SOIL PH FOR GROWING VEGETABLES

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Soil pH is a measure of acidity or alkalinity.  This measurement can range from a very low pH of 1.0 to an extremely high pH of 14.0.  7.0 is considered neutral and several vegetables will thrive in soil with a neutral pH.  Some vegetables do prefer a more acidic soil while others prefer a more alkaline soil.  Fortunately most will grow and produce well in a pH range of 5.5 to 7.5.   Areas with high rainfall, such as coastal Washington, tend to have acidic soils high in organic matter, while areas with lower rainfall, such as most of the mountain valleys in Montana, tend to have alkaline soils low in organic matter.  Here in the valleys of the Flathead region, where most of us garden, soils tend to be somewhat to highly alkaline.

Before you amend your existing soil to plant vegetables it is a good idea to test the pH.  An easy way is to purchase a test kit.  Most of them are easy to use and give fairly accurate readings.  Your county extension agent can do a soil test also.  Once you have determined your soil pH and which crops you intend to grow, you can amend your garden soil.  Adding lime will increase pH and make acidic soils more alkaline; adding sulfur will lower pH and make soils more acidic.  Organic matter usually helps reduce alkalinity.  Aged manure, pine needles, compost and coir dust are a few amendments that will help do this while they improve soil structure and encourage beneficial soil micro-organisms.  If your garden is divided into separate beds or raised beds, it is easier to adjust the soil in each bed for what you plan to grow.   I rotate my vegetable crops in a four-year rotation plan, so I try to keep a basic soil pH around 6.0 to 6.5.  This way I can grow almost every vegetable, but I slightly adjust pH each year before growing a particular plant.  For example, I add sulfur before growing potatoes.  Conversely, I add a small amount of lime before planting any of the Brassica family (Broccoli, Brussels sprouts, cauliflower, etc.).   Having soil pH correct for each crop will reduce pest and disease problems as well as increase yields.

Here is a listing of pH tolerance ranges for specific vegetables.  (The optimum pH for each is usually the median between the two extremes.)  I have listed vegetables preferring more acidic soils first and those preferring more alkaline soils last:

Potatoes, 4.5-6.0; sweet potatoes, 5.6-6.5; horseradish and rhubarb, 5.5-6.8; butternut squash, carrots, corn, eggplant, lettuce, peanuts, peppers, pumpkins and watermelon, 5.5-7.0; cucumbers, garlic, winter squash, and tomatoes, 5.5-7.5;  celery, 5.9-6.9; soybeans and strawberries, 6.0-6.8; onions, radishes, shallots and spinach, 6.0-7.0; beets, any of the Brassica family, peas, summer squash, Swiss chard, and zucchini, 6.0-7.5; okra, 6.0-8.0.

 

April Gardening Calendar

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April is another busy month for gardeners; usually a month characterized by ups and downs in temperature.  Keep watch for frosts; protect cold frames with mats if frosts are imminent, and admit air daily as weather permits.  Finish pruning fruit trees if not done, plant grapes; fertilize and prune blackberries.  Check your fruit trees and roses for pests as soon as they bud and leaf out and set out apple pest traps two weeks before bud break.  Weed and amend all your beds now while it is cool and moist.

Finish planting fruit trees, shrubs, roses, and perennials.  This month is a good time to direct sow (where they are to flower)seeds of several flowers: sweet alyssum, cornflowers, carnations, pinks, poppies, stocks, rose campion, Lychnis, columbines, valerian, honesty, foxglove, snapdragons, mignonette, larkspur, kiss-me-by-the-garden-gate and four-o’clocks.  Perennials still may be divided if weather has not become too warm.  Violets can be divided after blooming and cuttings taken of pansies.  Make cuttings of chrysanthemums, gauras, Helianthus, lupines, Lychnis, Liatris, knautias, saponarias, scutellarias and veronicas.  Dahlias and tigridias may be started inside in cold climates and planted out later after frosts are over, or planted outside if the soil temperature is above 60 degrees F.

Several vegetables can be direct sown if weather permits and it is not too cold: beets, arugula, carrots, caraway, celery, chervil, chives, cilantro, dill, fennel, collards, mache, fava beans, cress, kale, Jerusalem artichokes, kohlrabi, leeks, lettuce, mustard greens, rhubarb, turnip greens, onions, pasley, parsnips, peas, potatoes, radishes, salsify, scallions, spinach and Swiss chard.  Sunflowers and tomatillos can be sown two weeks before the last expected frost.

