Eye on the Environment

Avoid weed waste: Native regrowth is best, not planted rye

by David Goldstein, PWA, IWMD and Jessica Craven Goldstein, Master Gardener, UC Cooperative Extension

The brief, hard rain two weeks ago caused calamities to the north, but local hillsides are now sprouting hopeful shoots of green. You may be tempted to help nature’s process by spreading seeds on hillsides stripped bare of vegetation, but erosion, flooding, fire danger and weed removal are the possible price to pay for planting incorrectly.

Whether on your own slopes or in the hills above local cities, lessons learned from past good-intentioned mistakes should apply. A recent email with warnings and instructions from two non-profit groups summarize these lessons.

According to the California Native Plant Society and Channel Islands Restoration, botanists, ecologists, and other professionals have found past efforts to quickly spread non-native seeds on denuded hillsides appeared successful in the short term, but caused more problems than they solved.

For example, a standard practice of the past was to plant ryegrass, which grows rapidly with little water; however, “after agencies called it a success and moved on to the next project, it would dry out…, resulting in greater fuel for fires” according to the two non-profits. Worse, these non-natives displaced perennial bunchgrasses, which send down deeper roots and are therefore more resistant to drought.

The good news is our hillsides, at least the ones left in a natural state, usually store seed banks of native grasses which respond quickly to fire. Dense, old-growth chaparral burns quickly in fires, opening space for seeds in the soil to sprout following stimulation by the fire. Even the bigger species can benefit from fire. Roots and stumps can sprout, and acorns may germinate and grow with less competition and better access to soil nutrients. Eventually, “a complex interweaving of different root types can stabilize the soil better than any artificial seeding mix that could be devised,” according to the groups.

For erosion control on more developed landscapes, these experts recommend wattles (such as straw-stuffed tubes of netting) and biodegradable mats made from material such as coconut fiber or jute. Choose a wide weave so plants can sprout through it. Aqua Flow in Ventura and Coastal Pipco in Oxnard are the two largest local farm and landscape supply stores carrying these products. Home Depot in Oxnard also has wattles ($29.95), as does Green Thumb in Ventura ($34.99), but neither has mats or landscape nets in stock as of last week.


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