March 22, 2023: Do (and not do) list; Marvelous mulch

From Linda Gilkeson:

With the first days of spring officially here and after a couple of warm, sunny days this week, things are picking up in the garden. The first bumble bees, butterflies and hover flies are visiting crocus and my red flowering currants are bursting with bright colour (to the delight of hummingbirds). Looking back my March 20, 2022 message, I see that the list of resources for coastal gardeners still looks useful, especially for new gardeners. If that interests you, read it at: Linda Gilkeson || West Coast Gardening || Gardening Tips. There is also info in that message on how to grow more in the same space, so there is no need to repeat it here….

Here are some things to do/not do over the next few weeks:
-By the end of the month, dig up root crops still in the garden and store them in the refrigerator. As the weather warms they start to grow, using up sugars stored in the roots to grow a flower stalk with a corresponding loss of flavor and quality.
-Don’t clear away damaged winter vegetable plants yet: Leafy greens often grow all new leaves from the roots and provide a good spring crop (even plants that look dead right now may make a comeback); bald stalks of kale often send out side shoots with new leaves.
-Don’t get rid of Brussels sprout plants even if you have picked all the sprouts: The plants will grow a new set of very tasty and tender shoots where the sprouts were.
-Plant peas outdoors and a few potatoes, sow seeds of annuals: lettuce, spinach, radishes, cilantro, dill. Scatter the seeds on the soil surface, then press them into the soil or cover with a very thin sprinkling of soil. They will germinate when they feel like it (but usually come up surprisingly early). Such early plantings often work out, but just be prepared to sow again if they don’t.
-Plant strawberries, fruit trees, berry bushes, asparagus any time.
-If you are starting seeds indoors, sow tomatoes, peppers, early cabbage, cauliflower, broccoli in the next week or two. Starting peas indoors and planting them out after 2-3 weeks give much quicker results than sowing seeds directly in the garden.
-If you are growing seedlings indoors, try to expose them to a couple of hours of sunshine outdoors whenever we have a warm, sunny day. They will be healthier for the experience of bright, full sun!

More on mulches: I often mention mulching, but thought I would focus on that this month in response to some recent questions. Mulching is the key to low maintenance, high success gardening and a practice that provides a multitude of benefits. Clean cultivated gardens, with bare soil between the plants, can still be seen in outdated gardening books and was the way I learned to garden (back when the earth was cooling….). It is how field-scale vegetable are often grown for a variety of reasons. But home gardens are not mini-farms and the logistics of getting enough mulch for a garden is much easier than trying to mulch a farm field (growers use cover cropping and other practices to do what mulches do in a home garden).

By mulch, I mean organic material, such as fallen leaves, straw, coarse compost, crop waste, cut or pulled weeds, shredded paper and other biodegradable materials, including wood chips. The latter are excellent for perennial trees and shrubs, but not vegetable gardens where they can get mixed into the soil and end up depleting the soil of nitrogen needed by plants. Organic mulches insulate the soil, preventing freezing and damage to crowns of plants overwintering outdoors. Mulches also prevent soils from baking in summer heat and damaging roots of vegetables (young seedlings have roots close to the surface and are especially vulnerable to heat waves). Mulches conserve irrigation water by reducing the evaporation of water from the soil, which can be especially significant while plants are small. Later, as leaves of full-grown plants shade the soil, up to 85% of the moisture leaving the soil is removed via plants through the process of transpiration, but it is still worth mulching to conserve the estimated 15% of water that evaporates directly. Because mulches shade the soil, they prevent weeds from germinating (many seeds need exposure to light to germinate) and they kill seedlings that do germinate by blocking the light. As surface mulches decompose through the action of earthworms, insects, and the myriad of soil microbes, they provide nutrients for plants. Surface mulches build soil organic matter faster than you can by digging in compost. As if that wasn’t enough, mulches make an attractive habitat for ground beetles and rove beetles, which are predators of slugs, root weevil larvae, root maggots, etc.

On that note, some of you are wondering if mulches increase slug damage. I don’t think so, especially since mulches provide good habitat for slug predators. It my experience, slug damage seems to be worse in beds without mulches. Slugs eat decaying vegetable matter as well as tender plants, so when there is no mulch, they only have plants to eat. However, there is a time to remove mulch from garden beds and that’s when you want to sow seeds or plant small seedlings. Rake mulch off the bed to allow the soil to warm up and dry out for spring seeding. Once seedlings have grown several inches high, start pushing mulch back between the little plants, adding more as plants grow and especially when a heat wave is forecast.

Plastic mulch? landscape fabric (“geotextiles”)?: Although plastic and paper mulches are used in agricultural fields to control weeds in veggie crops, there is no need to buy such products for a home garden because organic mulches do that weeding job and so much more. Landscape fabric is synthetic fabric that never biodegrades. It looks neat for a couple of years, but eventually suffocates plant roots and soil organisms that should be present in a healthy soil. The pores of the fabric clog with debris so less and less water penetrates and the essential exchange of oxygen and carbon dioxide from the soil is blocked. Seeds of grasses and other weeds eventually root on top of the fabric so weeding chores resume. Landscape fabric is most often used around landscape plants, but I have seen people try to use it under berry bushes and fruit trees. Eventually, the suffering plants may send out roots on top of the fabric in order to survive. If this mulch is used for a few months as a temporary weed control while perennial plants are becoming established, then removed and replaced with an organic mulch, little harm is done—but it is far better not to use it around plants at all.

Similar concerns apply for cardboard: At least cardboard is biodegradable and will disintegrate after a few years. The best use for cardboard is over the winter months to kill sod or weedy patches in preparation for making an area into a new garden. Cardboard stops light from reaching the plants below, which is what kills them. It also prevents oxygen and water from reaching the soil below, which is why it shouldn’t be left in place longer than the few months needed to suffocate the sod (winter is an ideal time to do this because the soil doesn’t dry out and soil organisms are dormant anyway). Using cardboard (or thick newspaper layers) to kill sod is much less work than stripping off the sod and allows you to keep the topsoil and organic matter in the sod in the garden. If you have built raised garden beds on top of a cardboard layer (a commonly recommended, but very faulty practice), do what you can to destroy that barrier. There is no need to dig up the bed, but do drive a pitchfork or garden fork into the soil deep enough to rip holes in the cardboard and hasten its decomposition.

Beware those dang cutworms: Getting fatter every day are climbing cutworms, which are caterpillars of the Large Yellow Underwing Moth. If you have overwintered vegetables, it would be well worth spending a few minutes with a flashlight after dark looking for them, especially on lettuce, spinach and chard, because they have now big enough to eat a lot of leaf area overnight. If you are not sure what to look for, see: Linda Gilkeson | West Coast Gardening | West Coast Gardening: Natural Insect, Weed and Disease Control Cutworms will be at their most voracious during April, but their feeding stops suddenly in late April to early May when become pupae (from which the adult moths emerge later on). My little dog is surprisingly good at finding cutworms while we’re on a bedtime stroll around the yard. That, along with her skill in finding and fetching gardening gloves, is making her a useful garden helper!

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.