Corn may be sown after April 15th in cool maritime northwest climates, or a week or two later in the inland and mountain areas.  Usually corn is sown about 10 days to two weeks before the last frost.  Native Americans of the Hidatsa tribe living in the Dakotas planted sunflowers first, then corn, and after frosts followed with beans and finally, squash.  Sunflowers were grown by themselves in a field, but corn, beans and squash were grown together; with corn in hills of 6-8 and beans and squash vining through.

Vegetables started last month indoors may be planted out this month: the brassicas, parsley, Asian greens, rhubarb and tomatoes; once frosts are over.

Prune established roses before bud break and seal the cuts with water-based glue or wood glue.  This prevents drilling wasps from injuring the canes.  Fertilize organically with Epsom salts, manure or compost, bone meal or rock phosphate, alfalfa meal and seaweed or wood ashes.

A few things maybe grafted now: grapes, hollies, pears, maples, pines and clematis.  Layers can be made of Cotoneaster, Cotinus, Hydrangea, Lavandula, Lonicera and Parthenocissus. 

Enjoy spring!

Growing Asparagus

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Asparagus (Asparagus officionalis) is a popular vegetable today and was quite popular in the nineteenth century.  The photograph above is of an antique variety, ‘Giant Asparagus’ an engraving from The Illustrated London News, dated 1851.  An asparagus knife is shown alongside the plant.  This year, I grew another old variety of asparagus from seed, ‘Connover’s Collosal’, dating to the second half of the nineteenth century.   It is difficult to find plants of heirloom varieties of asparagus, so one has to start them from seed.  However, the process is slow, as the plants take three to four years to reach the size for harvesting.  (If too many shoots are cut from very young plants, productivity may be reduced, or the plants may die.  But if the plants are allowed to become established, an asparagus bed will last twenty years or more, even up to fifty years!)

Late March into early April is an excellent time to start asparagus from seed.  Use a sterile medium, cover the seed about 1/4 inch deep and place the pots in a warm location (77 degrees is optimum).  The seeds should come up in about ten days.  You may direct seed into a bed if soil temperatures are above 50 degrees, it will just take a little longer for the seeds to germinate.  Asparagus plants begin to grow slowly and will not be ready to transplant out for about three or four months.  Meanwhile you can prepare a bed for them.  An ideal spot is in full sun with a bed large enough to accommodate the number of plants you need.  It is usually recommended to plant five to six plants per person.  Since the plants are perennial (USDA climate zones 4-9) they benefit from a well-prepared bed.  Peter Henderson, in his book Gardening for Profit published in 1867, recommended planting transplants nine inches apart in rows three feet wide for commercial growers, or two feet wide for home gardeners.

Once you have established how many plants you need, you can make the planting bed.  Henderson recommended trenching the bed two to three feet deep with about three inches of rotted manure mixed into the soil.  A deep sandy loam is best for them as they are native to alluvial soils.  Bernard Mc Mahon, in Mc Mahon’s American Gardener, published in 1857, recommended double digging two spades deep and placing several inches of rotted manure in the trench, then spreading another layer of rotted manure over the surface.  He directed gardeners to mix this second layer of manure with the soil to a depth of eight to ten inches.  My young plants, now a year old, have spears a little larger in diameter than a toothpick.  The young plants may be grown in a temporary (sunny) rich bed for another year, then moved to their permanent location.  Place the crowns of the plants two inches below the soil surface.  Keep the beds weeded to ensure quick, even growth.  Mc Mahon recommends three years from planting (which would be four years from sowing seed) before cutting can begin.  Dress the bed every spring with rotted manure, bone meal and wood ashes.

If your family really enjoys asparagus, plant more than five plants per person; I plant twelve per person.  If you plant two-year transplants, spread the roots out like the spokes of a wheel and cover with about one inch of prepared soil.  Water well.  As the plants grow, cover them with more soil until you have them two inches under.  Do not use fresh manure as it will burn them and (heaven forbid) do not use chemical fertilizers, especially on newly planted asparagus.  Wait two years to begin cutting.  A summer mulch of three inches of straw is excellent, will protect the plants in winter and the spears will come up earlier in the spring if the ground is not frozen too deeply.

When you cut asparagus spears get them into the refrigerator right away or cook them immediately because they lose flavor as quickly as sweet corn does.   Considering how expensive asparagus is, I find the start up work well worth while.  Enjoy!