April marks the transition from winter dormancy to active growth for gardeners in temperate climates. Lengthening daylight hours and warming soil temperatures signal the opportunity to begin outdoor planting. Successful planting in April requires considering local environmental conditions and the specific needs of various plant types. This guide provides a practical framework for maximizing your garden’s potential during this spring month.
Understanding Your Local Planting Window
The most important data for April planting is the average Last Frost Date (LFD) for your region. This date represents the point after which the probability of temperatures dropping to 32°F (0°C) or below significantly decreases. Local agricultural extension offices or reliable online tools provide this localized information using historical weather data.
Knowing the LFD divides the month into pre-frost and post-frost planting periods. Plants are classified as hardy, tolerating light frost and cool soil, or tender, suffering damage near freezing temperatures. Soil temperature is crucial for germination, as many seeds require sustained temperatures above 45°F (7°C) to sprout reliably. Planting sensitive varieties prematurely into cold, saturated soil often leads to poor germination, disease, and stunted growth.
Cool Season Vegetables for Direct Sowing
If your LFD is later in the spring, April is the optimal time to directly sow seeds for cool-season crops. These vegetables germinate best in soil temperatures ranging from 40°F to 60°F (4°C to 15°C) and will bolt (prematurely produce seeds) once summer heat arrives.
English peas are ideal for April sowing, requiring moisture and cooler soil to establish root systems. Plant them one to two inches deep, ensuring supports are ready for climbing varieties. Root vegetables, such as carrots and radishes, also benefit from early planting, allowing taproots to develop before warm soil causes cracking or bitterness. Radish seeds are sown a half-inch deep, while carrots are sown shallowly (about a quarter-inch deep) and thinned rigorously after germination.
Leafy greens, including spinach, kale, and lettuce, can be direct-sown now for a spring harvest. Spinach and kale are resilient to light frosts; their seeds can be planted about a half-inch deep or sown densely for baby greens. Heading lettuce varieties should be planted shallowly and thinned to eight to twelve inches apart. Sowing these vegetables in April ensures they mature before high heat stresses them, resulting in a more flavorful harvest.
Starting Tender Plants Indoors
April is the deadline for starting many warm-season crops indoors to ensure a timely harvest. Heat-loving plants, including tomatoes, peppers, and eggplant, have long maturity cycles and must be transplanted only after the danger of frost has passed. Starting seeds indoors provides a controlled environment, giving them a four to eight-week head start before moving outside.
Bell peppers and eggplant require up to eight weeks of indoor growth to reach transplant size, while some early tomato varieties need six weeks. Germination requires consistent warmth, ideally 75°F to 85°F (24°C to 29°C), often achieved using heat mats. Once sprouted, seedlings need twelve to sixteen hours of high-intensity light daily to prevent etiolation (becoming thin and weak).
South-facing windows rarely provide sufficient light, necessitating supplemental grow lights suspended a few inches above the foliage. April is also the time to start seeds for summer and winter squash, such as zucchini or pumpkins. Due to their rapid growth, these large seeds are typically started only three to four weeks before the LFD. These tender seedlings must remain protected until both the air and soil outside have warmed considerably.
Ornamental Flowers and Herbs
April offers opportunities for planting ornamentals and specific culinary herbs. Certain annual flowers and perennials have high cold tolerance, making them suitable for early direct sowing or transplanting. Hardy annuals like pansies, calendula, and bachelor buttons withstand light frost, and their seeds can be scattered onto prepared garden beds.
Perennials started indoors in late winter, such as columbine or delphinium, can be safely transplanted outside in April. They are adapted to cooler spring temperatures, allowing their root systems to establish before summer heat arrives. Ensure proper soil drainage, as heavy spring rains can saturate the ground, making poorly draining areas unsuitable for early transplants.
The timing for herbs varies based on hardiness. Mediterranean herbs like basil and oregano are sensitive to cold and should be started indoors now for later transplanting. However, cool-season herbs such as cilantro, parsley, and dill can be directly sown outside in April alongside leafy greens. These herbs germinate well in cooler soil and bolt (become bitter) if exposed to high temperatures, making an early start advantageous.