Thursday, September 3, 2015

Fall Cleanup Tips – Chapter II: The Annuals Ornamental Garden by Peter Drake

Photo courtesy
Beautiful to look at through the summer season, whether as a border to your house or walkway, or as an island on your lawn space, there is no need to despair when your annual ornamentals start wilting, browning and showing other signs of setting seeds and finishing out their life cycle.  
Indeed, if your annuals are already wilting, or showing other signs of stress, they may be completing their life cycle slightly early due to the intense heat we have experienced over these last several weeks.  Instead of responding to wilt and stress at this time of year by seeking to water more, or fertilize your existing plants, there are many cleanup and planning actions you can take with next season in mind to ensure that your annual ornamentals planting areas will be as beautiful in the future, if not more so. 

Any cleanup and planning you can do will be better served by observation-based questions you can answer about how your garden performed this year, based on what you planted and the specific microclimate conditions you may have experienced.  These questions can include, but are not limited to, the following:
  1. Have your annual plants suffered from any diseases this season, and if so, why?
  2. What was the condition of your soil this season?  Have you been regularly amending your soils with organic matter (compost) each season, and mulching around your plants to conserve moisture?
  3. Do you have structural factors that you need to consider each season, such as a building, tree or line of shrubs that throws shade over your planting area for a certain period of the day, or provides a windbreak, or funnels wind over your planting area?  Also, is there an area close by your planting area that could be a heat reservoir, such as a large concrete walkway or drive, or a stretch of landscape rock which absorbs and reflects solar heat, resulting in higher temperatures around and on that area? 
  4. How much have you watered your plants this season, and has that amount of water been truly necessary?
  5. How can you make certain that your planting area always has something growing in it, or is otherwise covered, through the winter months to minimize soil erosion, and improve soil fertility? 
Let’s take these questions one at a time.  In answering them, you should have the beginnings of a proactive plan you can return to for years to come.
Regarding diseases: Annual ornamentals are susceptible to a number of insect pests and diseases, including (for insects) varieties of aphid and spider mite and (for disease) varieties of canker, leaf spot and powdery mildew.  When cleaning up your planting area, observe your plants carefully and, if you observe any insect or disease presence, make certain you bag and dispose of any infested plant material separately, so that you reduce the chance of diseases and insects overwintering in your planting area.  If your plants have been heavily infested by a certain insect pest or disease, you may consider rotating your plant types next season to break cycles of insect pest infestation, and conducting a different style of plant care.  For example: if your annual ornamentals were heavily infested with powdery mildew (a common problem this season due to a cooler, wetter spring followed by conditions of intense heat) you might consider spacing your annuals slightly farther apart next season, and conducting more intense pruning and deadheading to ensure more open canopies and better air circulation in your plants to cut down the chances of this disease finding a home.
Regarding your soils: Annual ornamentals thrive best in a well-drained, loamy soil where the short-lived root masses can easily spread to access moisture and nutrients.  While Colorado soils are often hard-packed alkaline clay, or sandy (and an average residential lot is some combination of the two) you don’t need to wait for improving your soil until right before spring planting.  While cleaning out your wilting, dying annuals, you can amend your planting area with peat moss, garden compost or animal manure that has been aged for at least a year.
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Broadcasting these amendments evenly over the surface of your planting area and tilling them in to a depth of two or three inches will save you on work required to turn and prepare your planting area for new annuals in the spring.  Also, if you mulch your planting area during the fall with leaves (provided these leaves do not show signs of fungal disease or insect pests which could overwinter on them) and/or a woodchip/bark mulch, this will enable your planting area to retain a more consistent temperature and, therefore, a consistent degree of microbial activity throughout the winter, which will only improve soil texture and fertility.
Regarding structural factors, as they influence patterns of shade, sun, radiant heat and wind on your planting area, close observation of how much sun, shade and wind your planting area has received this season can assist you in looking more closely at the needs of each plant you have selected in the past, and could select in the future.  If you have one end of a planting area that is, for instance, in sun six to eight hours of the day, and adjacent to a concrete drive or walkway, you would want to make certain, during your cleanup, that you amend that part of the planting area more generously and thoroughly to ensure the best ongoing soil texture for the resilience of your plants in any extreme of sun and radiant heat.  Also, for next season, you would select plants for that space that perform best in continual heat and sun.
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Regarding water: even the most practiced gardener finds the balance between too much and two little water difficult to maintain.  It has been especially challenging this season because, again, a cooler, wetter spring abruptly shifted to an intensely hot July-August window, and many an annuals planting area showed stress simply from the plants attempting to adjust.  During your fall cleanup, as you remove plant debris, amend your soil, and mulch, you should work your hands into all spaces of your planting area.  Is there any part of your annuals bed that feels notably drier or wetter?  This could denote a difference in soil texture encouraging swifter, or slower, drainage of existing water.  You can correct this over time by more thorough and uniform soil amending, by planting next season to take advantage of any variable moisture retention characteristics of your soil, and by watering to allow for any variation in those characteristics: if you know one part of your planting area will, naturally, hold more water than another for a longer period, simply water it less often than other parts of your planting area.
Finally, regarding always keeping plants growing in your soil: while soil amendments and mulching over your annuals bed can help to preserve and enhance your soil for next season, you can also plant anew as you clean up for the fall, ensuring some visible color and life in your planting area as we move into winter, while also maintaining higher, healthier microbial life in the soil, and providing root matter to hold the soil in place against wind and water erosion.  The range of flowering plants suitable for fall and winter conditions is, of course, much more limited.  However, certain varieties of pansies and petunias are more resilient to colder conditions, and these are a good place to start for researching what would do best in your garden at this time.  You can also explore the possibility of conducting a fall planting of certain types of bulbs and corms for flowering in the spring.  Or, if you do not choose either of these alternatives, it would still be wise to, following fall cleanup, sow a cover crop of a simple annual, such as annual ryegrass, over your planting area.  This grass, if sown by mid-September (as with any other grass, you would first evenly till and amend the soil, broadcast the seed evenly, rake the seed so that it is in even contact with the soil, but not buried, mulched with clean straw, and then watered in) will germinate to form sufficient coverage over your planting area.  While it will be killed by the first frost, this grass will successfully hold soils in place and, if you till it in a month before you intend to plant next spring, it will decompose to add nutrients to your soil, and improve your soil’s texture.
In conclusion, then, you have a broad range of possible courses of action within your control as an annuals gardener for your planting space.  Aside from the non-negotiable forces of nature, you can continually improve your soil and plant appropriately for almost any condition of sun, shade and water to ensure that each part of your planting space is appropriately, and attractively, utilized for your full enjoyment, and the enjoyment of other people, and pollinators, each season.
Selecting, Buying and Planting Annuals and Perennials