July 16, 2021 - By Brian David (U.C. Master Gardener, Mariposa) - Bare ground is naturally rare. The earth covers its surface with plants. Plowed fields need to be quickly seeded or nature will seed her exposed surfaces, (usually with seeds growing into weeds). Looking at wooded areas you’ll see layers of plant matter transforming into soil, providing the soil a blanket in the process.
Mulching accelerates the forest floor process in our gardens. Three- to sixteen-inch-deep mulch will distribute moisture, reduce soil evaporation by 35%, regulate temperature changes, reduce soil compaction, and increase soil aeration and water holding capacity. Invigorated soils sustain healthy crops.
Wood chips, straw, almond hauls, rice hauls, and shredded dried leaves make good mulch. Use straw, not hay, as hay may harbor seeds that will come up in the garden unless the hay bale is first dampened and sprouted out. Alfalfa hay is an exception and makes a good mulch but is expensive. Rock can be an attractive mulch but should have a ground cloth between the aggregate and soil.
Are there any down sides to using mulch in your garden? A few. Some of our California native plants may not adapt to a heavy mulch. Squash beetles overwinter in bark and dried plants on the soil’s surface. Mulch may hold too much water inviting snails and 
sow bugs. This often happens with the thin threads in lawn clippings that mesh together. If mulch is not well dried it can transfer whatever disease the mulched plant had, this often accompanies using ground tree roots for mulch.
Mulches that cover the crown or tree trunk can harm a tree. Mulch touching the stem of a plant may cause plant damage. So, keep a safe distance around a tree trunk or plant stem.
Dry flammable materials like shredded bark, pine needles, or wood chips near a structure can keep smoldering embers alive for days. So, dry plant mulches should be several yards from a structure. Overall, mulching is a good thing.
One productive method of mulching includes: (1) covering you planting area with moist paper or cardboard. Newspaper should not have colored images or a shiny gloss. Paper stack about four sheets thick will cut off weed growth. Cardboard should be thin, not shiny with tape removed, (2) layering mulch onto of the paper (3) planting seedlings are into openings cut into the paper, (4) seeding a row etched in the soil below the mulch. Cover seedlings with moist soil and keep them damp until you see emerging seedlings between your mulch walls.
Conserve water this summer; become a mulcher.
For assistance, contact our Helpline at (209) 966-7078 or at mgmariposa@ucdavis.edu. We are currently unable to take samples or meet with you in person but welcome pictures.
Updated: The U.C. Master Gardener Helpline is staffed; Tuesdays from 9:00 A.M. - 12:00 P.M. and Thursdays from 2:00 P.M. - 5:00 P.M.
Clients may bring samples to the Agricultural Extension Office located at the Mariposa Fairgrounds, but the Master Gardener office is not open to the public. We will not be doing home visits this year due to UCANR restrictions.
Serving Mariposa County, including Greeley Hill, Coulterville and Lake Don Pedro
Please contact the helpline, or leave a message by phone at: (209) 966-7078
By email (send photos and questions for researched answers) to: mgmariposa@ucdavis.edu
For further gardening information and event announcements, please visit: UCMG website: http://cemariposa.ucanr.edu/Master_Gardener
Follow us on Facebook at: https://www.facebook.com/mariposamastergardeners
Master Gardener Office Location:
UC Cooperative Extension Office,
5009 Fairgrounds Road
Mariposa, CA 95338
Phone: (209) 966-2417
Email: mgmariposa@ucdavis.edu
Website: http://cemariposa.ucanr.edu/Master_Gardener
Visit the YouTube channel at UCCE Mariposa.
