- In late winter, prune deciduous trees, when the structure of the tree is not hidden by leaf cover.
- Shrubs grown primarily for their foliage rather than flowers can be pruned when bare of leaves. To retain a natural appearance, remove the oldest two-four branches at their base in addition to dead or branches that cross and rub.
Do not prune early spring blooming shrubs until after they have bloomed. These include forsythia, lilac, azalea, clove currant, quince, magnolia, or early blooming spirea. Unsure of your bloom time? Look for flower buds that set last fall or check reliable sources.
- Tree and shrub pruning is still timely this month.
- Check indoor plants for insects.
- Remove the spent flowers of bulbs such as amaryllis, but don’t remove their green stems until they brown and wither.
Gardens and trees start to awaken this month as the air temperature rises and the soil warms. Some spring tasks have a wider window for completion, and others a more temperature-sensitive schedule. Such tasks such as pruning are better completed while it is cooler before leaf-break, and others such as sowing cool weather crops are more successful when we fine-tune our planting date to soil temperature.
Though the beginning of the growing season varies each year, start with these average temperatures in March in the Wenatchee area and fine-tune for this particular year and your location. Chelan and Leavenworth areas will be later:
- March average high is 55° and average low is 31°
- March average soil temperature at 6 inches is 46°F
- Trees begin to awaken when the soil temperature at 6 inches is 43°F
- Last reliable frost- May 1-10. It may be earlier.
While it is still cool, its time to prune.
- Tea and floribunda roses were pruned back to about 36 inches last winter to protect stalks from breakage during heavy snow fall. Now its time to prune them to their spring height of 12- 24 inches. Trim to an outside-facing bud, making the cut approximately one-quarter of an inch above the bud and at a downward angle. Remove at the ground level any broken, dead, or crossing canes.
- Prune fruit trees.
- Forsythia bloom heralds Spring in our area. Use this bloom time as a reminder to apply pre-emergent to lawns to prevent germination of crabgrass, purslane, oxalis, and spotted spurge.
- Perennials are beginning to emerge. Remove last year’s dead growth before new leaves emerge. Winter mulch can remain until after all danger of frost.
- Cut back ornamental grasses to 6-12 inches.
- If the soil warms in a usual Spring, potatoes are planted Easter weekend.
- Apply dormant spray to fruit trees when buds begin to green. The spray smothers insect eggs and larva.
- Many varieties of heather are still in bloom this month. When flowers are spent, trim the stems back to green growth to keep the plant bushy. Avoid cutting into brown woody growth, as it may not regenerate.
- Early this month, spray for peach twig borer and green peach aphid.
First application when flower buds show pink.
Second application after flower petals fall (known as “at shuck”). Apply only as directed per the schedule and the manufacturer’s instructions.
Review sprays at WSU Hortsense
- Spray for adelgid on Douglas fir at the first signs of growth. Hose tree off well with water prior to spraying.
- Spray home garden cherry trees – read spray schedule
- Spray home garden apple trees – read spray schedule
- Last frost usually occurs May 1-10 in the Wenatchee Valley. A few days later in Chelan, and about a week later in Leavenworth.
- Plant dahlias. Read more about them.
- Wait until the end of April to mid-May to plant tender annuals and vegetables
- Harden off annuals and vegetables raised indoors before planting them in their summer location. Acclimate them slowly to the brighter light and wind of outdoors. During the day, move them outside and at night return them to a sheltered location, or indoors if frost threatens. Move them first outside into shade for several hours. Extend the time over a few days. Then over several days increase their sun exposure. This process may take 7-10 days. Read more about it.
- When you start irrigating, water deeply and not as frequently to soak roots and encourage deep growth, instead of frequently and not as deeply. Water early in the morning. For plants on drip irrigation, remember that roots of established plants extend out from the trunk or stem 2-3 times the height of the plant.
- When the soil temperature reaches 55°F, warm weather plants and seeds can be planted directly into the garden. Mother’s Day is a good rule of thumb.
- When cherries start to turn from green to light yellow, begin your spray program using approved spray and timing to control cherry fruit fly.
- Prune early-blooming shrubs like forsythia and lilacs soon after they finish blooming and before they set new growth, which will carry next year’s bloom. Deadhead primroses.
- Fertilize roses in early May.
- Install supports on peonies.
- Start new lawns or over-seed while the weather is cool.
- Fertilize container plants every two-three weeks.
- Increase water irrigation as the temperature rises and the humidity drops.
- Lawns use more water June 15-August 15. Watch for a color change to a blue cast to indicate when to water. Water deeply. To help estimate when the lawn has received one inch of water, set several tuna fish cans around the lawn and when they are full, turn off the irrigation. When the water has evaporated and the can is empty, its time to irrigate again. Water deeply to encourage deep roots and less frequently, versus frequently and less deeply.
