March Gardening Tips
Note: Please note that all information on this page applies to the Portland Metro area, and may not be applicable for higher elevations or different climates.
Planting season has begun! Assuming your ground is workable, now is first planting time for most of us. If you have water-logged clay soil you might want to cover it with plastic or wait for a dry spell before digging, but otherwise start getting those hardy plants in the ground. The danger of frost is not past, so it is still time to protect tender plants (those that cannot survive a hard frost). This includes newly planted vegetables and annuals. Note that it is simply too early for truly warm season crops.
If you mulched your garden heavily before winter, you might consider removing part (not all) of it now. A thick layer of mulch can slow soil warming and delay plant growth. If you used compost as your mulch, it can be dug in unless this will significantly disturb root systems of neighboring plants. If you used bark or similar organic matter, it is best to compost it before digging it in. If you did not mulch before winter, this is a good time to add a light layer of compost to your soil. Remember that mulch should not be piled up against the trunk of a tree or shrub.
Slugs and cutworms can cause considerable damage during this time of year, so keep an eye out if you have susceptible crops such as lettuce and other greens. Aphids can seem to appear out of nowhere in March and can start doing damage on many crops and ornamentals. These pests can be controlled with appropriate baits or sprays, just be aware that they breed and spread fast.
There is plenty of color ready for you now that spring is arriving, though the full selection of summer bloomers are not quite here. Pansies have been with us all winter and are still great, but now add to the list: blooming bulbs, anemones, ranunculus, snapdragons, alyssum, and more. By the end of March we will have geraniums, fuchsias, and other hanging basket plants. As for new perennial availability, look for candytuft, rock cress, and creeping phlox; all are in bloom and ready for your garden. The evergreen perennials have been in full swing with good availability on hellebores, coral bells, rosemary, lavender, and more. Hellebores especially steal the show in February and March.
See all that new growth starting to form in your perennial beds? Now is the time to get out the old plant food. If you use granular foods, it is a great time to start regular applications.
If you prefer water-soluble fertilizers, you might consider waiting awhile or at least until periods of somewhat warm and dry weather. March is often an acceptable time for dividing and moving perennials. If you have not done so, remove dead matter on your perennials if you prefer a tidy look. Cut back any ornamental grasses that are dead looking and brown. Do not cut these to the soil line; leave a tuft to ensure better regrowth.
We are fully stocked with bulbs inside the store now, including begonias, lilies, dahlias, and many others. Get all those summer bloomers now and grow them yourself. This is significantly less expensive than buying grown plants later in the season.
Feel free to plant out most greens and cole crops (broccoli, cauliflower, etc.) but be ready with frost blanket for any extra cold nights. Many root crops can be planted now, including onions, potatoes, radishes, garlic, and shallots. When planting root crops, be sure the soil has a fair amount of organic matter, and few or no rocks. If you haven't already, peas can be started in March. Waiting too long can reduce the chance that you will get a good crop; peas like it cool. Unfortunately, it is not yet time to be planting most "fruiting" vegetables yet, such as tomatoes, peppers, or squash. Also, skip the basil outside; too early. Sorry. Such plants can be started in heated greenhouses, or possibly in the house.
If you do choose to start seeds in the house to get a jump on summer, March to April is often good timing. Most seed packets will say how many weeks before last frost the crop should be started indoors, so plan accordingly. Last frost timing can vary greatly here, with April 15th being about an average, and frost unlikely after May 15th. Here are a few cautions about seed starting indoors. Grow lights can help immensely, but often a bright south or possibly west window will do. Remember that most crops prefer full sun, and they won't be getting it. Also, if the time you were planning on placing the starts outside turns out to be unseasonably cold, you might have to delay the planting (remember any rainy Junes?) and the plants might get very leggy.
Now is a good time for a first lawn feeding, especially if you are using an organic granular fertilizer. If you prefer a synthetic food, make sure there is a spell of mostly dry weather ahead to avoid runoff, though you do want to irrigate once after application. If you have not done so in the last year, you can apply some horticultural lime.
April is often one of the best times to add more seed to your lawn, but March can work if the weather is fair. This is recommended for thin or patchy lawns. If you have a thick layer of thatch, you can rake it out now. Moss control products can be applied now if you have not done so already. Watch for the first appearance of weeds; everyone that you remove before it flowers is a generation of them that won't be growing later. Note that most herbicides do not work in cool weather, so I am talking about hand weeding.
March marks the beginning of tree and shrub planting season, and we have a great availability. Roses and fruits especially are fully stocked at both of our locations. As the plants flush out their new growth, fertilizing can be started on both recent and older plantings. Roses can be pruned in March if they were not done in February; the sooner the better at this point. If your do not want your pines to get bigger, prune the candles, or new growth off. Hedges can be sheared now if they are overgrown after last year.
Early flowering shrubs can be pruned after the flowers have faded if are just controlling their size. Any pruning of trees should probably have already be done, or delayed until summer in some cases. Start watching for the first signs of infection on new growth of disease-susceptible plants. Once the leaves have formed it is too late to dormant spray, but there are in-season pesticides that can help an emerging problem. It is easier to control a problem as it develops than once it is covering your plant.
Spring is the best time for repotting of houseplants, and it might now be time to pot up any of yours that really need it. Symptoms of needing a bigger pot include drying out more rapidly than usual or just seeming way too big for the pot. Always use fresh potting soil and loosen the root ball if it is wound up. When going up in pot size, only go one to two inches in depth and/or width. Always water your plants after repotting. Keep in mind that overwatering can still be a problem, as the days are often still quite cloudy. This is especially true of any recently up-potted plants. If you have plants that are particularly sensitive to overwatering then wait until later in spring for repotting.
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