April acts as the major transition month for Oregon gardeners, marking the shift from winter preparation to active planting. This time of year demands a localized approach, as the state’s massive geographical diversity means planting windows vary widely. A gardener west of the Cascade Mountains will face a completely different schedule than one in the high desert of Eastern Oregon. Understanding these regional differences is necessary to successfully move forward with spring sowing and transplanting.
Navigating Oregon’s Regional Planting Differences
Oregon is not a single planting zone, and April’s weather can be dramatically different depending on your location. The Willamette Valley and Coastal regions generally experience milder, wetter conditions, with average last frost dates often falling around mid-April. By contrast, areas east of the Cascades, such as Bend or Klamath Falls, face a much shorter season where the average last frost date can be as late as June. The “last expected frost date” is the primary factor dictating when it is safe to plant outdoors. Planting cool-season crops too early risks seed rot in wet, cold soil, so using a soil thermometer to confirm adequate warmth remains a more reliable guide than the calendar alone.
Cool-Season Crops for Direct Sowing Outdoors
April is the time to sow cool-season vegetables directly into the garden bed across most of Oregon, provided the soil is workable and not excessively saturated. Root vegetables, like carrots, radishes, and beets, thrive when sown directly, as they do not transplant well once established. For successful germination, the soil temperature should ideally register a consistent 40°F to 50°F, which is sufficient for hardy seeds like spinach and lettuce. Peas, kale, and Swiss chard are also excellent choices for direct sowing now. To ensure a continuous harvest, use “succession planting,” where small batches of seeds are sown every two to three weeks instead of planting the entire crop at once.
Transplanting Hardened Seedlings
In April, many gardeners move established, cold-tolerant seedlings, known as “starts,” that were previously grown indoors or purchased from a nursery, into the garden. This action is distinct from direct sowing and provides a head start on the growing season. Hardy brassicas, such as cabbage, broccoli, and cauliflower, are generally ready to be transplanted once they have developed several true leaves. Onion sets or small onion starts can also be planted now, positioning the bulb base just below the soil surface. Before planting, these starts must undergo a process called “hardening off,” which gradually acclimates them to outdoor conditions over seven to ten days. Young transplants remain susceptible to a sudden, sharp cold snap, so protecting them with tools like floating row covers or individual cloches can shield them from late-season frost damage.
Starting Warm-Season Crops Indoors
While the focus in April is on cool-season planting outdoors, the month is also a crucial period for starting warm-season crops indoors to prepare for summer. These heat-loving plants, like tomatoes, peppers, and eggplant, require a long growing season that Oregon’s climate generally cannot provide without a head start. Starting these seeds now, about six to eight weeks before the last expected frost date, ensures they will be mature enough to produce fruit after transplanting. These seeds need consistent warmth to germinate, ideally around 75°F, which is often achieved using a specialized heat mat beneath the seed trays. Once the seedlings emerge, they must be placed under strong grow lights for up to 14 to 16 hours daily to prevent them from becoming spindly.