I am a member of the Ecological Landscaping Association (ELA), and am part of an online discussion group that addresses various landscape issues. I wanted to share some compiled and organized information from the latest posts on irrigation:
1- Carefully Select Plants: Locally grown (with seed provenance), often native plants, placed where they will thrive. (I am not a stickler on “native” if I know the plant will thrive but not become invasive in the given site.)
2- Water Sufficiently When Planting: 5x – flood the hole twice without plant, dunk plant in water till no air bubbles rise, heel in and water, backfill and water . (I love Viterra* for keeping root hairs moist during the planting process).
3- Remineralize The Soil: Biologically test the soil and amend with proper component (bacterial and fungal components too).**
4- Retain Rainwater: Redirect all site rainfall to the landscape to create a “sponge garden” and fully hydrate the soil.
5- Hand-water: and if necessary, Point-source drip irrigation for urban settings, Low flow spray for larger settings in areas where precipitation rates are less than .75, point-source is best for keeping down weeds. And use weather-based irrigation control (rain sensors).
6- Mulch: with a natural, green woodchip mulch no more than 2″ on average in size (you want it to break down) . I love Tree Specialist’s Forest Floor Mix, which has meristem tissue in it and is a totally fabulous soil builder.
7- Maintain: with compost tea or foliar sprays for proper mineralization and to keep plants in balance.
Overall, I’ve found that in New England, if irrigation is installed at all (usually as insurance for new plantings), drip irrigation is best for potted, bare-root, and ball and burlap plantings. It should be used as needed through the first complete season to deeply water the entire root zone and wetting the soil beyond at regular but not too closely spaced intervals. After that, it can be turned on once or twice a year in August and September when rainfall is very low. Spray heads and misters do not belong in beds or anywhere containing anything but a lawn (or MAYBE a low groundcover of uniform height.) Drip is far better in terms of efficiency and performance. This is true for this type of planting and as most landscape projects use nursery stock grown elsewhere and potted, it is pretty much true. What about a meadow or other lawn-like treatment that is multi-species, multi-layered?
Meadow systems are robust – the many species and many layers can deal with wider extremes than a mono-culture lawn. I have planted a number of meadows, using seed. Every contractor that I have used, or even had a quote from, has wanted to install irrigation for these projects. All have gone naked and all are thriving. The keys are to prepare the soil by remineralizing, set the seed at the right time (early spring or before October in the fall), be prepared to over-seed in patchy areas, and be patient. Sometimes we inoculate and sometimes we add mycorrhizal fungi after planting, and I love the Universal Seed Treatment as additives. But overall, they thrive with not much help at all. There are weed seeds from the native seed bank in the soil and sometimes that first season weeding is an effort.
*Terra-Sorb is Potassium based, and may actually be better than Viterra, which is also a SAP (Super-Absorbent Polymer). Wetting agents derived from Yucca can also help.
**Mycorrhizal inoculation is another great way to ensure success. One contributor says, [I tried] “Espoma’s Bio Tone alongside Bio Tone Plus (with mycorrhizae), and Roots next to M-Roots, and Plant Health Care’s Healthy Start next to Plant Saver, and the mycorrhizal products outperformed those without.”