April is a time of transition in the vegetable garden. Weather extremes from snow flurries to hot weather can occur in the Northern Hemisphere. In cold-winter regions, spring weather may be weeks away. In warm-winter regions, the last frost may already have passed.
When the lilacs bloom in your area, the time will be right to sow seeds directly in the vegetable garden.
The timing of planting is important in the vegetable garden. Frost and cool weather can harm warm-weather crops sown or transplanted out too soon. But cool-weather crops can thrive where there is still the threat of frost.
To get the most out of your vegetable garden, successive plantings of crops are a way to extend the season. Plant leafy greens and root crops as early as possible and then plant succession crops every week to 10 days. Quick-maturing crops are best for successive planting: lettuce, radishes, spinach, chard, peas, beets, and carrots in cool weather, and later in warm weather string beans and sweet corn.
Warm-weather crops like tomatoes, peppers, and eggplant can be started indoors now and transplanted into the garden after the last frost.
Ready your garden for the growing season by preparing planting beds during April.
Soil Preparation in Warm- and Cold-Winter Regions
- Cover your planting beds with clear or black plastic sheeting for a week to 10 days to warm the soil. When the soil is warm and dry, fork over the vegetable garden; dig in cover crops; remove weeds; rake soil to a fine tilth; spread compost. Apply aged manure and compost as needed. You can also place cloches in position to warm the soil. Prepare celery and potato trenches by adding a layer of well-rotted manure or garden compost to the trench area.
- Turn the compost pile when it thaws. Begin a new compost pile during the spring if you don’t already have one. Add dry leaves, grass, and non-fatty kitchen scraps to the pile.
- Remove winter mulch from around fruit trees, vines, and perennial vegetables when they flower or begin to sprout new growth.
Warm Region Vegetable Garden Checklist for April
If you live in USDA Plant Hardiness Zones 7-11, here is a vegetable gardening checklist for April.
(In the United States, USDA Zones 10 and 9 include the Gulf Coast and parts of the South Atlantic states, the Pacific Southwest—mainly Southern California, and parts of the Desert states. Temperature lows in the coldest of these regions can drop to 20°F (-7°C). In Europe, parts of Spain, Italy, and France and parts of countries bordering the Mediterranean Sea are in Zones 10 and 9. USDA Zone 8 includes the Mid-South, Pacific Norwest states and parts of Northern California. Zone 7 includes parts of the Northeast, Mid-Atlantic region, and eastern sections of the Northwest. Temperature lows in the coldest of these regions can drop as low as 0°F (-18°C). Much of the United Kingdom, France and parts of Spain are in Zone 8. The western regions of Germany are in Zone 7.)
Vegetable Planting in Warm Regions
- Sow in a cold frame, plastic tunnel, or beneath cloches in areas where frost may still come. Use horticultural fleece or floating cloches for early corps already in the garden if you don’t have conventional cloches.
- Direct sow hardy and half-hardy, cold-tolerant vegetables and herbs now: cabbage family members, leafy greens, and root crops: carrots, beets, cabbage, broccoli, Brussels sprouts, celery, chard, endive, parsnip, potatoes, spinach, and turnips.
- Before planting out cool-weather crops started indoors, harden off young plants from winter sowings–broccoli, cauliflower, kohlrabi, leeks, onions, lettuce, peas, and broad beans. Harden off plants by reducing the water supply or temperature.
- Make successive sowing at 10 to 14 day intervals of beets, carrots, lettuce, turnips, runner beans, green beans, endive, radishes, and kohlrabi.
- Direct sow tender warm-weather crops when the danger of frost is past and the weather is mild–plant out pole and bush snap and Lima beans, eggplants, pepper plants, casaba, celery, corn, okra, salsify, squash, cucumbers, cantaloupe, watermelons, Chinese cabbage, and black-eyed peas. Plant potatoes.
- By the end of the month, you can plant outdoor tomatoes, and tie them gently, but firmly, to stakes to secure them.
- Support young peas with sticks or netting. For sweet corn, several short rows in a rectangle will pollinate and be more successful than a few long rows.
- Celery should be fed about 3 weeks after plants are set out. Keep celery moist by regular irrigation. Black heart celery disease is caused by alternate drying and wetting of soil.
- Pinch out broad bean growing tips to encourage good pod set and deter attack from aphids.
- Stop picking asparagus so that the plants do not exhaust themselves. Prepare asparagus beds and plant asparagus crowns. In the northern regions, the first asparagus are starting to appear; cut the stems when they are 4-6 inches high.
- Remove rhubarb flowers as soon as they appear, before they rob the plants of food and energy.
- Begin to thin out overcrowded vegetable seedlings. Earth up potatoes as they grow. Cover seedlings and warm-weather crops with horticultural fleece if night frost is forecast.
