April marks a significant transition in the gardening year, shifting the focus from planning to the tangible act of sowing seeds outdoors. This month offers the first opportunity to direct-sow seeds into the garden soil. The cool, moist conditions of early spring are perfectly suited for numerous hardy plants. Understanding which seeds to plant now allows gardeners to maximize their yield and extend the harvest window. Successful spring sowing hinges entirely on local climate conditions, making specific timing a localized decision.
Determining Your Local April Planting Window
The calendar date of April serves only as a general guideline, as successful planting depends on two variable factors: the Last Frost Date (LFD) and the temperature of the soil. The LFD is the average date the air temperature last dips to 32°F, determining when it is safe to transition frost-tender plants outdoors. For example, in colder regions, the LFD may fall in mid-May, meaning April is still a time for cool-weather planting. In milder regions, the LFD may have already passed, allowing for an earlier shift to warm-weather crops later in April.
Soil temperature is the more accurate metric, as it directly influences a seed’s ability to germinate and grow. Cool-season vegetables require a minimum soil temperature of 40°F to 45°F to sprout successfully. Planting seeds into cold soil below this range can lead to delayed germination, rot, or a weak start. Gardeners should use a soil thermometer inserted two inches deep to confirm conditions are appropriate for cool-season seeds.
Cool-Season Vegetables for Direct Sowing Outdoors
April is the prime month for sowing vegetables that thrive in cool soil and tolerate light spring frosts. These hardy crops benefit from an early start, allowing them to mature before the intense heat of summer causes them to bolt. Direct sowing is the preferred method, as many develop long taproots or dislike the disturbance of transplanting.
Root vegetables are ideal for April direct-sowing, as they need loose soil to develop properly. Carrots require a minimum soil temperature of about 45°F and should be sown shallowly, only about 1/4 inch deep. Radishes germinate quickly, providing a fast harvest in three to four weeks. Turnips and beets also tolerate these cool conditions. Radishes, turnips, and beets should all be sown about 1/2 inch deep.
Leafy greens and peas are equally suited to the cool soil of April. Spinach is one of the hardiest options, capable of germinating in soil temperatures as low as 35°F, and its seeds are sown at a shallow depth of 1/4 inch. Lettuce and kale seeds are also placed about 1/4 inch deep and benefit from spring moisture. Peas are a classic early-spring crop, germinating when the soil reaches 40°F. Their seeds are planted about one inch deep to support the vining growth.
While Brassicas like broccoli and cabbage are often planted as transplants in April, their seeds can also be sown directly early in the month. This approach is best reserved for regions with a long, cool spring, as the plants need significant time to form heads before summer heat arrives. The seeds should be planted about 1/4 inch deep. Starting these crops from seed in April is a race against the calendar to ensure maturity before high temperatures induce bolting.
Starting Warm-Weather Crops Indoors
April is the window for starting frost-sensitive, warm-weather vegetables indoors, giving them a head start. Plants like tomatoes, peppers, and eggplant require a long growing period, so they are typically started six to eight weeks before the Last Frost Date (LFD). This allows seedlings to develop a robust root system, making them strong enough to transplant outdoors after all danger of frost has passed.
Early starts of heat-loving vine crops, such as cucumbers, squash, and melons, can also be initiated indoors during late April. These crops grow rapidly, so they are typically started closer to the LFD, generally about two to four weeks prior. Starting them earlier risks them becoming root-bound and stressed before they can be safely moved outside.
Successful indoor seed starting requires maintaining specific environmental conditions. A seed-starting mix, rather than garden soil, provides a sterile, fine-textured medium for delicate roots. Heat mats are used to elevate the soil temperature to the ideal range of 60°F to 70°F for germination. Once seedlings emerge, they must receive intense light for up to 16 hours a day, often provided by grow lights positioned four to six inches above the foliage to prevent weak, elongated stems.
Annual Flowers and Hardy Herbs
April is an opportunity to sow seeds for hardy annual flowers and herbs that tolerate cooler temperatures and light frost. Direct sowing these seeds outdoors allows them to establish deep roots, resulting in a more robust plant. These flowers often bloom earlier and longer than those planted after the LFD.
Hardy annual flowers that can be sown directly include Poppies and Calendula, which thrive in spring conditions. Sweet Peas are another excellent choice for April sowing, preferring to establish root systems in cool soil before vigorous climbing growth begins. These seeds are typically planted at a depth of one to two times their diameter and kept consistently moist until germination.
Several popular herbs also fit the criteria for April direct-sowing. Cilantro and Dill are well-suited to cool spring conditions, as they are prone to bolting once the weather turns hot. Parsley, a hardy herb, also benefits from an early spring start. Planting these herbs in succession throughout April can ensure a continuous harvest before summer heat forces them to cease production.