NEW TO GARDENING?  TIPS FOR SUCCESS IN A HARSH CLIMATE

 by Kelly Grummons, owner of and horticulturist for Timberline Gardens, Arvada, CO

GARDENING IN A CLIMATE OF EXTREMES.  Our region experiences tremendous temperature fluctuations in spring and fall which can severely damage plants especially those not well acclimated (Elm trees in 1989). Planting in the spring often gives plants more time to acclimate than those planted in the fall.

 I.          AMENDING THE SOIL.  The soils in this region tend to be very clay-like or very sandy. Both of these soil types drain poorly. Adding various amendments will improve the porosity and oxygen content of the soil which is important for plant health and establishment. Amendment technique depends upon the type of plants being grown.

                           A.        AMENDING THE SOIL FOR HIGH WATER/FAST GROWING PLANTS such as vegetable gardens, annual beds, moisture-loving perennials, and high moisture turf grasses.

                                            1.        Add Composts made of recycled yard waste (tree trimmings, grass clippings and leaves).  Manure can be a useful additive with these types of plants, but may be high in phosphorous.

                                            2.        Add up to 30% by volume of this vegetable-based compost (2 inches on top, tilled in 6-8” deep). This type of compost is low in soluble nutrients and is not a substitute for fertilizer. Compost is not fertilizer, it is soil amendment.

                           B.        AMENDING THE SOIL FOR NATIVE AND OTHER XERIC PLANTS that don’t benefit in the long run from high levels of organic matter. (Plants like rabbit-brush, Russian sage, native cacti, yucca, agave, penstemon, etc.). These plants may seem to respond enthusiastically initially to the compost, but in the long run may be damaged by the excess moisture and associated microbes held by the compost.

                                            1.        Amend level (flat) ground with 10-15% vegetable-based compost and 30-50% small aggregate (stone) such as squeegee (1/8 – 1/4 inch), pea gravel (1/4 – 1/2 inch), expanded shale, volcanic rock, etc. and till in 8-12 inches deep.

                                            2.        To further improve drainage, add amended soil in “berms” on top of your already amended level ground. This will maximize the drainage of your beds. Aggregates and compost as well as mycorrhizal inoculants will keep clay particles from binding together.

                                           3.        Suggested “berm” mix:  60^ clay loam or sandy loam, 10% vegetable based compost, 30% squeegee or other aggregate. This can usually be mixed at the bulk yard and delivered to your site.

                                            4.        To maximize drainage from the berm into the ground, apply several inches of berm mix and till into ground mix then install the rest of the berm mix. This will prevent different soil textures from forming layers that could cause drainage problems.

                                            5.        Remember that it’s always best to amend the soil in large areas (whole beds) rather than just amending the soil around each plant’s root ball.

   II.          ADDING SOIL INOCULANTS  Universities (CSU and Texas A&M) have done extensive research on the use of fungi (mycorrhizae) that have a beneficial symbiotic relationship with plants in the garden. Applying mycorrhizal fungi to the roots of landscape plants can greatly increase the plant’s survivability and viability.

                           A.        The mycorrhizal spores come in a dry culture (like yeast) mixed with a carrier like vermiculite. The powder is dusted onto a moist root ball. The fungus’ success relies upon the spores being able to germinate and attach to the root. Applying the culture to the root ball at transplant time is the most effective method. The culture can also be applied to the roots of an established plant by injecting it into the root area as a powder or liquid.

                           B.        The mycelia (root-like structures) of the beneficial fungi permeate the clay particles much better than the plant’s own roots which makes water and nutrients more available to the plant.  The mycorrhizae can also ward off harmful diseases.

                           C.        Mycorrhizal cultures like “Myke” contain fungal species which can colonize most types of plants except the families that represent rhododendrons and azaleas, heathers, heaths, blueberries, orchids, carnations and a few other species.

                           D.        University tests (CSU) have shown that phosphorous levels above 50 ppm can harm the fungi’s association and effectiveness and levels above 100 ppm can kill the beneficial fungi.

                                            1.        Most native soils are in an acceptable range of phosphorus for these fungi.  Soils in areas that were agricultural or soils harvested from agricultural areas are often too high in phosphorus to support the fungi.  It is advisable to have a laboratory test the soil before investing in the cultures as they are relatively expensive.

                                            2.        Also test soil mixes such as “planter’s mix” as manure may have been used in the mix which can be high in phosphorus.

                                            3.        Avoid high phosphorus fertilizers like “Miracle Gro” as they are too high in phosphorus.

                                            4.        Alfalfa or kelp-based fertilizers are ideal in the culture of both plants and mycorrhizae.

                                            5.        Species specific fungi are available from companies like ”Dr Mike” Mike Amaranthus, PhD. from Mycorrhizal Applications, Inc. (info@Mycorrhizae.com), 541-476-3985, or 86-476-3985. Their expertise in these applications is excellent.

                                            6.        Some fungicides are toxic to mycorrhizae. Check with the folks at Mycorrhizae.com for a list of safe and or toxic fungicides.

  III.          PLANT NUTRITION IN OUR HARSH ENVIRONMENT (FEED THE WORMS)

                           A.        WHY USE ORGANIC FERTILIZERS?  Because our soils drain poorly and also since water restrictions and the higher cost of using water in the landscape, salts don’t get leached away and become trapped in the upper levels of the soil profile.

                                            1.        High salts cause stress to the plant making it unable to uptake water nutrients effectively. This causes poor performance and symptoms like needle burn on pine trees.

                                            2.        Fertilizers based on alfalfa meal, kelp meal or sea kelp extract are low in soluble salts and are excellent, stable forms of plant nutrition.

                                            3.        Earthworms are extremely important in the translocation of nutrients in the soil and in providing aeration in poorly drained soils. Earthworms don’t thrive in salty soils. Worms are highly attracted to nutrient sources like alfalfa meal or kelp meal.

                           B.        USE ORGANIC FERTILIZERS IN CONTAINER GARDENS

                                            1.        In containers, the soil temperature often reaches the ambient air temperature. Nitrogen from chemical sources tends to volatilize at 80° F. That’s why plants in containers (especially hanging plants) often look malnourished. At high temperatures the nitrogen leaves the soil within hours.

                                            2.        Organic nitrogen sources like alfalfa or kelp meal, sea kelp extract, blood meal, etc. break down very slowly and are a more stable source of nitrogen in high temperature situations.

                                            3.        In high temperature areas, fertilize frequently with a combination of chemical and organic fertilizers for excellent results. In cooler locations, just organic fertilizer will be adequate.

                                            4.        For indoor potted plants, liquid kelp sources work very well for most plants. Specialty fertilizers may be supplemented for certain situations. Granular alfalfa or kelp may encourage fungus gnats in indoor pots.

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