March Growing Tips

By Raintree Horticulturist Theresa Knutsen

PLANTING

Planting and growing raspberries:

Raspberries are typically grown in a two foot wide row. Prepare the soil for planting by first clearing weeds in a 3-4’ wide strip the length you are planning to plant. Put a 3-4” thick layer of composted manure (cow, steer, or other ruminants, not chicken) or leaf mold on the surface of the row. Work it in to the top foot or so of soil, then rake up to form a mound about 2’ wide at the base. Then make a furrow 3-4” deep down the center of your mound. To determine your row length allow 18-24" per plant, which will generally fill the bed in in 2-3 years.
 
You will receive bare root plants that look like a stick with some roots at the bottom. Plant your raspberry every 18-24 inches along the row, starting 1 foot in from the end, laying the roots along the furrow (don’t worry if they overlap with the next plant). Cover the roots with 2-3” of soil and water in.
 
Raspberries spread vigorously from their roots. Keep your plants in check by roto-tilling or digging around the mound to remove spreading roots, 2-3 times a year after the first year. Install support for the vigorous canes during the first year. Keep the soil in the mound moist, but not constantly wet. Apply composted manure to the mound each winter.

July (floricane) bearing and fall (primocane or ever-) bearing raspberries have different pruning requirements, see the Raintree Nursery Plant Owners Guide for instructions. To support ever-bearing raspberries 1-2 wires down the center of the bed, at 3-5’ high, will suffice. To support July bearing types attach 2 cross-bars to each end post; make one 18” long and install at 3’ high, the second crossbar 24” long at 5’ high; string wire to the crossbar ends to make a v-shaped area for the raspberries to grow within.

Planting in Cold Climates
Planting time continues for those of us living West of the Cascade Mountains in the Pacific Northwest, and other similar climate locations throughout the country. So long as the ground is not under water or water-logged, frozen, or covered with snow, and the weather is above freezing when you plant, you can plant dormant potted or bare root plants.
 
For optimal results, day time temperatures should be below the mid-60’s for several weeks following planting (to give roots time to establish before top growth becomes too demanding). Follow the basic planting instructions in the Raintree Owners Manual we send with each other. If you did not receive one, or have misplaced it, you can also view it on our website.
 
Planting in Warm Climates
Those of you living in the southern U.S. may be regularly experiencing day time temperatures in the 70’s. If this is the only time you can acquire particular plants, follow the late planting instructions in the Raintree Nursery Owners Manual or the following to ensure success with your new plants, or pre-order plants to be shipped to you at your optimal planting time early next spring.
 
If you choose to plant out in a permanent location right away, mulch the soil surface well after planting, irrigate deeply and often enough to keep the soil evenly moist, not soppy wet, and provide shade until the plants are well-established. Warmer air temperatures encourage faster shoot growth than root growth, creating water stress in the tree, shade helps to reduce the water needs of the plant and give the root system time to catch up with the top of the plant. Follow the same techniques when planting out our dormant potted plants. Providing shade when planting will help these plants adjust to the change in environment.
 
Plant your new plants in a temporary, shady location, mulch, and water regularly through the summer. In the fall, when the worst of the summer heat has passed, move the plants to their permanent location. By the following spring they will be well-established and ready to perform.
 
Plant your new plants in containers, if receiving potted put in somewhat larger containers, maintain them in a protected location, and plant in their permanent location in the fall when the worst of the summer heat has passed.

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Non-Dormant Hardy Plants
Sometimes you might receive non-dormant plants that would normally be dormant and ready to plant outside. Our hardy plant greenhouses are kept to a minimum of about 28-30°F at night, but by February the day time sun can warm them up well into the 70’s. The resultant new growth is tender and can be damaged by freezing weather, especially below 28°F for more than a couple of hours. Most plants will put on a second flush of new growth after early frost damage, in about 4-6 weeks. To prevent frost damage on non-dormant potted plants you have received here are a couple of options:
 
Keep the plants where they will receive bright light and remain cool, but above freezing, until danger of frost is past. If you can keep the plants cool (32-50°F) their growth will be slowed down, so they won’t stretch as much, and the leaves will be a little tougher. Fertilize them lightly with a low to medium nitrogen fertilizer, such as fish fertilizer with kelp to supply micro nutrients, or maybe compost tea. The kelp fertilizer may improve plant tolerance to cold temperatures.
 
As the day time temperature you are holding your plants at increases so will the rate of growth of your plants. Provide supplemental light if the plants seem to be stretching or getting leggy, fertilize lightly as above.
 
If you are expecting night time temperatures to be mostly above freezing, with an occasional frost still possible, then you could go ahead and plant outside. Be prepared to put some frost protection over your new plants if necessary. A paper bag, spun-bonded floating row cover (such as Reemay), or a blanket (with support) will provide a couple degrees of protection.
 
