Q. How do I maximize growth and vigor of all the plants in my High-Sierra, mountain garden? This was a recent question… wow. there is really no short answer. I might say: “Plant very well, fertilize like crazy, mulch like crazy, water like crazy and prune like crazy” and that would be accurate but few would get the implications… here goes.
There are as many different types of gardens as there are ecosystems and personalities of gardeners. High Sierra gardens tend to fall into just a few MAIN categories (with infinite variations therein). 1). To the east, the high-desert, sage-scrub ecosystem gardens are sparse with an abundance of silvery, spiky or succulent foliage, accent boulders, and rocky mulch. 2). Rock-gardens highlight the beauty and rugged nature of high elevation species that nestle in crevices and hugging the boulders. 3). Our abundance of pine, fir, and cedar create ideal conditions for lush woodland / forest gardens. 4). Many of us also have some sort of vegetable and / or herb garden in the ground, raised-bed or pot.
The important requirements of any vigorous landscape or garden in Truckee / Tahoe begins below ground. Those plants for the high-desert east-side and the rock-biting alpines tend to need very little but they also grow very, very, slowly. So, for MOST gardens in Tahoe and Truckee, the following are essentials. The most common Sierra home landscapes strive for more greenery, flowers, groundcovers, maybe a little lawn, shade and screening.
For fuller greener landscapes that grow best and fill-in quickly here is my advice: plant well in wide holes with ample mature compost (it is vital but it breaks-down quickly); fertilize very well at planting and at least once a year after that; water regularly, deeply, and broadly as the root-system expands out ; AND mulch, very, very, very, well on top of the soil with ground-up wood (“double-run” native wood chips) or bark that insulates and shades the soil and provides a long-term source of more and more humus (mature compost), working into the soil, as the mulch breaks-down.
Ok, I should back-up… I’ve seen many dozens of soil analyses for Truckee and Tahoe soils over the years and with one or two exceptions, they all show, roughly, the same results. For all intents and purposes, we have what anyone else would consider “mineral sub-soil” as our “topsoil”. We have ~0.0001% organic matter, ~0.0001% nitrogen (N), moderate but ample phosphorous and potassium, plentiful micronutrients (in our glacial rock-dust) with the exception of slight deficiencies in Ca (calcium) and S (sulfur). The up-side is that when you incorporate mature compost into our “dirt” and add a little organic nitrogen, it turns into pretty good soil.
Soil organic matter is ideally 5-7% of a healthy, productive soil. One Michigan study, for example, demonstrated crop-yield increases of nearly 12% for every 1% increase in soil organic matter. Nitrogen is the number one element, brought in through the roots (mostly), that plants need. Available nitrogen (usually NH4 and NO3) comes from, animal urine, soil microorganisms, from decaying organic material and from lightening through the air (rain can provide N directly through the foliage). Nearly 80% of the air we breathe is nitrogen gas (N2) but plants cannot use it in that form. Carbon is arguably most important single element used in and by plants but without nitrogen, plants cannot make chlorophyll, and without chlorophyll, plants cannot photosynthesize. i.e. collect CO2 from air and use sunlight to create stored chemical energy while releasing O2 (thank you) back into the atmosphere.
Using organic fertilizers adds soil organic matter AND a little available nitrogen, at the same time, to our lacking and hungry soils. Maintaining a 5-6” layer of ground-up wood mulch over the soil provides a lasting source of organic matter for months (or years), while protecting the soil surface (and the very shallow roots) from drying, from freezing and thawing, and from wind and rain erosion. A good rule of thumb for organic mulch: You should be able to dig-down through your mulch, a week after irrigating and still find moist soil. If the mulch stays moist at the soil surface, the microorganisms remain actively digesting the wood. Less than 4-5” of ground-up wood mulch will not do that. Much more than 6” of mulch may begin to bury plants. Pine needles can be composted and then used as mulch but fresh pine needles allow too much wind and dry air into it so it dries quickly and breaks-down slowly. Do NOT bury the trunks, branches or stems of your woody plants with mulch; the root-collar / crown should always be visible. Root tissue tolerates dark and wet conditions; trunk and stem tissue, on most woody plants, does not. It is also very important to understand that our fine silty native mineral soils will wick water away from your plants. Say, for example, you plant a tree well and mulch just a 3’ diameter circle. The sun shines and the dry winds blow across the bare soil 4 and 10 feet away, desiccating those soils directly adjacent to your tree. When you irrigate your little 3’ diameter tree and plot, that talcum-like dust next-door is aggressively wicking away the water you just added. If, however, you effectively mulch a 10-20’ diameter area around your tree, you’ll be able to get by using about half as much water while your tree, never having to go through drought-drown cycles, will grow, potentially, twice as fast, and he root system will more easily expand.
