By Raintree Horticulturist Theresa Knutsen
Featured this month is information on:
In the Pacific Northwest plants become fully dormant in December. Dormant season pruning generally begins in January, after the distractions of the winter holidays. If there is still a significant risk of snow, ice or wind damage in your trees it may be best to wait another month or so to start pruning.
Certain plants are best pruned while fully dormant, to prevent ‘bleeding’, or excess sap production, from the wounds. Kiwi, grape, and fig are good examples of ‘bleeders’. Maples also bleed, thus maple syrup from sugar maples. If you want to collect sap to make syrup, make diagonal cuts in the trunk through the bark when there is a pattern of nighttime temperatures below freezing, and day time temperatures into the 40’s. If you just want to shape your maple trees then choose a time with more stable temperatures, but still cool in the 30’s.
You can also start pruning apple, European pear, quince, elderberries, mulberries, and medlar. Other types of plants are best pruned later in the season, for various reasons. To reduce fungal disease infection opportunities, wait to prune stone fruits until their buds are starting to swell (plum, cherry, peach, almond, and apricot). Tip-bearing apples, such as Thompkins King, are pruned after the new growth is out 4-6”, if you are making heading cuts to encourage branching. And, of course, it’s best if you have a dry day when you prune. You’ll be more comfortable, and you’ll be less likely to spread disease.
Delay Asian pear pruning until the weather has warmed up and dried out fairly well to control pseudomonas infection, usually April-June, depending on your location. See the Raintree Plant Owners Manual, pg 17, that came with a previous order; or download a copy from our website, found in Growers Info (see our home page, side bar). Since you won’t be pruning your Asian pear for a few months it is helpful to tie colored yarn or flagging where you want to make your cuts while the tree is dormant. This will help you remember what you want to remove later on when there is foliage on the trees.
January through February is the best time to cut back summer-pruned laterals on red or white currant and gooseberry cordons and to shorten leaders on red or white currant and gooseberry bushes. Thin out 1/4 to 1/3 of the oldest canes in your blueberries. See the Raintree Plant Owners Manual, pgs 10-14.
Thin out some of the oldest and largest canes on multi-stemmed shrubs such as mock orange and forsythia, and prune out winter damage. Bring branches of flowering quince, Japanese plums and forsythia indoors to force into bloom. Soaking the entire branch in tepid water for a few hours accelerates the opening of the flower buds.
My favorite pruning references for fruit producing plants are:
Easy Steps to Fruit Tee Pruning (#S520D), by Gary Moulton, this DVD is excellent for those who need to see it done.
Training and Pruning Your Home Orchard by Pacific Northwest Extension (#S335). The diagrams and instructions provide much of the same information as the DVD above, in a pamphlet you can take out to the orchard with you.
The Pruning Book (#S327), by Lee Reich, he covers fruiting trees and shrubs, ornamentals, and vining plants, including a useful section on espalier pruning.
Pruning and Training-Revised, by Brickell and Joyce (#S325). Clear simple text and many line drawings guide the novice pruner through basic fruit tree, shrub, berry and ornamental plants pruning. Espalier and other advanced techniques are covered as well.
The Grape Grower, by Lon Rombaugh (#S185), provides a good explanation of the two main systems of pruning, and a variety of training methods using those two systems. He also has some interesting tips on increasing the size of both individual grapes and the bunches.
Growing Kiwifruit from Oregon State University (#S240). Kiwi are not trained and pruned like a grape, although there are some similarities. The diagrams in this 20 page booklet will show you how to manage them properly for maximum production.
We also include our Raintree Plant Owners Manual (found in Growers Info) with every plant order which includes basic pruning tips to get you started with the fruiting plants we offer.
Along with understanding temperature patterns in your area (November Growing Tips), it is also important to determine how much, and for how long daily, your plant will receive sun in a particular location. Fruiting trees, such as apple, pear, and plum, initiate new flower buds for the next spring season between late June and early August, depending on your location. Typically, a minimum of eight hours of direct sun daily are needed during the blossom initiation period, for maximum flower bud potential. Blueberries are fine with a minimum of six hours. Your plants may still thrive and grow with fewer hours of direct sun during the blossom initiation period, but the next year’s fruit production will probably be reduced.
How much root and branch room is in that spot I want to put a plant in? Find out how tall and wide the plant you are interested in is expected to grow to, and make sure it will fit where you intend to put it. We put expected managed height and width (not maximum) for most of the plants In the Raintree Nursery catalog, look for the outlined box with Useful Facts or the main plant description; on-line select Growing Info in the side bar on our home page and then Plant Info. If you do not currently have a catalog you may down load a copy from our web site. With pruning you should be able to hold a tree comfortably to 75% of its potential, any smaller and you will be in constant battle with it. There are pruning techniques that do allow you to keep a tree significantly smaller, if you are diligent and attend to them regularly. See #S325 Pruning and Training-Revised by Brickell and Joyce for instructions. If you have a space that is long and narrow, there are some options for you, such as a hedge of blueberries or blackberries, or you could train a fruit tree as an espalier.
