is the difference in color retention, film appearance, and film longevity of mulches currently on the market. This is the critical question of what really is a red, blue or yellow mulch and how best do we define it. To anyone who has ever look at a color additive chart, the problem is readily apparent. A lot more research still needs to be done on the effect different colors have on the microclimate, vegetable crop growth, yields and earliness."

Periwinkle (Vinca minor) was the first thing that popped into my mind, too, but I have to say that its flowers are usually blue, not purple. It's a staple of my parents' house near Philadelphia because my mother just loves it. I think it's pretty, too, although I don't grow it where I live now. I understand it has the potential to be invasive, although in my experience it's usually mostly "persistent", rather than "invasive" (unlike English ivy, or Lamium, or Bishop's weed).

Lucille, almost all of my plants are indeterminate. I let them grow up to the top of the tower, 54 inches or so, then grow back down to the ground, then wherever they want to after that. I plant 1 row of 4 plants, 2 feet apart, then another row of 4 plants 2 feet apart, and each plant is also 2 feet from the other row. Essentially it is 2 double rows on a 2 x 8 grid. Then I go 4 feet on each side of that and plant another 2 rows past it and another 2 rows on each side, etc. At least that is the MINIMUM spacing I will use. I have cut my yearly tomato plants from about 160 to around 120 and I often space them 3 feet apart, now, but it is still too close. 2 X 2 gets the job done. 3 X 3 is better, but I am not your typical tomato gardener. I grow for fun, not production. I also want to emphasize that. I AM NOT looking for maximum production per plant. I plant so many plants because I am BREEDING them, and all I need is enough tomatoes from the INTERESTING plants that I can save seeds. I eat as much as I can of the rest, since I love tomatoes, and I give them away to whoever wants to come pick ALL that they want, as often as they want, but mostly I watch the rest just fall on the ground and rot. I also grow the pumpkins and squash for fun, mostly. My wife likes to cook a few in her beans and other dishes. Then in the Fall I let the kids, grand kids, nieces, nephews and whoever come haul off all the pumpkins they want. Most of the rest end up in a pile on my porch for Halloween. I generally get many dozens of pumpkins and squashes of all different sizes and colors. Even after all of the above, some of them often remain in the garden and rot and a lot of the pumpkins I grow every year will come from volunteers from the seeds left by these remaining pumpkins. But I do make sure to always plant seeds from some of the more interesting varieties.

Besides periwinkle (vinca), there's ivy (no flowers but there are some varieties with white marbling), lamium (dead nettle)(pink, white, purple or yellow flower depending on variety and some have a silver stripe on the leaves), snow-in-summer (bishop's weed), pachysandra, goldenstar (limited season bloom), or Geranium sanguineum Tiny Monster or Geranium Cantabrigiense Biokovo/Cambridge/Karmina/St. Ola (these are often lemony scented, bloom well all summer, and the leaves turn reddish in fall, and the plants stay low and do not flop and naturalize well... I use Geranium Cantabrigiense Karmina as a ground cover around my roses because I hate weeding around thorns). There's also chameleon plant and ajuga if you don't mind something invasive. Ajuga will easily get in the lawn despite any efforts to stop it. I think all of these are pretty low maintenance.