As perennials and shrubs grow, the bare earth beneath them becomes shaded and protected. Plants do create their own mulch so it is not essential to add wood-ships under every perennial, groundcover or dense shrub. That said, I mulch even the tiny grass plants of my lawn every year with a fine compost and use organic fertilizer in fall and summer.
What we do: In late fall, November, we use Biosol on all our landscapes, at home and here at the nursery. We spread it liberally throughout the trees, shrubs, groundcovers, meadows and we use some in the potted plants that we bring in to overwinter. Whenever we plant, we use a combination of Biosol and some G&B (bioactive) fertilizer (usually Lawn 8-1-1 which is pelletized chicken feather and manure). Adding an organic fertilizer with living, beneficial bacteria and fungi increases the natural release of the nutrients in Biosol while improving the soil in myriad ways. We also use mature, finished composts like Gromulch or Amend with low C:N ratios and ample humus in our planting holes. We’ll also use chicken manure and when available, aged horse manure (big fan).
In spring, we top dress lawns and groundcovers with Topper, a fine textured compost that works its way down to the soil surface and improves the health and vigor of any groundcovers all summer long (we occasionally use topper in fall on areas where the soil appears to be getting “tired” and the groundcovers are growing less vigorously and any time we aerate a lawn). In early summer, we use the G&B Lawn food on lawns, ornamental grasses, ground covers, vines, perennials, shrubs and all trees. An 18lb bag covers ~2000 sq.ft. of lawn and more than that of general landscape (I spread it by hand like chicken feed wherever I desire a little more growth… it is very hard to over-do it). On acid-loving blueberries, conifers, roses, mountain-ash and dogwoods, we also use cottonseed meal, an age-old favorite of specialty rose growers, and MaxSea acid fertilizer, a powder that mixes in water, on those same plants about mid-summer. We add a little oyster shell lime, a long-lasting calcium source, every couple of years, to Paeonia, Dianthus, Delphinium and Syringa. It is also great to add lime, every year or two, over calcium loving bluegrass and clover lawns.
We generally water 3 times a week on lawns and new plantings. Water deeply enough to soak the soil at least 8” on lawns and perennials and to over 12” for trees and shrubs. A reasonable rule of thumb, if mulch has been used, is to apply a little more than the gallon size of the original pot in H2O every week, i.e. a #15 (“15 gallon”) tree would get 3 x 5g waterings each week, over the first season of planting. Drip irrigation is the standard for conserving water but it is important to be aware that roots grow out, wide and far and you must add and move the drip emitters out each year as the trees grow. It is disappointing to visit a landscape where drip emitters are wrapped around the trunks of trees planted by someone 5 years earlier; those trees should have roots out to as wide as the tree is tall by then with very few remaining right at the trunk. Mulching, again, is one of the simplest and cheapest methods of improving root growth and thus, increasing top growth and vigor while reducing water needs at the same time. If the mulch is thick enough, it will continually provide a source of organic matter as the woody mulch is digested by microorganisms. In case you were wondering, most of our natural organic decomposition (i.e. out in the woods) in the High Sierras occurs in winter, under the snow (surprise?), by very active fungi. Replenishing your mulch in fall is always a good idea.
I was trying to be brief and concise with this and then every thought has dozens of connections that may need explanations. I neglected to mention pruning: Pruning should be done in late winter / early spring and in summer, not fall. Cuts made in fall cannot seal over until spring. Imagine ripping a hole in your arm in October and having to think “Dang! Now this won’t heal until May.” Additionally, as they enter dormancy up top, deciduous trees and shrubs store nutrients and energy in their stems, branches and trunks, so pruning in fall is like stealing a squirrel’s nuts. Many (if not all) shrubs evolved side-by-side with the herbivores that eat them and many shrubs simple never look their best, nor grow quickly, unless they are browsed (or hedged, a natural occurrence). The best time for “heading-back-cuts” (hedging) is spring through summer (when it would naturally occur by way of elk, moose, caribou, reindeer, bison,…). Unfortunately our Mule Deer are lousy browsers. Their role in the ecosystem, like voles, is simply to convert ANY vegetation into meat for large predators. And since large predators are currently mostly absent from our ecosystems, there are far too many deer.