With ecological consciousness forever on the rise, people have become more & more interested in the potential of low water, low maintenance plant selections to serve active duty in the urban landscape. Typically, at the end of winter, the inner-gardeners come out of the cask and make their seasonal inquiries about the possibility (and price) of having a beautiful new low water garden installed in their landscape. Of course, we are only too happy to provide vision, experience and direction to this wonderful process.
However, there are many important differences between low water plants and other more commonly used plants and we need to take these differences into account from the very start to ensure proper establishment. Most low water plants, and certainly most California native plants, tend to be much tougher and more resilient to our local weather extremes - this is of course only if the plant is being installed and watered correctly. Low water and California native plants typically need very little amendment or fertilizer and can tolerate minimal water and poor soil conditions but they also tend to be particularly sensitive to over-watering and over-moist soil conditions. Seeing that we work almost exclusively with low water and California native plants in the San Jose and San Fransisco Bay Area. We thought it may be helpful to cover a few of the essential techniques we use to ensure healthy, vibrant plant establishment when using low water plants in the urban landscape.
Establishment & Mortality: What Begins Well, Grows Well
Plant mortality is a common problem among young plants and newly installed gardens, especially in gardens which are installed during the heat of summer. This potential loss of plants is mainly due to shifts in the plants surrounding environment. Drastic changes in temperature, water transpiration and light exposure certainly play huge factors - but these tend to be endemic or unalterable aspects of ones micro-climate situation. Past growing your gardens indoors in heated greenhouses, no matter where the plant is in the landscape, regulated water application, soil health, drainage, suppressing weed growth and regular pruning are the main ways we can affect and protect plant health.
Of course every plant must be placed in the correct conditions to survive long-term based on its own unique needs. We, as gardeners or garden-stewards, can help without using any harsh chemicals or chemical fertilizers. Think about it - for thousands of years farmers simply did not have chemical herbicides or pesticides, relying solely on naturally occurring nutrient and mineral sources and sweat equity. While natural sources can't compete with the highly concentrated chemical elements, it does indicate that these same elements and nutrients are in nature everywhere found in abundance. We only need adequate motivation and foresight to put these elements to use.
Through the simple application of high plantings and copious mulch - with a bit of organic compost every so often, we can successfully solve or avoid many of the common issues which affect young, struggling low water and California native plants while creating ideal soil conditions and maintaining a healthy environment for you. In this small article we will be discussing the process and benefits of planting low water plants correctly, using mini-mulch to insulate and feed the root-level soil, building organic compost (soil building) and drip irrigation for adjustable water delivery.
Soil Texture & Quality: A-O-M
Soil quality is as variable as the weather. Here in California, specifically in the San Jose and San Francisco Bay Area we have a great deal of clay-heavy soil. To solve this, as our instructors at Foothill's wonderful Environmental Horticulture and Design program used to say, first we must recite the mystical soil mantra, AOM: Add Organic Material. By adding organic material (leaf clippings, plant material, compost) you can gradually re-supply the soil with the needed nutrients to attract the beneficial little insects which live and thrive in the soil.
The insects and other life forms in the soil, of which there are tens of thousands per square meter, aerate the soil and fix nutrients into forms the plants roots can use. The pests we find in the soil, one group of which are called Springtails (Collembola) are actually a "main biological agent(s) responsible for the control and the dissemination of soil microorganisms", even though we tend to think of most bugs or insects as pests. When the individual numbers of these living organisms are depleted, soil health can decline, leading the soil to become anaerobic (lacking air) which can attract weeds and other undesirables. A contemporary method of soil analysis focuses not only on the appearance of a specific elements & minerals in the soil, but in counting the number of insects and other living organisms in the soil to more accurately judge the soils viability.
Root-Soil Contact in the Planting Hole: Using Mycorrhizae Mycorrhizae is essentially an intelligent networking fungus (oh, don't be a sore spore!) which attaches itself to the roots of the plant and actually elongates the roots, which increases the plants root surface area which increases nutrient flow & availability. This fungus attaches itself to other functioning subsurface fungal networks and then mediates the passage of nutrients, air & water to all plants connected in the network. In this way, Mycorrhizae acts as a subsurface root enhancer and it's already found in nature.
In our experience, the usage of Mycorrhizae in new plantings has almost eliminated plant mortality and seems to super-charge the health and flower production of the plant itself, and it's all organic and non-toxic. Interestingly, this smart-fungi also seems to actually prey on unsuspecting organisms such as the aforementioned Springtails, "one of the most abundant of all macroscopic animals" with which the fungus procures a ready source of nitrogen.
To purchase Mycorrhizae as a powder form, one only has to search online for organic sources or even talk to someone at your local (gulp) Commercial Turf Supplier as Mycorrhizae is used on almost all turf & lawn applications at the professional level. It's surprising to see how few people actually use this fundamentally important fungus in low-water landscape installations.