Why soils are important. It is also valuable to know what your soil is like, such as heavy clay, sandy, high or low level of organic matter, pH, soil depth, and nutrient levels. Have your soil tested professionally (ask your local co-operative extension office for recommendations in your area), or explore it yourself. Wet soil that is high in clay tends to be sticky, silt soils tend to feel smooth, and sandy soils tend to feel gritty. Organic matter tends to darken the color of the soil, bind a sandy soil, or lighten a clay soil. A simple test kit (#T496 Rapitest Soil Tester) will help you determine the pH and primary nutrient levels in your soil (nitrogen [N], phosphorous [P], and potassium [K]). Different plants evolved, or have been selected to perform best, in specific soil conditions. A cactus planted in heavy wet clay would start suffocating from lack of oxygen to the roots immediately; an acid loving blueberry planted in typical garden soil pH of 6.5-6.8 would be unable to absorb nutrients, leading to unhealthy yellow or red foliage color, lack of vigor, and eventual death. An apple tree planted in a soil with pH below 6, that tends to hold a lot of water in winter and spring, and does not have much depth above a hard-packed subsoil will tend to just sit there, or die, because the root system is in such a hostile location. A blueberry planted in the same location may thrive.
In our catalog, again in the outlined box, you can find out what the preferred growing conditions are for most of the fruiting plants we offer; on-line select Growing Info in the side bar on our home page and then Plant Care. For most soils, the best modification for the soil structure is to add organic matter. Clay soils benefit from straw or leaves piled on the surface and allowed to decompose. Sandy soils benefit from any balanced compost or organic material applied to the surface and mixed in over the entire planting area, or better yet, expected root zone area, before digging the planting hole. Nutrient and pH issues are corrected with amendments (lime or sulfur to correct pH, and fertilizers). Avoid affecting only the planting hole, tree roots in particular are eager to spread out and establish. Adding amendments to a broader area encourages actively spreading root growth, and therefore stronger top growth.
If your soil has been recently disturbed, is low in organic matter, or is imported, your fruit trees will also benefit from the addition of mychorrizal fungi at planting time, #T185 Myco Paks. The fungal organisms in these packets are normally found in association with the root systems of healthy deciduous trees and some berries, particularly those types of plants that would normally be found in a temperate zone deciduous forest. They support and augment root function, improving water and nutrient up take, particularly phosphorous, and help protect against some disease organisms. They are present in most healthy soils that have had native deciduous trees or blackberries growing on them. Soils that have been disturbed, are low in organic matter, or have been regularly fertilized with chemical fertilizers will tend to have little or no beneficial mycorrhizal organisms present. Plants that have been removed from the soil and the soil washed off the roots, or grown in a container by a commercial grower with chemical fertilizers will usually not have beneficial organisms on their roots. Inoculating the roots of your trees or berries at planting time will help ensure that your fruit tree and strawberry plants will establish and grow well in their first year. After planting apply a mulch of organic matter that was brown when harvested, such as fall leaves or straw, for optimal support of the fungal organisms. You are duplicating what would normally happen in a hardwood forest, where most of our fruit trees originated.
Select 'Choosing Which Plants Will Work For You' under Growing Info (side bar on our home page) if you still have questions, or want to see the rest of the discussion on selecting plants.
Winter storms and arctic cold events can be damaging to trees and shrubs. Remember to inspect your plants for broken limbs or lodging over in soppy wet soils after storms. Make clean cuts when you find broken, torn, or split limbs. Clean cuts will be less susceptible to fungal infection than ragged breaks.
If you have lost the top of a more recently planted tree you may be able to train a new top for it. If the break occurred above the graft, and above a flexible side shoot, you can train that shoot to be the new leader with a splint. Make a clean diagonal cut ¼” above the side shoot, tie a piece of bamboo or other stiff material to the trunk in two places below the shoot, then carefully bend the shoot upwards and tie it to the bamboo in two places, to create a new top on the tree. If there is no flexible side shoot available, but the break is above the graft, make a clean diagonal cut ¼” above a bud or node, and cut back any non-flexible side shoots within 6” of your cut to one or two buds. In the spring after the new growth is out about 6”, select the strongest most vertical shoot, remove the others, and splint as necessary to keep the shoot straight.