- Leave grass clippings on the lawn. As they decompose, they give a small shot of nitrogen to fertilize the grass.
- Sharpen mower blades for clean cuts.
- Set mower height to 2.5 – 3 inches. Longer grass shades the soil, encourages deeper roots and higher drought tolerance, and reduces weeds. Cut no more than 1/3 of the grass height each mowing.
- Pinch off faded blooms to encourage new flowers.
- Pinch chrysanthemums back every 6 inches of growth until July 4. They will be bushier and have more blossoms this Fall.
- Fertilize roses after the first blooms.
- Begin training indeterminate tomato plants. Staked tomatoes produce earlier than those sprawling on the ground. Pinching out suckers that sprout between the main stem and the leaves directs growth to the main stem and fruits. While this reduces yield, it produces larger fruit. Do not remove leaves that shade fruit and protect against sun scald. Read more about tomato culture.
- Continue to pinch off faded blooms to encourage new flowers on plants that rebloom.
- Tomatoes with black soft bottoms have blossom-end rot. It is caused by a calcium deficiency in the plant and is aggravated by fluctuating soil moisture. Apply a mulch to help maintain an even soil moisture. Tomatoes need 1 inch of water per week. Do not overwater, which can stimulate heavy leaf growth and cause blossoms to drop.
- Good watering methods help plants flourish. Check plants frequently and water long enough to get water to the root zone. Avoid overwatering and saturating the soil, which drowns the plant and encourages root rot.
- If fruit set seems low, “tickle” tomato blossoms and cross pollinate male and female squash family blossoms.
- Apply the last rose fertilizer by mid- August.
- Fertilize strawberries about August 15 for a good crop next year.
- Do not fertilize trees or shrubs with nitrogen, as it will encourage fresh growth that may not mature sufficiently to withstand winter temperatures.
- To encourage green tomatoes to ripen, pinch off the growing tips of tomato plants 30 days before the first frost. Expect frost by mid-October in the Wenatchee Valley, so pinch by September 15, and sooner in colder areas.
- Early to mid-September is a good time to seed new lawns.
- Cooler temperatures make this a good month to plant trees, shrubs and perennials. Their roots grow well and establish in the still-warm soil for a fast start next Spring.
- Spring-blooming bulbs can be planted this month.
- Taper off on the frequency of watering as temperatures cool.
- First frost sometimes occurs at the end of this month in the Chelan and Leavenworth areas.
- Start to transition outdoor plants that will come indoors for the winter. Pot up plants and move potted plants into shade to transition to lower indoor light. Before bringing plants indoors, wash leaves top and bottom to remove insects.
- When all your garden is harvested, rototill or work in compost or leaves to enrich it for next summer. They will continue to break down and encorporate into the soil on warm days.
- After the first frost, mow lawns a final time, at a height of 1.5 to 2 inches.
- Dig and prepare for winter storage tender bulbs, corms and tubers such as dahlias, cannas, gladiolas.
- Remove dead plants from the garden, and make lists of plants to add for next year.
- Vegetables will ripen slowly or not at all in shorter days and night-time temps near 43°. Harvest veggies that have begun to color and finish ripening them inside.
- Lavender has finished its second bloom of the year. Cut back to green growth to maintain a bushy and shapely plant.
- Got leaves? Put them to work.
- Mulch-mow them with your lawnmower and leave them on your lawn. The small pieces will break down over the winter and early spring and enrich the soil with nutrients, producing a better lawn.
- Mulch plants and trees with whole or ground leaves for winter protection.
- Compost the leaves for later use. Shredded leaves will compost faster than whole.
- Work the leaves into the garden bed this fall. In the spring, mix the soil again, or plant right into it.
- If soil is dry, water shrubs and trees to ensure they enter winter with adequate moisture.
- Snow is a good insulation blank for shrubs and perennials when it gently fills the voids between ground and branches. Mound light snow shoveled from an unsalted walk or driveway, taking care to distribute it through the shrub. Gently knock heavy snow from branches, which may bend or break fragile branches.
- Knock snow from low growing Japanese maple branches.
- The south side of tree trunks that have smooth bark are exposed to a freeze-thaw cycle induced by warm sun and glare off snow warming the bark. Protect young trees each year from sun scald until they grow rough, thicker bark that insulates the tree tissue. Options include shading the trunk with a board posted inches from the trunk; a flexible tube split lengthwise loosely encircling the trunk; light colored tree wrap. Remove all these options in the spring before the last frost. Light colored paint is another, longer lasting alternative.