Start onion/leek/celeriac seeds early in the month. Consider getting a heated germination mat. After the seeds germinate, take the plants off the mat and place about 4 inches below hang fluorescent or LED lights.
Start pepper, eggplant, and parsley seeds late in the month if you are in zone 6 or a warm microclimate of zone 5 (otherwise, early April). Soak parsley seeds in lukewarm water for a few hours first. Use the germination mat. Move to the light setup as soon as the seeds sprout.
If you have overwintered vegetable plants in a cold frame, make sure they don’t get overheated. If there are root veggies in the garden, dig them up as soon as you can before they resume growth or rodents get to them. Harvest overwintered leaf veggies (FEDCO Seeds has a great list of extra-hardy veggies that can be wintered over with the help of a cold frame or low tunnels or mulch.) Egyptian onion, also known as perennial or walking onion, needs no winter protection and provides an early harvest.
It’s time to start pruning fruit trees (except peaches) and grapes, before they leaf out. If you grow fall raspberries, and prefer to get the large crop in late summer and fall, prune all the canes down to the ground. ‘Polana’ is a great variety that fruits for over two months starting in mid-August. I avoid ‘Heritage’ due to late fruiting and susceptibility to Phytophthora root rot.
Observe where the snow melts first. This is your warmest microclimate. Consider putting your earliest spring bloomers there, such as snowdrops, winter aconites, and hellebores. Also, keep track of where the snow lingers longest. This is your coolest microclimate. When designing your landscape, consider this site for plants that tend to sprout too early and get damaged by late spring frosts. By mulching heavily and siting them in a cooler spot, they will stay dormant later and hopefully avoid such damage.
Watch out for water that accumulates on top of frozen ground. Consider covering sensitive alpines with a bucket or plastic box to prevent this. Water puddles can kill evenwinter-hardy plants such as purple poppy-mallow. Plant them on a slope to allow the water to drain away.
Winter is a great time to plan garden improvements because the architecture of your design is most apparent then. Take a photo of an area of your garden, and print it out on 81/2” x 11” paper. Tape a sheet of tracing paper over the photo and, with a pencil, sketch shapes and sizes that you might like to add to the picture. Sketch circles and sweeping lines of various lengths for shrubs and grasses. Use a stick and ball to represent flowering perennials. Is there a view you would like to maximize or hide? Use colored pencils to enhance your design.
Now is also a good time to evaluate and prune your ornamental trees and shrubs, except for species that are considered ‘bleeders’. Maples, birch, yellowwood, magnolia, linden, willow, and nut trees are just a few trees that should be pruned a little later, after the sap is finished running.
This is a good time to repot houseplants and resume fertilizing lightly. Look for problems such as insects. Leggy plants such as angel wing begonias can be pruned and the cuttings rooted.
Start tomato, broccoli, cabbage, and basil seeds indoors in mid-month (if you will have enough space under your fluorescent lights). Start fava beans in individual cells or pots late in March or early in April, depending on your microclimate. This is a bean that tolerates light frosts, so plant the seedlings outside later in the month, to get production before hot weather.
In late April, move pepper, eggplant, and basil seedlings to individual pots indoors. Consider applying black plastic or IRT (infrared transmitting) mulch to warm up the soil in the veggie garden where you want to plant heat-loving crops.
If spring weather permits, direct-seed cold-tolerant veggies such as peas, spinach, lettuce, radishes and carrots around midmonth.
Finish pruning fruit trees (except peaches) and grapes before they leaf out. Prune berry plants per recommendations. Consider applying row cover on strawberry plantings. Fertilize blueberries with an acid fertilizer such as ammonium sulfate (NOT aluminum sulfate) and/or apply elemental sulfur to keep the pH acid enough.
Protect early-sprouters from late spring frosts. Candidates for protection include the true lilies, Japanese painted fern fiddleheads, Kirengeshoma species, and crown imperial, all of which have been zapped one time or another in my zone 5 frostpocket location. You can use the same covers that you employ to protect your tomato plants in fall: old sheets and blankets that are not too heavy, cardboard boxes, or upside-down buckets. Avoid using sheet plastic and tarps. Do not rush to cut off last year’s foliage as it does protect the crown and emerging sprouts.
Early April is a good time to divide Solomon Seal before the stems elongate, and bloodroot before it sprouts. Later in the month, it may be time to remove last year’s stalks from mums, and divide the clumps if needed. Also, it’s a good time to divide many hardy perennials such as phlox, Siberian iris, Hosta, daylilies, asters, Helenium, Boltonia, Heliopsis, Shasta daisy, and so on. Bearded irises may be divided, but they probably won’t bloom this year. Lavender, culinary sage, Russian sage, and butterfly bush can have dead wood trimmed off late in the month, when winter damage and live buds can be distinguished.
Protect crocuses and tulips from animal damage. Crocuses are particularly vulnerable because a new corm needs to be formed each year; they do not have persistent true bulbs like tulips. A mulch of pea gravel helps to discourage digging, and then repellent sprays are needed once they sprout. A deer fence helps, but I suspect rabbits may also browse on the foliage.
If the spring is dry, and you have plantings that receive salty runoff, water them heavily to flush the salt down below the root zone. Prune off branches damaged by salt spray, and make a mental note to install a burlap screen to prevent salt damage next winter.
Use your germination heat mat for getting heat-loving tropical ‘bulbs’ such as caladiums started. Use shallow pots until they sprout. Depending on your microclimate, you may need to pot them up again before they can be safely planted outside. Other tender ‘bulbs’ such as dahlias and cannas can be potted up early, but should grow at normal indoor room temperature.
— Pat Curran and the Tompkins County Master Gardeners