Fall is here and it's time to address the veggie garden. Fall is, in most locations, the best time to think about re-organizing, planning, and scheduling your upcoming crops. It is also the best time to get manure and compost into the garden, plant perennial crops, vines, and trees, as well as adding a fresh layer of mulch. Most gardeners don't get to the dreamy planning stage of gardening until late December when all is dormant, days are short, and the seed catalogs have come... but that's really too late for this winter's crops and even for getting a head-start on next spring. Below I've put together some ideas for consideration:
Putting the Garden to Rest:
Traditionally, the gardener had two options... let the land go "fallow", or put in a "cover crop". Here in Marin we've got more options- and for this we're grateful, but we now know that the "fallow" option is not a good one, no matter where you garden. Leaving soil bare invites erosion and depletes the soil biological diversity and activity. At the very least, a heavy layer of organic mulch should be applied so the earthworms and the rest of the remaining soil ecology has some food, is protected from temperature extremes, and hopefully, the possibility of either water or wind erosion is reduced as well as reducing any wind-blown weed seeds from germinating.
A better solution would be to use a cover crop. A "green manure" crop, as they're sometimes referred to, is generally a mix of a legume and a winter grass; the legume helping to add nitrogen and the grass to increase Organic Matter,"OM", in the form of cellulose -hydrocarbons. The legume would increase nitrogen through a symbiotic relationship with the bacteria Rhizobia that inhabit the roots of the plants and fixes nitrogen from the atmospheric nitrogen found in air within the pore spaces of the soil. A legume cover crop can add around 80 lbs of nitrogen per acre. The other concept is that the "rhizosphere" is kept alive... we now know that plants have co-evolved with various ecto- and endo- mycorrhizae fungi that help them breakdown, transport, and uptake nutrients into their roots in exchange for sugar. These populations of fungi plummet when the living root matrix is removed from the soil ecology. Keeping a crop in the soil helps maintain increased and balanced populations of beneficial fungi, bacteria, and other soil organisms. Vetch and Rye is a good combination of a legume and a grasse, as are other blends incorporating clover or beans. Fava beans are a favorite as they can also be eaten (edamame) and also grow to impressive size which is good for weed suppression and for younger gardeners who are impressed and inspired by the plants.
In the home garden, space and time is usually limited and the three to four weeks that most cover crops take to decompose after being tilled or disked under is too long to wait. This can be easily remedied by harvesting the cover crop for the compost and putting finished compost back in it's place. This way, the garden returns to production, the soil ecology maintains good populations, and the compost gets a big burst of nitrogen and organic matter to heat it up. This makes no sense, of course, if you're dealing with any sizable agriculture, but the typical back yard raised bed and compost systems can benefit from the quick switch. That having been said, one must really think about other options before devoting precious soil space to a cover crop. Legumes should be part of a regular crop rotation program anyway, and most crops can provide a ready supply of organic matter for the compost. In addition, ready-made compost is now available from local suppliers who are working diligently to reduce the amount of green waste going to the landfill. Supporting our local resource recovery and composting facilities is important and many now offer certified organic composts at very reasonable prices.
Adding compost to the soil is most important in the fall. Our winter rains stir up the earthworms and other soil biota and the organic matter is converted into active humus, releasing more nutrients, and helping to build better soil structure for the following season's crops. Humus is the glue that holds the texture of the soil -sand, silt, and clay- together into soil aggregates and allows for better tilth -increased soil pore space that equates to increased aeration, water infiltration, and water holding capacity. If budget allows, for the small home garden, adding bulk compost and continuing with productive food crops might make the most sense, keeping the available space alive, active, and productive year-round.
Fall and Winter Crops are all about night-time and soil temperatures. Not much happens when everything goes below 50 degrees. One can think about the Winter garden as a huge outdoor refrigerator, keeping greens, tubers, and stems fresh for harvesting or overwintering for a head start on spring. The trick is to get your crops far enough along to be able to harvest throughout the coldest days and then keep the beds warm as long as possible and protect the plants from extreme conditions -prolonged frosts and pounding wind and rain.