- Feed seedlings with manure or compost tea after planting. Soak compost or well-rotted manure in water. You can use the resulting “tea” as a liquid fertilizer. Celery should be fed about 3 weeks after plants are set out. Keep celery moist by regular irrigation. Black heart celery disease is caused by alternate drying and wetting of soil.
- Water garden if weather is dry. Weed as needed. Turn compost pile.
- Watch for pests and signs of disease. Watch out for aphids on broad beans and root flies on cabbages, carrots, and onions. Pinch out the tips on broad beans to encourage good pod set and to deter attack from aphids. Remove rhubarb flowers as soon as they appear, before they rob the plants of food and energy. Water garden if weather is dry. Weed as needed. Turn compost pile.
Herb Garden in Warm Regions
- Sow seed or set out transplants of bay, hyssop, lavender, mint, rosemary, rue, and sage. Make further sowings of dill, fennel, parsley, and pot marjoram. Sow basil under glass. Propagate thyme by layering creeping stems and severing them when the roots have developed.
Fruit Trees and Berries in Warm Regions
- Set out strawberry bare-roots or seedlings. Remove flowers from newly planted strawberries to prevent fruiting in their first year. Pinch off runners on new strawberry plants. Put cloches over strawberries in frosty regions if you want an early corp. Allow access for bees. Cover berries with netting to keep away birds.
- Tie new canes of blackberries and hybrid berries to support wires. Allow a maximum of eight canes per plant. Summer-prune gooseberries by cutting back side shoots to five leaves. Fasten grape stems to training wires.
- Thin new fruit on citrus, apple, and peach trees. Thin heavy-cropping nectarines and peaches when fruit is ½ in (1-1.5 cm) in diameter. Protect open flowers from frost damage by draping muslin or horticultural fleece over trees at night. Mist open peach flowers with a fine spray to help the setting of fruit.
- Prune fruit trees cutting out crossing branches. On fan-trained apples, cherries, peaches, and plums, remove branches growing towards or away from the wall.
- Check for pests and diseases. Watch for signs of fire blight; prune affected branches and dispose of them. Watch for borers and caterpillars on trees. Hang coddling moth traps on apple trees. Spray against apple scab, mildew, and aphids.
- Spray against pests and disease when the buds burst or after the flower petals fall, but never on open flowers. Fruit trees and bushes should not be sprayed with insecticides while the flowers are open or the bees are working. Use sprays at dusk to avoid harming pollinating insects.
- Check tree ties on newly planted trees. Water newly planted trees and bushes during prolonged dry weather.
- Protect open flowers from frost damage by draping muslin or horticultural fleece over trees at night.
Greenhouse and Cold Frame in Warm Regions
- Plant greenhouse tomato plants in large pots, or plant them in grow bags.
- Water and feed greenhouse tomatoes, cucumbers and peppers, never letting the soil dry out.
- Attach slings or nets to melons as they swell.
- Continue to remove side shoots from tomatoes.
- Use biological pest control for greenhouse pests such as greenhouse whiteflies and spider mites.
- Ventilate the greenhouse and cold frame on mild days.
Cool and Cold Region Vegetable Garden Checklist for April
In cool- and cold-winter regions, the danger of freezing weather and frost continues through April in USDA Plant Hardiness Zones 6, 5, 4, and 3. Here is a checklist of things to do in the vegetable garden in cool and cold regions during April in the Northern Hemisphere:
(USDA Zones 6, 5, 4, and 3 are the most northern and coldest winter regions of the United States the northern parts of the Rocky Mountains, northern Plains and Midwest States and the northern regions of the Northeast and into Canada. Temperature lows in the coldest of these regions can drop as low as -40°F (-40°C). Eastern Europe is largely in Zone 6 and Zone 5.)
Cold Frame and Greenhouse Tasks in Cold and Cool Regions
- In northern regions, remove heavy mulch from around plants overwintered in the cold frame.
- Open the frame when temperatures are above freezing.
- Hardy and half-hardy vegetable starts sown last month indoors should be ready for the cold frame now.
- Sow cool-weather crops in the frame or beneath a plastic tunnel or cloches. Broccoli, cabbage, cauliflower, lettuce, peas, radishes, and spinach will grow in the cold frame now.
- Harden off plants started indoors or in the cold frame before moving them into the garden later.
- If the weather remains chilly in your region, sow tender summer vegetables and herbs indoors or in a greenhouse or heated cold frame at the end of this month.
- Start the seeds of summer vegetables that require 8 weeks or more indoors. Warm-weather summer crops include basil, cucumber, eggplant, peppers, squash, and tomatoes.
