March Garden to-do List
Image by Jupiter Images
Sharon Hanna offers expert advice on what gardeners should be doing in March.
Indoors Start broccoli, cabbage, leeks, lettuce, parsley, tomatoes, cauliflower. Peppers are slow to sprout—and not that productive in many BC gardens. If you really want to grow peppers a heated greenhouse is helpful! Seed in the first week of March at the latest. Give them bottom heat and as much light as possible. Outdoors We often hear about not digging until "soil can be worked." What does this mean, exactly? Soil shouldn’t be clumped in muddy clods. A clue: self-sown seedlings of kale, arugula, mache will abound (weeds, too); chives poke up. If it’s been raining heavily, or soil looks and feels waterlogged, wait a week or two. Some gardeners prefer to interfere minimally with the soil—I am one of those. Creatures have been labouring long hours, layering the soil perfectly, like a lasagna, so I am loathe to plunge a shovel in. There are schools of gardening thought (Ruth Stout, for example) where gardening is done using this "barely scratching the surface" method, usually also piling on the mulch. If you are interested, check out Ruth Stout’s “no dig” method of gardening—also Esther Dean’s and others. Avoid using fresh manure and unripe compost in veggie gardens, as they will leach nutrients from plants. Soil is still too cool to plant carrots, chard, or beets. Wait until late April or until soil temperature is over 55F.
When the ground can be worked:
Direct-sow arugula, broad beans, mache, corn salad, kale, broccoli raab (rapini), dandelion greens (not real dandelions, but a type of chicory), Asian greens, radishes. Peas: soil is still cool, so use inoculant. It increases microbial activity around the seed and allows peas to sprout in cool soil. Give potatoes an early start: put one or two ‘seed’ potatoes per one-gallon black pot in a lofty slightly acidic soil mix—peat moss (if you use it) mixed with garden soil half and half is fine. Keep these in an unheated greenhouse or on the porch and plant out in April when soil ‘can be worked’!
Plant dormant shrubs and bare-root trees whenever you are able to dig the planting hole. As soon as forsythia and other early-spring bloomers are done flowering, prune them back. Hard! If forsythia has gone berserk, consider “massive renovation”—cut it right off at the base. It will grow back fine in a year or two. Use extra caution when pruning marginally hardy plants and vines even though the sun shines brightly. I’ll never forget losing my Clematis armandii when my dad cut it back radically in early March. It had been warm weather—so warm you could sit outdoors in the daytime in a t-shirt. However, after he pruned, temperatures dropped to -10 C at night and the vine died.
Lightly tread on Iris rhizomes if you’ve had lots of frost. Dig, clean up and divide bearded Iris now, removing brown/diseased-looking parts of rhizome and trim withered roots. Cut healthy sections with good roots on each. Leave half the rhizome exposed to encourage flowering. If your Siberian iris didn’t bloom much last year, it probably needs to be dug out and divided. This should be done every four years or so in order for the plants to flower. You can be relatively brutal with these tough plants. However, be gentle with your wonderful earthworms. They’ve been doing their job layering the soil and adding nutrients, and living in their little "family" groupings. It’s an old wives tale that you can cut a worm in half. Dig or divide any emerging perennials. As light levels increase, they’ll grow quickly, so don’t delay. For the cottage-garden look, replant perennial divisions in wiggly, uneven drifts, mimicking nature; avoid lining up plants like marching soldiers. Consider eventual plant height, placing taller plants towards the back. Well-advanced perennials like Doronicum (leopard’s bane), Pulmonaria (lungwort) and other early bloomers, should be left alone now. Divide them in late summer or fall. When replanting, add a modest amount of nutrients – SeaSoil, other amendments, and a very light sprinkling of balanced organic fertilizer. Scratch in shallowly around new divisions. Don’t forget to add water. Revive and rejuvenate perennials in containers – add organic material annually. Amend clematis and other flowering vines with organic material, especially if you are growing them in pots. Give all of these a light “welcome to spring” feed of kelp or fish-based fertilizer. Amend clematis and other flowering vines with a handful of 6-8-6 too, especially if you are growing them in pots. Clematis roots are shallow so cultivate minimally. If you didn’t do this in February, add a little bit of calcium carbonate—just a few tbsp—per plant, keeping it 6–8 inches from the plant and scratch in very lightly. Hopefully, you have already pruned back Type “C” varieties to their knees. If not, they’ve already budded out well up the stem and it seems a shame to cut them back now. See what happens (they’ll bloom much higher up) then make a note to remind yourself to prune earlier next season.
