With winter just around the corner, now's the time for gardeners to put some finishing touches on their planting beds before rains make turning the soil impossible, and freezes do damage to those half-hardy, herbaceous perennials.
Amending the soil in fall can pay dividends come spring because garden success is directly linked to soil fertility. But just as important as nutrients is the soil itself.
Microscopic bacteria and fungi help plant roots absorb needed nutrients and assist decomposition by converting organic matter to a chemical form that plant roots can absorb. In addition, earthworms aerate the soil while feeding on organic matter and leaving their nutrient-rich castings behind as plant food.
The worms and soil bacteria thrive in soils enriched on a regular basis with organic matter. For centuries, farmers have been applying manure to their fields, and today's gardeners can do the same. A 3- to 4-inch layer of manure combined with bone and kelp meals turned into planting beds in fall will make stronger plants come spring. Fertilizer still will need to be applied in spring, but the "grow-ability" of the soil will have improved.
What to Add
Manure is an energy source and food for earthworms and soil bacteria, which convert the organic matter in manure to a fertilizer structure that plant roots can readily absorb. Bagged, composted manure is convenient for small gardens, while those with larger gardens can purchase aged manure from a local compost company or farmer at much more reasonable prices than bagged products. Spread a 3- to 4-inch layer of cow, steer or horse manure over the bed and turn under, thoroughly mixing with the garden soil.
Bone meal is an organic fertilizer that contains high amount of phosphorus, an extremely important element needed for flower and fruit development. Phosphorus is slow to break down in the soil. As a result, continual applications twice per year help guarantee an ample supply. The application rate of bone meal is 3 cups per 100 square feet.
Kelp meal, a dried seaweed without the salt, is a natural source of trace elements required by plants in minute amounts. A twice-per-year application is recommended at 2 cups per 100 square feet.
Apply all three components over the planting bed and turn under. In addition, fall tilling helps reduce overwintering insect pests that hibernate near the soil's surface. Dislodging them from their comfy dens exposes eggs and larvae to winter elements.
Preparing Perennials for winter
Protecting herbaceous perennials is an easily overlooked fall task, especially when mild temperatures are the norm and winter's cold seems to slowly sneak up on gardeners. Herbaceous perennials are those plants that send up growth in spring, bloom in summer or fall, then die back, their crowns going dormant through the winter.
In the vegetable garden, herbaceous perennials include asparagus, artichokes, horseradish and rhubarb. Of the four, artichokes are most vulnerable to freezing out when temperatures drop to the low 20s or teens. A protective layer of hay or straw mulch over the plant's crown through the winter can be the difference between survival and spring replanting.
In spring, when the soil starts to warm and growth begins, the mulch is pulled away to allow sun to reach the plant's crown.
Asparagus is another example of a cold-tolerant perennial that could benefit from an overwintering mulch. In late fall, cut asparagus plants back to just above ground level, and mulch the bed with hay or straw to keep the bed from freezing and to encourage roots to slowly grow through the winter. When shoots begin to sprout in spring, remove the mulch.
Raised beds of asparagus have the advantage of producing spears earlier in spring than plants growing at ground level, but raised beds also are more vulnerable to freezing during extended periods of cold than ground-level planting. Newly established asparagus beds can really benefit from a winter mulch.
The timing of winter's onset is a factor in the severity of plant damage. Late-fall cold snaps can cause more damage to plants than mid-winter freezes, as plants still are not in full dormancy during late November and early December.
In addition to organic mulches, gardeners can protect plants during cold snaps by covering them with a frost fabric, such as Reemay. The spun-polyester blanket can offer 5 to 7 degrees of freeze protection — even more when double layers are used.
This material protects fall lettuce, greens and broccoli when temperatures take a sudden drop. Although plants may survive without protection, the tender leaves and flowers of broccoli are the first to become frost-burned. Available in many garden centers, frost fabric is one of the gardener's best weapons against unseasonable cold.
Cold snaps happen every winter, and some are more extreme than others. Being prepared and taking action when the temperatures drop can make the difference between plant survival and replanting in spring. Keeping a watchful eye on overnight forecasts is just one more strategy for successful gardening.
David James has been writing gardening stories in Southern Oregon for 35 years. Contact him at firstname.lastname@example.org.