March 28 2024: Weeding, wireworms, sowing, using lime

From Linda Gilkeson:

With the season coming along early this year, everyone wants to get gardening. While sandy and well-drained soil can be handled sooner than clay soils, after all the recent rain all soil is still much too wet to be dug or handled. So for now, stick to weeding, cleaning up debris and raking mulch back to allow the soil to warm up on the first beds you intend to plant; some seeds can be sown on the soil surface (see below).

Weeding: Weeds to watch for include the winter annuals, such as that small mustard family plant, hairy bittercress (google Cardamine hirsuta to see what it looks like). They have been germinating since mid-winter and are well on their way to making seeds that pop from the tiny seed pods all over the garden (the leaves make a tasty peppery addition to a salad). It is especially important to remove weeds, especially grasses, from vegetable beds to avoid attracting wireworm adults (called click beetles) to lay their eggs in the garden. The beetles lay eggs on plants, preferring grasses, in early spring. When the eggs hatch, the larvae or “wireworms”, burrow through the soil where they feed for the next 4 years on roots, boring holes in potatoes, onions, carrots, crowns of lettuce, even large seeds. If you planted fall rye as a cover crop for vegetable beds, cut it down and smother it in place with opaque covers (cardboard, tarps) or under a thick mulch of leaves, straw, etc., to kill it. The point is to make sure there are no living blades of grass or other weeds to attract the beetles as they don’t lay their eggs on mulch or in bare soil. For a home veggie garden, because of the wireworm problem, it is better to build organic matter in the soil by using compost and surface mulches than it is to plant overwintering cover crops.

Wireworm traps: While I’m on the subject of wireworms, here is a trapping tip: After clearing the garden bed of all weeds, skewer chunks of potato on sticks and bury them an inch or two deep here and there throughout the bed. As the soil warms and the insects become more active they will move through the soil to bore into the potato pieces. Every few days pull up each trap and destroy any wireworms in the potato, replace the traps and keep checking them until it is time to plant the bed. Not only does this catch a lot of wireworms, it will also tell you how much of a problem you have so you can redouble your trapping efforts or avoid planting roots crops in beds with the most wireworms. For photos of click beetles, wireworms and a potato trap:

What to plant right now: Direct sowing outdoors, by poking pea seeds into the mud or by scattering seeds of annuals (such as lettuce, spinach, radishes, cilantro, dill) on the surface works well while the soil is still too wet to disturb. Scatter the seeds on the soil, then press them lightly into the soil without covering them, or put some soil in a bucket and keep it where it will dry out and use it to crumble over the seeds. Seeds usually come up surprisingly early, but be prepared to sow more if we have bad weather and they don’t make it (or if slugs, cutworms and other critters get them). Do protect seedbeds from birds by covering with wire mesh, screening, floating row covers, to prevent them from eating the seeds. One of the best investments I ever made was to make box-like covers out of 1-inch welded wire mesh/”hardware cloth” to fit my garden beds. The galvanized wire comes in different widths at lumber yards (I used the 4-foot wide wire) and is easily bent to make self-supporting, sturdy, light-weight covers.

Other planting in the next few weeks:
-Peas can be planted outdoors, but the will germinate slowly. Germinating peas indoors and planting them out after 2- 3 weeks give much quicker results than sowing seeds directly in the garden at this time of year.
-Main crop potatoes don’t need to planted for another month, but you can put in a few early plants now for early new potatoes.
-Plant strawberries, fruit trees, berry bushes, asparagus.
-Start tomatoes, summer cabbage, cauliflower and broccoli seeds indoors under grow lights or in a heated greenhouse. I wait until early April to start squash, cucumber and melon seeds. If you can, set seedlings outdoors in direct sunshine for a couple of hours whenever we have a warm, sunny day. They will be healthier and by the time they are planted out, will be used to full-spectrum sunlight and less likely to be sunburned.

ABCs Enriching the Soil Part 2: Amending soil with limestone
If you are following along with these messages for beginning gardeners, you may now have the results of a pH test on your garden soil in hand. If the test shows a pH is above 6.5 or if the lab results state that pH is acceptable the soil won’t need lime. However, if the pH is lower than 6.5, you will need to mix horticultural limestone into the soil to grow vegetables well. Soil chemistry is complicated and the properties of the soil (sandy or clay, high or low in organic matter) and the type of limestone used affects how quickly you can modify soil pH, but general guidelines below should suffice for most home garden soils.

Ground up limestone is a natural product, sold at any garden center or agricultural supplier. Calcitic lime comes from rocks that are mostly calcium carbonate, while dolomitic lime comes from a type of limestone that contains both calcium and magnesium, making it a good amendment for most coastal soils. Depending on what is available at your local supplier you may or may not have a choice, but either type of lime is fine. Horticulture limestone is ground so that it contains particles ranging from fine dust to small sand. The finer particles act more quickly to modify pH, while the larger particles work over a period of years. Prilled lime products contains calcitic lime that has been made into pellets so that it can be evenly spread on lawns with a fertilizer spreader; it is fine for a garden too, but costs more. The only lime not to use is hydrated or builder’s lime from a builders supply as it can burn plants.

Lime can be applied any time–even immediately before planting–because it is a rock dust and won’t burn plants, however, it takes a few years to modify soil pH. If you started with native soil with a pH of 5.5, it can take a couple of seasons to raise it to 6.5. It is important not to overdo lime, however, so a general guideline is to spread about ½ kg lime per square meter (1 lb/square yard) once a year. If there are recommendations for how much to use on your soil test report, follow those instead. Test the soil pH after 3 or 4 years to see if you are on track. Once the pH is above 6.5, stop liming for a couple of seasons and retest in a couple of years as soil pH gradually declines due to the effect of winter rainfall and as plants take up calcium. Despite the desirability of minimizing soil disturbance, lime should be well mixed into the top 15 cm (6 inches) of soil because it isn’t soluble and moves very slowly down into the soil on its own. You can keep soil disturbance to a minimum by applying all amendments for the season at the same time (i.e., lime, compost and organic fertilizers–covered in future notes) and mixing them into the top layer of soil. Just fork or stir the soil to mix it well without turning it over or digging it deeply.

Republished with permission from Linda Gilkeson’s Gardening Tips. See Linda’s website to sign up for her newsletter, purchase books, access free presentations and identify pests and diseases which may affect West Coast gardens.

Oops. I dug my vegetable plot already. What is the problem with digging wet soil? I wanted to get a jump on it, because I am one of those gardeners that think I have plenty of time and then find my tomatoe plants crawling along the ground in July because I never got around to staking them up…

Time is at a premium for the gardener at this time of year! Linda Gilkeson is one of many experienced gardeners that believes digging your soil can degrade its structure and kill beneficial life contained within it (plant, animal and microbial), And it’s particularly harmful when the soil is wet. Here’s a decent article explaining:

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