I can’t overstate the importance of mulching annuals with straw. A few years ago, while doing an internship on a farm in upstate New York, were the focus of production was on heirloom tomatoes, the emphasis on straw mulch was loud and clear. It’s a good idea to mulch most vegetables, especially long term crops like kale, carrots and eggplant.
For one thing, a basic rule in gardening or farming is to avoid bare soil. Bare soil tends to erode, compact and loose structure, whereas soil either covered by a crop or mulch will have improved structure and increased organic matter. With certain crops, where plants are spaced wide apart, mulching helps to shade and protect the soil around each plant. It keeps soil from splashing up onto plant stems and leaves, which helps to prevent soil born pests, an issue with tomatoes and other crops that are susceptible to fungus. It also helps retain moisture in the soil around plants, making irrigation more efficient. It suppressed weeds, which are usually more of an issue around long term crops.
Not all mulch is created equal though. Here in Miami it is very popular to use chipped wood as mulch and that’s mostly due to the fact that it is abundant and free. It is very easy to get a free dump truck of freshly chipped wood, palms and shrubs delivered to a garden site. Wood mulch is great for trees and perennials; for one thing it promotes fungal environments, which are natural and beneficial for trees and perennials. It also breaks down slowly, releasing nutrients over a long period of time, which is more compatible to the slow and long term growth of trees and perennials. On the other hand, straw comes from annual plants; it doesn’t get woody and breaks down fast, releasing nutrients at a rate compatible to the short life span of annual plants. Straw also promotes bacterial environments which are beneficial to annuals.
Straw is a rare treasure around here, not only because it is urban, but because it is tropical. No wheat, rye or oat fields around here. Bales of straw come down to South Florida by truck, primarily for the horse industry and it’s price tag reflects it’s journey. A bale of straw can go anywhere from $7 to $10 each, which adds up if you are mulching a large garden, let alone a farm scale operation.
My first year growing food in Miami I noticed an important coincidence between planting time and Halloween. Churches, pumpkin patches, parades and parties all use bales of straw to create a “Fall setting”. After the holiday they have no use for the bales, in fact, they become a burden because they are bulky, heavy and “useless”. That’s where I come in with my truck and trailer. It’s a win win and I’ve been enjoying the symbiotic relationship ever since.