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April Cool-Region Kitchen Garden Almanac

Seedling Peas
Pea seedlings

When the crocus and narcissus bloom, the soil is growing warm enough to begin working in the kitchen garden. And if you want a sure sign that winter in your area is past, look for the first leafing out of the birch trees and the bloom of the lilacs.

Don’t rush spring if you are in a region that is just seeing the last of the snow melt. It’s too early to be in the kitchen garden if the soil is partly frozen, muddy or wet. But changes will come quickly this month; April is the month of greatest change in the garden. Spring blossoms will arrive in the north and so will many song birds.

In the United States, the danger of frost is likely to continue this month in all or part of the states in the Northeast, Rocky Mountains and Plains regions, and some parts of the Pacific Northwest,. These regions include planting zones 3, 4, 5, and 6.

Here is a kitchen garden guide for cold and cool regions for the month of April:

Soil preparation. Prepare the soil for planting: cover your beds with black plastic for several sunny days, and then dig if the soil is not wet. You can also place cloches in position to warm up the soil. When the ground is workable, dig up root crops left in garden from last fall.

Turn compost pile when it thaws. Begin a new compost pile during the spring if you don’t already have one. Use leftover leaves, grass, and non-fatty kitchen scraps.

Fork over the kitchen garden, dig in cover crops, remove weeds, rake soil to a fine tilth and spread compost if the soil is dry enough to cultivate. Prepare celery and potato trenches by adding a layer of well-rotted manure or garden compost to the trench area.

Remove winter mulch from around fruit trees, vines, and perennial vegetables that are when they flower or begin to sprout new growth.

Greenhouse and coldframe in colder regions. If the weather remains chilly in your region, sow tender summer vegetables and herbs in the greenhouse or coldframe by the end of this month. Hardy and half-hardy vegetable starts should be ready for the coldframe now in less cold regions, having been sown last month. Start the seeds of summer vegetables that require 8 weeks or more indoors before transplanting out. Warm-weather summer crops include basil, eggplant, peppers, squash, and tomatoes.

Thin seedlings that have grown to size, pot them up, and place them in the coldframe or plant them out later this month.

Ventilate the greenhouse and coldframe 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.

Container gardens. If you garden in containers, prepare them now. Clean pots thoroughly. Treat wooden boxes, troughs, and tubs with preservative. 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.

Sow vegetables outdoors. When the danger of heavy frost is past begin sowing cool-weather crops. You can first warm up the soil by covering it with polyethylene or cloches. Cover vegetables already in the garden with horticultural fleece or floating cloches if you expect a frost.

Start sowing vegetables without protection if you live in a mild area or 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). Few seeds will germinate if the soil temperature is colder. Delay planting outdoors if the soil is too cold.

Set out quick growing cool-weather transplants and sow leaf and flower vegetable seeds as soon as the danger of heavy frost is past. Cool-weather leaf and flower crops include: bok choy, broad beans, broccoli, Brussels sprouts, cabbage, cauliflower, chard, kale, lettuce, peas, and spinach. Cool-season root crops can also be planted out in the garden if the soil is not excessively wet. These include beets, carrots, kohlrabi, leeks, onion sets, parsnips, early potatoes, radishes, scallions, shallots, and turnips.

Plant peas, lettuce, spinach, and chard when the danger of frost has passed. Sow early peas in a sheltered spot. A week later, plant cabbage, broccoli, Brussels sprouts, celery, and endive. 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. Seeds of beets, carrots, and parsley should be soaked for two hours in warm water before planting. Protect cabbage, lettuce and other vulnerable vegetables with cloches, hot caps, plastic tunnels, or inverted flower pots if the nights are expected to get cold.

At the end of the month if the danger of frosts is past, plant corn, beans, melon, cucumber, squash, parsley, pepper, tomato, and eggplant. Don’t set out tomato plants or warm season crops too soon.

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.

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.

When day time temperatures average 65ºF (18ºC) or greater, warm-weather crops can be sown or transplanted out. Warm-weather crops include: basil, beans, corn, cucumbers, eggplant, peppers, melons, squash, and tomatoes.

Feed perennial vegetables with well-rotted 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.

Harvest cool-weather crops as soon as they are ready. Begin to harvest spears from two- and three-year-old asparagus plants this month.

Before slugs, snails, and pill bugs invade your leafy greens, head them off with beer traps.

Fruit trees and vines. 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.

Plant new fruit trees, avocadoes and citrus fruit when the soil is workable. Mulch established fruit trees and bushes with garden compost or well-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 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 logan berries onto support wires.

Written by Stephen Albert

Stephen Albert is a horticulturist, master gardener, and certified nurseryman who has taught at the University of California for more than 25 years. He holds graduate degrees from the University of California and the University of Iowa. His books include Vegetable Garden Grower’s Guide, Vegetable Garden Almanac & Planner, Tomato Grower’s Answer Book, and Kitchen Garden Grower’s Guide. His Vegetable Garden Grower’s Masterclass is available online. Harvesttotable.com has more than 10 million visitors each year.

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