Raised Beds help a lot. By just adding regular helpings of Organic Matter -"OM" and digging, the planting beds will naturally be higher than the paths in between. Just a few inches may make the difference between frosted and non-frosted plants. Raised beds can help add much more height and warmth, not to mention a great framework for garden organization, helping to schedule crop rotations, intercropping, succession planting, and companion planting programs. They also help reduce compaction as they are designed to eliminate the need to walk on the garden beds. Raised beds also form a good framework on which to apply cold frame "lights" to help protect plants in the worst of conditions. Here in Marin, there is generally more damage done from inadequate venting of cold frames -they can get really hot even in the winter!, but wax-based pistons can help automate this task and reduce the risk of cooking the plants you are trying to save from frost. The ideal top day-time temperature in a cold frame is in the 60-65 range... perfect for the plants to harden off and prepare for the cooler nights ahead.
One tool in our toolbox for frost (and pest!) protection is the floating row cover. These fine spun fabrics can go right over the crops, or be suspended by metal or pvc hoops, wires or poles, to protect most crops from a number of various pests along with protection from frost. (Think camping in a tent vs. out in the open on bare ground...) They are fine enough to allow light and water to penetrate, but still offer protection -usually 4-8 degrees difference. I've also found these especially helpful in mitigating the effects of leaf miners on chard, spinach, and other brassica plants, not to mention birds, raccoons, and even pets. When things get really cold, shade cloth and burlap tarps an also add layers of protection. In those dire situations where we dip below freezing, all these measures, along with irrigation, can work synergistically to keep fresh greens on your menu.
Biology equals heat. As a side note, I've heard of many stories of fresh manure and straw being placed below raised beds to keep them warm as well as chickens being used as a heat source for greenhouses. Frost protection is an open playing field for the gardener with ingenuity and persistence. Routing the dryer vent into a greenhouse might make a lot of sense.
Hygene vs. Habitat:
Winter is the traditional time to clean up the garden and eliminate sources of fungal spores and such from reintroducing themselves to next season's growth. While this makes sense, one has to take the whole Web into consideration and think about how the beneficials will overwinter. Our biological buddies are out there working at reducing our pest populations naturally and for free. Eliminating their winter food and habitat will be at our loss the following season. The old system of stripping the land bare, burning the pile of debris, and starting over in spring has given way to a new paradigm of knowing our pests and their natural predators, and promoting healthy populations of beneficial organisms that, along with proper cultural techniques, keep pest populations in a low, stable population that is below our acceptable threshold but high enough to support the population of beneficials. With this in mind, for example, it IS important to make sure that rose and peach leaves get removed and composted -to reduce various fungus diseases from completing their life cycle- but it might be good to leave some of the herbs as well as some composite and umbelliferous plants in place to allow for parasitic wasps to have a nectar source. Be on the lookout for Lacewing eggs, aphid mummies, and other signs of our natural garden helpers. A healthy and biologically diverse garden ecology will remain healthy while a bare bones sterile environment is a prime candidate for pest explosions in the spring.
While on the topic of pests... our first rains around Halloween also mean the start of our mollusk season. While this may not be as exciting as the deer or duck season to some hunters, snails and slugs can be easily trapped in citrus rinds, various trap crops, or killed outright with iron phosphate... an ingenious use of an effective bait that is also a fertilizer -and not toxic to pets, kids, or the environment when used as directed. This is especially true for those acid loving plants that tend to become iron deficient in alkali situations. Placing a meager bounty on the heads of these one-footed foes can also entice children to scour the garden for spare change. Again, know thy pest and where they hide.
Mud and Darkness:
As the garden gets closer to the Winter solstice, two elements help keep the gardener away: The mud and the dark. Both these problems can be easily solved: Address the garden paths in the early Fall and add a key tool to the garden tool box: a head lamp. Adding a fresh layer of wood chips, rice straw, or some other mulch -with a layer of cardboard or weed fabric if needed/desired, can quickly eliminate the mud -and the reluctance to venture quickly out there to cut greens and herbs. Likewise, a lightweight headlamp hanging by the door along with your pruners can eliminate the other hinderance to winter gardening and open up a whole new world for those who get home from work after dark and "can't" garden...
I've identified over 25 good candidates to consider for the Fall/Winter garden but I'm going to save this for a follow up Blog. Those of you in Marin who are interested in this topic and missed my two recent Seminars at Sloat Garden Center can hear more on this subject this Thursday at the Marin Art and Garden Center for the first Continuing Education event of the Marin Mater Gardener Program. It starts at 6:30.