Prune back roses if you have not done this already. In warmer zones, this pruning is best done in February before too much leafy growth occurs, but it’s not too late now. Gently remove soil or mulch that has been mounded over the crown for winter protection. Amend with manure or compost. Don’t feed yet until active growth begins, and then go lightly, using organic fish or kelp-based liquid or granules.
If you like to feed your lawn, give it a first modest feeding this month. Consider using environmentally friendly organic lawn food this year, or remove part of your lawn to grow food in raised beds, or try making a lasagna garden right on top of part of your lawn in a sunny area. No digging involved at all—really! Remember, the more you feed your grass, the faster it will grow!
Around the Garden
If you are really keen, run kitchen waste through an old food processor or blender set aside for that purpose before you compost. Worms find it much easier to eat small pieces of food. Add a bag of clean animal manure—horse, steer, or chicken, if you like to do that, to speed up the process in your compost. Keep on top of annual weeds (how did they get so big, so fast?), and don’t let the first ones go to seed—less work later on. Toss them into the compost—”weeds” contain valuable nutrition, as they mine the soil and bring up nutrients to the top.
Seeds & Propagation
Avoid rushing to sow seedlings too early, indoors. You’ll have better results and less problems if you wait until light levels are higher outside. When temperatures warm, you can sow in an unheated greenhouse, on the porch, in a cold frame. You have to wait until outdoor temperatures and soil warms before you can plant your precious seedlings out. It is way too early to start basil! Basil is from Africa and loves hot weather. A common seed-sowing error: skimping on starter mix in pots, filling only halfway. Seeds sown low in the pot are vulnerable to fungal diseases and damping off especially if air circulation is poor. Seedlings should sit high in their pots. When watering seedlings:
- avoid doing in direct sun
- use room-temperature water
- allow water to sit in an open container overnight so chemicals can evaporate.
Young seedlings need hardly any water; keep soil surface on the dry side. If you have a tendency to overwater, try adding a thin layer of fine sand. Seedlings don’t need to be fertilized until they have one or two sets of true leaves. Even then, fertilize at quarter strength. Seedlings wilting at soil level may have succumbed to the dreaded damping off virus. They won’t recover, sadly. Anxious gardeners add more water thinking seedlings will revive. Overwatering may actually have contributed to the condition. Basil is particularly vulnerable—another reason to wait until May and conditions are more optimal. Create excellent air circulation by using a small fan. Though it’s tempting, try not to start more plants than you can handle or for which you can find a good home! Grow less and put more energy into making the plants healthy and strong.
On the coast, lightly trim back lavender when weather warms—it might not be in March! If night temperatures are below zero at night, don’t prune yet. In cooler zones, hold off. This beautifully scented woody shrub does not respond well to hard pruning and may actually perish as a result. Avoid cutting back more than 25 percent of any stem. If stems seem bare and scraggly towards the bottom: 1) leaves will eventually fill in, 2) you may have forgotten to prune lightly last year. Trim lightly and regularly.
Start houseplants on a regular but sparse feeding plan, using organic-based fish or kelp fertilizer. They’ll grow healthy and strong with fresh air and a bit of sunlight.
Many flower seeds may be sown in the greenhouse this month—check seed packages. Very hardy annuals may be direct-sown in zones 7 and 8: calendula, California poppies & bachelor buttons (beautiful together), other annual poppies, wildflower mixes, nasturtiums, clarkia, sweet peas.