Plants that have been actively growing indoors need to gradually get used to being outside in the direct sun and wind to continue to perform their best. Put them outside in a partially sunny location for a few hours a couple of days, then over the rest of the week gradually increase the time and decrease the shade until they spend the full day outside. After a week you can plant following instructions in the Raintree Nursery Owners Manual.

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INSECT/DISEASE CONTROL:

Winter control of aphid, scale or mites

Did you notice many aphids, scale insects, mites, or other soft-bodied insects in your fruit trees or bushes last summer? If so, applying a dormant oil spray in winter, or when plants are still fully dormant, smothers over-wintering insects hiding in the bark. If you didn’t spray when your trees were fully dormant you can still apply a delayed dormant oil or ultra-light oil spray to smother those insects before their populations have a chance to rebuild. These types of oil spray use a lighter weight oil than dormant oil, which is less likely to cause stem or foliage burn. Avoid spraying when bees are active in the trees, and follow label instructions.

Control scab, powdery mildew, brown rot, or corynium blight in apple and pear

You may have noticed scab or powdery mildew in your apples or pears last year, or brown rot or corynium blight in your stone fruits. Applying fungicide sprays can help keep those diseases under control this year. See the Raintree Plant Owners Manual, page 12, for timing of sprays. Your local co-operative extension service should have publications indicating best timing and strategies for disease control in your area. It is possible to control scab with just a few sprays in the spring, by monitoring rainfall patterns and temperature. For more details you can read about this approach in “The Apple Grower” by Michael Phillips, (#S005), or ask about a bulletin at your co-operative extension office or web site. To find your local co-operative extension click on Growing Info in the top tool bar, then select useful links under plant care.

Control Mummy berry in blueberries

Mummy berry disease is a fungal disease that infects blueberries, causing flowers to turn brown and wither, black discoloration and wilting in newly emerging leaves and shoots, and immature berries to be filled with white spongy fungal growth. Ultimately the infected fruit turns reddish to tan in color, then they become gray, shriveled and hard. I’m not sure whether there are chemicals the back yard grower can use to control this disease.  There are cultural techniques you can use, however, to help keep the mummy berry fungal organism to a minimum. Sanitation is your most effective tool. Clean up and destroy as much infected material as you can from the bushes and the ground in the fall. In the spring (late February to early March in the Pacific Northwest) any remaining infected material will start producing spores. When the blueberry buds start swelling in the spring, mulch with 1-2” of sawdust to cover infected material under and near the bushes to prevent spores from splashing up. Shallow cultivation, about 1” deep, can also interrupt the spore forming process and will need to be repeated several times over a period of about 3-4 weeks. There are two infection phases, one at bud swell, the second about 3 weeks after the first flush of flowers have withered. Your local co-operative extension service will have information on timing in your location, as well as other control possibilities and more information about the life cycle of this disease. The useful links section found n Growing Info (top tool bar) has a link to help you find your local co-operative extension service.

 
CULTURAL PRACTICES:
 
Fertilizing
Apply a ½ strength dose of fertilizer to acid loving plants, such as blueberries, lingonberries and cranberries as buds start to swell on the plants. Use a fertilizer that is specifically formulated for blueberries or rhododendron, such as Organic Blueberry (#T143) fertilizer. Follow with a light mulch of wood chips or pine needles under the blueberries. Apply a second ½ dose of fertilizer when the flowers fall. Raspberries, asparagus, and rhubarb appreciate a mulch of well composted cow or steer manure applied before new growth emerges in the spring. A one inch layer of compost spread under the edge of the leaf canopy of most fruiting plants will help maintain fertility. If your plants seemed less vigorous last year than they should be, a little fish fertilizer with kelp (seaweed) may be helpful.
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Control Weeds
Keep weeds controlled around trees and shrubs, especially those that were planted more recently. Be careful when working around blueberries, their shallow roots are easily damaged by vigorous digging and weed removal. If your blueberries have a lot of weeds under them you might try cutting the weeds to the ground, putting down a ½-1” layer of peat moss, several layers of newspaper or a layer of cardboard, and then wood chips on top. Most weeds will be smothered. More persistent perennials that eventually come back through the mulch, can be repeatedly cut off (every 10-14 days) until their roots starve out.
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New plantings of ground covers, such as cranberry, lingonberry, all-field berries and strawberries need regular weeding. Even after they have filled the space, some weeds may still come through. Putting down cardboard or layers of newspaper covered with mulch between the new plants will help reduce weeds as well as contribute to building the soil organic matter.
 