- Thin seedlings that have grown to size, pot them up, and place them in the cold frame or plant them out later this month.
- Ventilate the greenhouse and cold frame when the outside temperature rises above 40ºF (4ºC). Close again before sundown. Ventilation should be increased on warm days as much as possible to prevent the buildup of diseases in the damp atmosphere.
- Check plants for signs of pests and disease, which often begin to multiply rapidly as the temperatures rise. Water seedlings and plants as needed.
- Make sure plants started indoors receive plenty of light.
Vegetable Planting Outdoors in Cool and Cold Regions
- Few seeds will germinate if the soil temperature is colder than 45ºF (7ºC). Delay planting outdoors if the soil is still cold.
- Start crops in the garden under the protection of a plastic tunnel if the soil is still chilly.
- Plant out spring vegetables when heavy frost is over. Early in the month, plant onions, scallions, radishes, peas, early turnips, lettuce, spinach, and Swiss chard. Sow early peas in a sheltered spot.
- Protect cabbage, lettuce and other vulnerable vegetables in the garden with cloches, hot caps, plastic tunnels, or inverted flower pots if the nights are expected to get cold.
- By mid-month set out seedlings of cabbage, broccoli, and Brussels sprouts if the soil is not excessively wet.
- Choose a sheltered spot with moist soil, to make the first sowing of carrots, beets, and parsley.
- Seeds of beets, carrots, and parsley should be soaked for two hours in warm water before planting.
- Sow seed or set out starts of kohlrabi, leeks, onion sets, parsnips, radishes, scallions, shallots, and turnips.
- Plant lettuce, spinach, chard bok choy, kale, and broad beans when the danger of frost has passed.
- Sow early peas in a sheltered spot.
- Plant potatoes as soon as the ground is workable. Cut the tubers into 3 or 4 pieces, each with several good “eyes”, and set them in trenches, about 3 inches deep and 2 to 3 feet apart.
- Get asparagus crowns in the ground now. Remember these roots need to be planted in an area set aside for their growth over several seasons. Top asparagus crowns with well-rotted compost.
- Feed perennial vegetables with aged compost and compost tea after they begin to grow. Keep the garden free of weeds. Apply summer mulch when the weather warms.
- Water in dry regions regularly and deeply. Avoid wetting the plant foliage. Protect recently planted vegetables and herbs from drying winds.
- Before slugs, snails, and pill bugs invade your leafy greens, head them off with beer traps. Where cutworms are a problem place cardboard collars around seedlings.
- Harvest cool-weather crops as soon as they are ready. Begin to harvest spears from two- and three-year-old asparagus plants this month.
- Start sowing vegetables without protection if your weather has warmed. If you are in doubt, check your soil with a soil thermometer to make sure the soil temperature has warmed to greater than 45ºF (7ºC).
Herb Garden in Cool and Cold Regions
- Herbs can be sown in the garden when frost has passed. Sow seeds of chervil, dill, fennel, parsley, pot marjoram, and sorrel.
- Perennial and biennial herbs can be lifted, divided, and replanted now. Look for any overgrown clumps of bergamot, chives, and fennel.
Container Gardens in Cool and Cold Regions
- If you garden in containers, prepare them now. Clean pots thoroughly. Move large containers outdoors and fill them with potting mix mixed with compost.
- Cold-tolerant vegetables can be planted into containers this month.
- Water container plants as needed and fertilize them with a water-soluble fertilizer such as compost tea or worm castings.
Fruit Trees and Vines in Cool and Cold Regions
- Spray fruit trees for over-wintering pests with dormant spray oil when the temperature rises above 45ºF (7ºC) and before buds break. Spray peaches, nectarines, apples, pears, plums, and almonds with a copper-based fungicide. As long as the buds have not broken, apply a second spray to trees in about 14 days.
- Spray peaches and nectarines with a fungicide recommended for peach leaf curl. Sprinkle sulphate of potash around the root-feeding area of apples, pears, and plums to encourage good fruiting later in the year.
- Mulch established fruit trees and bushes with garden compost or rotted manure.
- Sprinkle sulphate of potash around the root-feeding area of apples, pears, and plums to encourage good fruiting later in the year.
- Prune autumn-fruiting raspberries. Cut the canes that fruited last autumn back to ground level. Prune back canes of raspberries planted last year to about 12 inches.
- Prune back the stems of newly planted and two-year-old gooseberries by about one-half.
- Plant currant bushes and raspberry canes, and water in thoroughly.
- Spray gooseberries and black currants for gooseberry mildew.
- Protect strawberry plants with cloches.
- Fertilize strawberries, brambles, and grapevines with compost when the first blossoms show.
- Train blackberries and loganberries onto support wires.