Sometimes newer trees break off at the graft or below, in that case there is not much you can do. All you have remaining is the rootstock, which you can either allow to grow a new top to graft onto, or remove and replace with a new tree.
If your tree has developed a strong lean, or has fallen over, you may be able to help it re-establish its upright habit again. If the roots did not come out of the ground, place a prop against the trunk or under a sturdy limb and push the trunk straighter. A big lean may need to be pushed back up in smaller increments, to avoid causing any further root damage. Sometimes snow weight puts a bend in the tree. If the trunk is not too thick you may be able to push it back up straight. The tree will need help to stay upright, secure a sturdy metal rod or 2x piece of wood to it. Tie the splint to the tree in two to three places below the bend, and within and above the bend so the splint holds well. Keep the splint on for at least one growing season.
If the tree has leaned almost to the ground, or completely fallen over, most likely the roots on the opposite side have either broken off or pulled out of the ground. Before trying to straighten the tree dig under the roots on the opposite side to make a hole the roots can settle back into when you push the tree back up. Cover the roots with soil after you have righted the tree. To balance the top of the tree with the root damage it is best to prune the top of the tree also, up to 50% of the top of the tree if there was a lot of root damage. Make more thinning cuts than heading cuts, leaving as many terminal buds as you can which will send the message to start growing to the roots in the spring. Stake the tree, using 2-3 stakes, protect the trunk with rubber strips (or something similar). Leave the tree loose enough to be able to move an inch or so in any direction, but not much more. Remove the stakes after one season if the roots were not broken, after 2-3 seasons if there was a lot of root breakage (to give the root system time to fully re-establish).
Do your grapes need fertilizer? The book “The Grape Grower” #S185 describes how to manage your soil for the best balance between fruiting and growth of your grape vines (chap. 4). Or you could take a more simplified approach for back yard grapes. First year vines often don’t need fertilizer. If the leaves were deep green and the vine made good growth then there is no need to fertilize. The best fertilizer to use, if your vines did not put on much new growth, or the leaf color was more yellow, is compost. Excess nitrogen in the soil stimulates excessive vegetative growth, at the expense of fruiting. It can also have a negative impact on the quality of your finished wine. Annually observe the vigor of the vines, to determine whether compost needs to be applied. On average apply compost starting in the third year and every year or two thereafter. Compost is best applied early spring, 2-3 weeks before leaves start to emerge from the buds.
We plan to ship mason bees mid-January through the end of February, weather permitting. When you receive your bees they need to be kept cool until you are ready to release them. Keep them in the refrigerator at 36-39° F. It is important to maintain proper humidity for the bees in a frost free refrigerator. Poke several small holes in a plastic bag, put the cardboard box of cocoons inside that bag along with a barely moist paper towel, close the bag, and put it in the refrigerator. In addition to the Mason Bees we also offer the Green Raspberry Bees. These are similiar to the Mason Bees but they fly later in the season and are the best pollinators for berries and other fruits that flower later in the season.
Mason bees will emerge naturally, in response to warming spring temperatures, if you set up the nest box and release box (with cocoons inside) as soon as you receive them. They will survive short periods of exposure to temperatures below zero, but if you expect you will have long periods of sub-freezing weather it will be best to store the bees in the refrigerator until winter has moderated. If you store your bees in the refrigerator you can time the release of your bees to coincide with the bloom time of trees, or groups of trees, in your orchard. If you are just starting a population, you will need to release all of your bees at the same time. Wait to release them until you see flower buds in your orchard beginning to swell, or about 3 weeks before the flowers open.
Place the straws filled with cocoons in the release box you purchased with your straws of bees. The Royal Bee House #T332 also has room for the straws. The bees prefer to emerge from a small dark hole into the rising sun to the east, stepping out onto a small platform they can get their bearings from before they take flight. The hole needs to be above the bottom of the release box, and the same diameter as the straws or tubes in your nest box. Locate the release box near the new nest box the bees will use, so they know where to find it.
You can maximize the pollination potential of your mason bees by releasing them just prior to the bloom of each of your major fruit bloom seasons. Store them in the refrigerator at 36-39° F as soon as you receive them, or right after you clean your established population in the fall (see October Growing Tips for more on cleaning). Keep the bees well cushioned (on a pile of toilet paper, for example) in a container that is porous, so they can breath. Then follow the directions above for keeping them in optimal condition in the refrigerator.
Put a quantity of bees in a release box as each type of fruit is preparing to bloom, or about every 6 weeks. Margriet Dogterom’s book “Pollination with Mason Bees 2nd Edition’ #S427 has instructions on making release boxes from a tin can or cardboard box if you do not have enough release boxes. Be sure to have new, clean places for your bees to deposit their eggs into when they emerge, although it will be a few days before they are ready to use them. Either insert new clean straws in the Calm Bee Nation blocks you used last year, or set out Bee Diverse Stacked Trays you cleaned last fall after removing and storing the bees.