*Please Note - Mycorrhizae is not suitable for some plants. Please be sure to inquire before application.
*Please Note - Mycorrhizae is not suitable for some plants. Please be sure to inquire before application.
Plants on a 3-4 inch high mini-mound: Don't Drown the Crown
Planting low water plants just a bit higher out of the soil serves two main purposes; it keeps the root-crown clean and dry, thereby avoiding rot and secondly, allows for deeper mulch application around the plant - the key to weed suppression. With 3-4 inches of mulch, weeds have a tougher time spreading roots and are easily hand pulled or turned with a flat-head shovel right on the surface of the mulch.
Planting low water plants just a bit higher out of the soil serves two main purposes; it keeps the root-crown clean and dry, thereby avoiding rot and secondly, allows for deeper mulch application around the plant - the key to weed suppression. With 3-4 inches of mulch, weeds have a tougher time spreading roots and are easily hand pulled or turned with a flat-head shovel right on the surface of the mulch.
As a general rule, any plant can become unhappy in poorly draining soil. Plants which are sitting too low in the soil can also become covered, sometimes over the root crown, by standing water. This can make low water or California native plants very sad. Plainly, most low water plants and trees should not be visibly sinking into the ground. Also, surrounding the plant or tree with rocks does nothing at all, except to needlessly compress the roots & root-crown. Avoid it or undo it if you can. A hard and fast rule is to leave the base & crown around any plant or tree as clear as possible, with the exception of appropriately spaced companion plantings and mulch. It's crucial for plant and tree health that air transpires evenly through the root & crown at the soil level. Stacking rocks in a tight circle around the base of any plant or tree is like affixing a small noose which only serves to stifle air & water passage.
Most low water plants and trees need to be planted notably above grade to allow for adequate mulch depth and to account for future sinkage, in that many plants & trees gain considerable mass and will often sink into the planting hole over the first 3-5 years. To avoid sinkage make sure that the planting mound is firmly packed and that you start with reasonably dry soil before planting. Many large plants sink due to overly wet soil during installation. As the soil dries, the excess water and air eventually evaporate through the surface or transpire through the plant, which creates tiny pockets of space around the root area of the plant, which leaves the plant low in the soil. This is not to suggest that the plant should not be well watered in, it should, but we should start with dry, firm soil.
Use 3-4 inches of mini-mulch or micro-mulch: Mulch is the Key
We use primarily micro-mulch or mini-mulch for a few simple but tested reasons. First, mini-mulch decomposes faster than larger gauge mulch chips, which means that you won't find the same tired mulch chips 20 years later in your front planting bed. During this natural decomposition process, micro-mulch actually becomes or creates new soil. Many kinds of mulch will be slightly acidic which is perfect for many types of low water plants & trees. Plus, we think it looks nicer, too.
Another great benefit of deep mulching is that it provides a degree of frost & heat insulation for plant roots and the micro-organisms which live in the soil. It's important to protect roots and soil organisms from frost in the winter and excess evaporation in the summer. Because mulch can help the soil retain water, it plays a vital link in the reduction of water usage. Coupled with low water & California native plants, we have worked in many situations where, with correct planting height, good draining soil and adequate mulch, many plants need little additional watering after the initial 6-12 months of establishment.
Using the correct drip irrigation system means that you can have very low cost, adjustable water flow delivery to each & every plant, even when all plants are on the same valve. Please visit us again to read more in our next installment Living with Low Water Plants, Part 2: Using Drip Irrigation.
Part 2: Using Drip Irrigation
We use primarily micro-mulch or mini-mulch for a few simple but tested reasons. First, mini-mulch decomposes faster than larger gauge mulch chips, which means that you won't find the same tired mulch chips 20 years later in your front planting bed. During this natural decomposition process, micro-mulch actually becomes or creates new soil. Many kinds of mulch will be slightly acidic which is perfect for many types of low water plants & trees. Plus, we think it looks nicer, too.
Another great benefit of deep mulching is that it provides a degree of frost & heat insulation for plant roots and the micro-organisms which live in the soil. It's important to protect roots and soil organisms from frost in the winter and excess evaporation in the summer. Because mulch can help the soil retain water, it plays a vital link in the reduction of water usage. Coupled with low water & California native plants, we have worked in many situations where, with correct planting height, good draining soil and adequate mulch, many plants need little additional watering after the initial 6-12 months of establishment.
Using the correct drip irrigation system means that you can have very low cost, adjustable water flow delivery to each & every plant, even when all plants are on the same valve. Please visit us again to read more in our next installment Living with Low Water Plants, Part 2: Using Drip Irrigation.
See more in our Living with Low Water Plants series:
Part 1: Plant Installation Part 2: Using Drip Irrigation
Part 5: Holistic Economics
All content (c)2010 Patrick & Topaze McCaffery
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