Permanent weed barrier fabrics may seem like a good solution for controlling weeds, but only if used for just a year or two, or only just near the trunk of the tree. Longer use interferes with organic matter breaking down on the surface and rebuilding humus in the soil, which contributes to the health of the soil and your trees. Temporary weed barrier fabrics, such as #T140 (4'x4' sheet) or #T445 (4' x50') will provide the weed control necessary to establish plants, and then decay after about 2 years, so you don't have to remove them. The 4'x4' sheet is an ideal size for tree and shrub planting. Strawberries planted through holes in the barrier will thrive in the lack of competition, and berries are kept off of the soil.
 
Factors to consider if you have had pollination problems
If you have had problems with adequate pollination in the past, the following are some factors to consider.  Look at your fruiting plants as they come into bloom, especially those that did not set fruit well last year. Are there lots of flowers? Increasing summer shade or excessive fruit production the previous year can reduce the number of flower buds the plant produces. Notice if there are plenty of bees in the flowers. If you have bees and flowers, are the varieties that should be providing pollen for each other blooming at the same time? What is the weather doing? Is there a lot of cool wet weather that will support brown rot disease in the blossoms, effectively interfering with pollination, or keep bees from flying? Frost can cause physical damage that interferes with pollination, or provide a site for a secondary infection that damages the flower. Sometimes misting overnight or smudge pots are used to protect blossoms from frost damage. Another possible technique is to run a string of outdoor Christmas lights in the tree, turning them on when frost threatens.
 
Do you see ants or earwigs in the flowers? Both insects can cause significant damage and interfere with fruit set. If you are growing kiwi, look at the blossoms and compare them to the pictures in our catalog. Make sure you have both male and female flowers. Uncover protected plants in flower during the day to allow access for pollinating insects.
 
Daffodil and Tulip Care
Remove daffodil and tulip foliage six weeks after flowering, or when the foliage has yellowed. Don’t braid, rubber band, or otherwise mutilate the green leaves- they are feeding the bulb for next years bloom.
 
Mason Bees
As temperatures warm in the spring the mason bees start emerging from their over-wintering cocoons. The males emerge first, followed by the females after a few days. Make sure, if you haven’t already done so, that there are plenty of clean new tubes for the females to deposit their eggs in. Newly emerged bees can be hungry, review your landscape and make sure there are flowers with nectar and pollen for them to feed on, especially if your fruiting trees haven’t opened their blossoms yet. Pussy willows, filbert catkins, Pieris japonica, Indian Plum (a northwest native) and Mahonia species (Oregon Grape) are all good early season bee forage plants, and are attractive in the landscape as well. If you are managing the release of your mason bees (Feb Growing Tips) watch your early apples and European plums (I’m assuming asian plums have already come into bloom). When you see the beginning of color in the buds it is time to put another batch of cocoons out, or continue with putting a batch out every 6 weeks through May.
 
Container Plants Care
As the time approaches for putting frost tender house-bound plants back outside, keep an eye on the weather, be patient, and wait until all danger of frost is past. Harden off plants for a smooth transition to outside living. Put them outside in a shaded location for a couple of hours the first day, and over the next two weeks, gradually increase the amount of sun exposure and length of time they are outside. Continue fertilizing at the late winter/early spring rate of ½ strength while plants are inside or in transition. When they are outside and actively growing, fertilize at full strength. Remember to monitor for presence of unwelcome insects. Early treatment will prevent heavy infestations later.
 
Select a fertilizer that is appropriate for the plant you are growing to get optimal performance in the container. Use citrus fertilizer for citrus plants, and blueberry/rhododendron fertilizer for vacciniums (blueberry, huckleberry, lingonberry and cranberry). For Bananas, encourage lots of vigorous growth initially with a foliage supportive formula that has a high nitrogen content, then switch to a formula that is higher in phosphorous (a bloom fertilizer) to encourage flower and fruit development. Bamboo, lemon grass, and sugar leaf all benefit from higher nitrogen fertilizers once they are actively growing. Many fertilizers either list what kinds of plants they are formulated for, or what kind of growth they support (such as foliage vs. fruiting).
 
Start fertilizing your outdoor container plants as their buds begin to swell. If you are using a liquid fertilizer, at first use ½ strength doses, once a week or so. As your outdoor temperatures increase and roots are better able to absorb nutrients, you can increase to a standard dose.
 
Slow release fertilizers: If you prefer not to mix liquid fertilizer in when you are watering, consider spreading a long lasting slow release granular or pelleted fertilizer on the soil surface (or you could have mixed some in when you re-potted last winter).  Most slow release fertilizers depend on temperature to regulate nutrient release. Don’t expect much performance from the fertilizer until the weather has warmed up. Choose a long release period (such as 6-9 month) to ensure your plants continue to grow well through the summer. Use an appropriate formulation for what you are growing. Fruiting plants need a different balance of nutrients than foliage plants.
 