Peaches: Apply the second spray for Peach Leaf Curl control, approximately 4 weeks after your December spray (Raintree Plant Owners Manual, pg 17)
If you are planning to do some grafting this year, December through February is the time to Collect and Store your Scion wood. Instructions are provided on the rootstock page in the Raintree Nursery catalog or here: You need the previous seasons’ healthy vegetative growth for the scion (the shoot you cut from a desired variety that is used to propagate a new tree). Water sprout wood (the vigorous vertical growing shoots you normally remove from the center of the tree when you prune), or the terminal end of major growth at the top of the tree and the south side of the tree, will be most likely to have the flat pointed vegetative buds you need, instead of the plump fruit buds you don’t need. The wood needs to be about pencil diameter, and can be cut to 8-12” long pieces for convenience. Clean the wood with a mild bleach solution (1 tsp bleach/ 1 quart of water), dry, and place it in a plastic bag. Put a barely moist (completely wrung out) paper towel in the bag to provide humidity, seal, and store in the refrigerator until you are ready to graft. Scion wood, properly cleaned and not too wet or dry, can be stored 3-6 months; scion wood from early spring blooming plants will only store about 3 months. Scion wood collected during sub-freezing day-time temperatures will have less sap in it, and may not store or perform as well as material collected when day-time temperatures are above freezing See the rootstock page in our catalog for more information on collecting and storing, and to select the rootstocks you will need to graft on.
Container Plants Care:
Because of shorter day length, most houseplants, even those which don’t lose their leaves, will not be actively growing now, even citrus with ripening fruit. So this is the time to re-pot if it’s been a couple of years since the last time. Move your plant into a slightly larger container; or trim roots ½- 2” around the sides, 1-4” across the bottom, and put back in the same container with fresh potting mix to maintain size (the larger amount to trim is for a 20” diameter container, or larger, the smaller amount is for a 6-8” diameter container).
After re-potting, your indoor plants will also benefit from pruning and shaping; delay pruning citrus branches which still have some fruit on them until after harvest. Pruning potted fruit trees or shrubs is similar to pruning plants in the ground; make heading cuts where you want more branching, thin out branches that are getting too crowded. Citrus can be maintained in an open center or central leader tree form and be sure to remove rootstock suckers. Pineapple guava and pomegranate are multi-stemmed shrubs, both benefit from thinning out older shoots to make room for new ones. Pomegranate bears fruit on new growth, and is best pruned just before new growth begins; pineapple guava bears fruit on last year’s wood.
Lemon trees may start to look a little ragged in January. So long as they are not over-watered, they will burst out with new growth next month and replace the previous year’s old tired leaves. Keep plants away from windows that can be rather chilly over night in colder climates. Provide supplemental lighting if plants are looking leggy or more yellow. Begin feeding when new growth starts to show.
Irrigation: Regularly check your potted plants that are over-wintering in a cool protected location. Make sure the soil remains moist, but not sopping wet, so roots don’t dry out.
Planting of potted and bare root stock can begin in January in moderate winter climate locations. In some southern areas January is the best month for planting. West of the Cascade Mountains in the Pacific Northwest, so long as the ground is not under water or water-logged, frozen, or covered with snow, you can go ahead and plant. Planting at this time is almost as good as planting in the fall, roots have plenty of time to dig in and establish before the tops of the plants start demanding water and nutrients in the spring. Be sure to read the Owners Manual we send with your new plants for specific planting instructions.
We ship to California and Arizona in early February but we can’t ship to the Southeast until early March because plants in transit could be damaged while crossing the frigid Rocky Mountains.
For our customers in the deep South! If you are in one of those southern sunny locations where the optimal planting time is before we are able to begin shipping to you, you may need to take special care with your plants when you do receive them. Please see our Plant Owner’s Manual, pg 2, for planting when the weather has warmed up instructions or the following:
1.If you choose to plant out in a permanent location right away and your day time temperatures are in the mid-70’s or higher; mulch the soil surface well after planting, irrigate regularly to keep the soil evenly moist, not soppy wet, and provide shade until the plants are well-established. Warmer air temperatures encourage faster leaf and shoot growth than root growth, creating an imbalance between supply and demand in the plant. Shade helps to reduce the water needs of the plant and give the root system time to grow and catch up with the water demands of the top of the plant.
2.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.
3.Plant your new plants in containers, or if you received potted plants put them in a somewhat larger container. Maintain them in a protected location, and plant in their permanent location in the fall when the worst of the summer heat has passed.