December Growing Tips
TIMELY TIPS FROM RAINTREE HORTICULTURIST THERESA KNUTSEN
The following subjects are covered in the December Growing Tips:
Look for my second of three installments of tips on ordering new plants in the Frequently Asked section at the end of this newsletter. You will also find information on: how to transplant and planting recommendations for our customers living in warm winter locations; winter pruning and peach leaf curl disease control; grafting tips for those of you wanting to create your own trees; and winter care of potted plants.
Where temperatures have not yet fallen to hard winter lows, December is an excellent time to dig and transplant dormant plants that are not yet in their permanent locations, or are in the wrong place. You can also continue planting dormant nursery stock provided the ground is not frozen or covered with snow and there will be about 4 weeks or so before they will experience hard freeze.
When you transplant, the plant you are digging and moving should be fully dormant, or nearly so. Make sure the root system is well watered a week or so before digging it up. Get as much of the root system as you reasonably can and water well after you re-plant. If you need to move a larger tree, plan to take a little more time with the process. Start in October, when the plant is nearly dormant. Dig straight down into the ground 12-18”deep, to sever the roots, along 1/3 of the planned root ball perimeter. In November dig along the next third of the perimeter. In December dig the final third along the perimeter and under the root-ball so you can lift the tree out. Carefully reset it in its new location and water in well. A little bone meal, or slow-release phosphorous source mixed with the back fill is beneficial, otherwise do not apply fertilizers. If you did not add mycorrhizal fungi to the soil when you originally planted, adding some now will be helpful. Finish your planting by applying a ½ inch layer of compost over the surface, then 3-4” of coarse material, keeping the mulch at least 2” away from the trunk (Raintree Plant Owners Manual pg 4).
Some of you may live in locations in which December and January are the optimal time for planting. We ship potted plants in shippable sized containers in the fall, but our selection is limited. Sometimes we have to stop shipping potted plants East of the Cascades before the end of November due to cold temperatures here, or across the country. We will continue to ship potted plants along the west coast, weather permitting. In addition, we do not ship plants East of the Cascades December through mid-to-late January to avoid freeze injury to plants as they travel across the country (we have no idea what the actual route could be). During this time we are also taking care of the bare root plants as they finally come out of the ground and we organize and store them.
If we can not get plants to you at your optimal planting time you could follow one of these approaches with plants we send to you in February:
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. Another method that may help the trees stay cool is to paint the dormant trees with a 50/50 mixture of interior white latex paint and water, then plant. If you brush the paint on apply with an upward stroke, to avoid damaging buds.
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, 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.
Once your trees, shrubs, and vines have achieved full dormancy (leaves on the ground for deciduous plants, no tender new growth buds visible on evergreen plants) you can begin dormant season pruning. If you tend to experience a lot of freeze, wind, or fungal damage during the more severe part of winter it might be best to leave the pruning for later in the winter, after the majority of the damage has occurred. Delay pruning stone fruits (cherry, peach, apricot, nectarine, and plum) until early spring, when the buds begin to swell, to minimize fungal infections in your pruning cuts. Delay pruning of Asian pears that are susceptible to pseudomonas disease until after the spring rains have ended, to minimize infection opportunity. In the Pacific Northwest that generally means summer or early fall.
If you have not yet done so, cut out old dead fruited canes from blackberries, raspberries, and related hybrids and tie in the new canes for next year. Cut everbearing raspberries and blackberries to the ground after all the fruit has been picked. New canes will grow next spring and produce fruit in the fall. You could also cut the everbearing canes to just below where they fruited this fall, leaving the lower portion of the cane to provide you with a small crop next summer.
Peach Leaf Curl Control: One of the more significant fungal diseases in the Pacific Northwest on peaches is Peach Leaf Curl. Once the chill requirement for the peach tree has been met, the sealed bud scales “unzip” (the seal releases, but you will not be able to see any change), leaving them vulnerable to peach leaf curl infection. Peach leaf curl infections can only be prevented, control treatments are ineffective.
There are two primary methods of treatment. One is to apply lime sulfer fungicide, starting when the bud scales have released. In the Pacific Northwest apply three times, at three week intervals, starting late December or early January, (Raintree Plant Owners Manual pg 17). It is best to apply on a dry day. Time tables for treatment vary in different parts of the country; contact the co-operative extension office in your location for recommendations. If you are growing low chill varieties of peach (such as the genetic dwarf peaches) in a high chill hour accumulation location, such as the Pacific Northwest, you may need to start your spray program in November and add an additional application.
Another prevention method is to keep the stems of the tree dry. The peach leaf curl organism needs moisture on the stems to germinate and grow; keeping the stems dry prevents that growth. Put plastic (opaque or clear) over the tree, with supports to keep the plastic off the stems (condensation will make the stems wet), after the tree has gone dormant and before the buds have “unzipped”. Or train a tree against a wall under an eave where rain won’t contact the stems. Genetic dwarf peaches can be grown permanently in a container. Move the potted tree to a rain protected location, such as a carport or covered patio, during the cool wet infection period. An additional benefit to keeping the stems dry is you prevent other types of fungal disease infections that would normally also affect peach trees, such as brown rot or coryneum blight.