Pruning
Continue dormant season pruning. The best time to prune stone fruits is as the buds swell. This is because the wounds seal more quickly, reducing opportunity for fungal infections to occur. If you are growing tip-bearing apples such as Thompkins King and want to encourage them to branch, wait until new growth has extended 4-6 inches, then make heading cuts into last year’s wood to encourage branching where needed. Thinning cuts can be made any time during the dormant season.
 
As spring progresses, even though many of your plants have started to grow, pruning may continue. It’s not true that you have to stop pruning when plants have come out of dormancy. Early blooming shrubs, such as forsythia, winter jasmine and flowering quince, are best pruned immediately after they are done blooming, because they set flower buds for next springs bloom on this year’s new growth.
 
Still not sure how best to prune that plant? You may be able to find a local resource to teach you. Explore your local co-operative extension office, local garden clubs, local chapters of NAFEX (North American Fruit Explorers), CRFG (California Rare Fruit Growers Association), Western Cascade Tree Fruit Society, or the WWFRF (Western Washington Fruit Research Foundation). Please see the Useful Links section under Growing Info to find these organizations.
 
There are also some useful books, DVD’s and pamphlets. At Raintree Nursery some of our favorites include: Easy Steps to Tree Fruit Pruning (#S520D), DVD, by Gary Moulton; Pruning and Training your Home Orchard by Pacific Northwest extension; and The Pruning Book by Lee Reich.  There are many  more in our book section for you to explore. To discover almost any pruning technique that has been developed I also enjoy Pruning and Training revised (#S325), by Brickel and Joyce.
 
Irrigation
Now is a good time to look over stored irrigation equipment and order replacement parts. Make sure you have a plan for irrigating new plantings this year and order additional parts if needed. All new plantings need at least some irrigation in their first summer, unless you receive about 1” of rainfall every week. In warmer drier locations it may be time to install (re-install) systems and start irrigating. We get a lot of our drip irrigation equipment from Dripworks. Call them at 800 522 3747 and they will help you pick out what you need.
 
In warmer drier locations, or when the soil drains quickly, regular irrigation of new plants is essential for establishment, and may also be necessary for mature plants to thrive. Provide enough water to penetrate the soil to 1 foot deep, then wait to irrigate until the soil has begun to dry out about 6” below the surface. Check the moisture content of the soil by poking your finger in to a depth of about 4-6”. It is hard to sense wet or dry with your finger, but it is easy to sense temperature. If it feels cooler than the air temperature there is generally plenty of water available, if the soil feels closer to air temperature then it is time to water again. Mulching the soil surface with bulky material, such as wood chips or straw, reduces moisture loss from the soil surface.
 
Fruit Processing
Do you still have fresh apples in storage? Red Belle de Boskoop, Karmijn de Sonneville, Enterprise, King Edward VII, Gold Star and Melrose all have a long storage life. Comice, Bosc, Highland and Conference European pears, and Korean Giant and Chojuro Asian pears also store well, though not quite as long as the apples. Sort out and toss spoiled fruit.
 
Medlar and Kiwi have a long storage life when picked at the firm ripe stage (seeds mature but fruit still firm) and kept cool. Bring them into a warm place for several days to finish the ripening process.
 
Start picking strawberries in the greenhouse in the next month or so from established plants, everbearing varieties such as Tristar or Eversweet, and the alpine strawberries (Mignonette or Yellow alpine for example) will produce fruit spring through fall.
 
Frequently Asked Questions
What do I do if my plants have come but I can’t plant right away? The goal is to keep the bare root plants cool and dormant, and protect the roots from freezing or drying out. You can generally hold the plants up to two weeks in the bags they arrived in, in a cool (35-45°F) location. Check the bags for moisture a couple times, the shredded paper around the roots should be moist and there should be humidity present on the inside of the bag, standing water more than a ½” or so is undesirable. Alternatively, you can heel the dormant plants in a loose pile of soil or compost outdoors (in the shade if temperatures are on the warmer side) until you are ready to plant.
 
Potted dormant plants (evergreen or deciduous) can also be held in a cool location, or buried outdoors in the compost pile to the rim of the pot. Potted hardy plants that are showing new growth are no longer dormant, and that new tender growth will probably be damaged by temperatures below 30-32°F. Keep them in a cool (35-60°F) but bright location to slow new growth until most danger of frost is past, harden them off, and plant. If late frost threatens, you can provide temporary cover to protect them. If the new growth is damaged by cold temperatures another flush of growth generally occurs within a few weeks.
 
Hold frost tender plants at a moderate temperature, 50-65°F, with bright light, until all danger of frost has passed before taking them outside for the summer.

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