The easiest method would be to select a cultivar of peach that has some degree of resistance to peach leaf curl. Then you may only to need to spray during the first few years. Find variety options on our web site, in the curl resistant list in the peach section, or in our catalog.
After winter storms, inspect trees and bushes for damage. Make clean cuts where there are ragged tears and breaks to minimize fungal infection opportunity. Current recommendations indicate to only use tree seal products on larger wounds (greater than 12") and avoid treating the outside inch or so, to avoid compromising the regrowth of the cambium layer. Prop fallen trees back up, if the root system has not been damaged by snow, ice, freezing temperatures, etc. Dig a hole under the area where the root system was pulled up, so it has a place to go back in to as you stand the tree up. If there is a lot of root damage you may need to trim the top a bit to rebalance the tree. It is important that you only make thinning cuts though, terminal buds will tell the root system to start growing in the spring, a much needed message for a damaged root system. Keep the tree supported for the next year or two to ensure the root system has reestablished.
If you are planning to do some grafting this winter or next spring, December –February is the time to collect scion wood, from fully dormant trees. 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 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. 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.
Finally, the lemons on your Meyer’s Lemon Tree that set last February are starting to swell and look like they will really ripen (next month). Continue monitoring for insect populations, early detection and treatment will keep those pests under control. Keep your lemon trees flowering and fruiting periodically throughout the year by protecting them from night temperatures below 50° F. Indoor humidity will be dropping now as heating needs increase. Keep humidity up around your citrus trees by misting daily, locating an indoor water feature near by, or placing a tray of pebbles that holds water under your plants for evaporation. The pebbles are to keep the container elevated so water doesn’t wick back up into the pot. Water citrus plants thoroughly as needed, allowing pots to dry out well between each watering. As indoor plants go dormant their water needs decrease, this is the easiest time of year to over water and cause damage to the roots.
Repotting is best done when plants are dormant. You can move your plant up to the next size container, or keep it in the same pot. In either case it is important to loosen the root ball and remove circling roots to encourage healthy new root growth activity next year. Gently remove the plant from its container. Use a knife to cut away the bottom and sides of the soil/root ball; ½ to 1 inch is enough if you are moving the plant to a larger container, 1-4 inches off the bottom and ½ that amount off the sides works well if you are keeping it in the same container. The larger the container the more you want to remove. Then use a pointed blunt object (I use my pruning shears, closed) to poke into the root ball and loosen it up a bitif it is very tight. Put fresh potting mix in the bottom of the container, enough to replace the volume you removed from the bottom of the soil ball, or to bring the top of the soil ball to ½-1 inch below the rim of the pot. Set the plant in the container, add fresh soil around the sides, jiggle the pot a bit to settle the soil, and water in well.
It can be hard to determine when evergreen plants, like citrus, are dormant, since they don’t lose their leaves. For these plants, dormancy is a rest period during which they stop actively growing. Look at the shoot tips. Buds at the shoot tips will stop making new leaves and the shoots themselves will be firm, not flexible and tender. Sometimes the rest period only lasts a few weeks, so be sure to take care of the re-potting as soon as you notice they are dormant, generally late December to early January.
If you still have hardy potted plants you are keeping outside that are not heeled in, remember to pay attention to temperature predictions. If overnight temperatures are expected to drop to the low 20’s, or daytime temperatures will remain below freezing, you need to protect the roots of those plants, which are generally not as cold hardy as their tops. Bring them in to a cool (35-40° F) location, or bury the pots to the rim in loose well-drained material. Return them back outdoors when the temperatures have moderated, until the next cold spell, to keep those plants dormant.
Are there Medlar or persimmon fruit still on your trees? The freezing temperatures of December can bring out the sweet flavor in these fruit. Try them and see…. Those of us living in the Pacific Northwest and other mild winter areas could try putting persimmon fruit in the freezer for a few days; I’m told that can help bring out the flavor also.
After the holidays, as you begin browsing through a new season’s worth of catalogs, review how well your irrigation system worked (or didn’t work) for you this last year. Take stock of what parts you have on hand and what you need, now is an excellent time to plan for the next growing season.
FREQUENTLY ASKED QUESTIONS:
These are questions we are regularly asked by customers who are trying to figure out which varieties they want to order. Select Growing Info on our home page, then scroll down to find the article 'Choosing which plants will work for you', to see what is not covered below.
Our standard answer is 2-3 years to first fruit. In some cases your trees may arrive with flower buds and be apparently ready to produce fruit. It is best, however, to remove any fruit that sets in the first two years. This allows the plant to focus its available energy on establishing a strong root system, trunk, and primary branches. After two years fruit trees are generally established well enough to continue growing strong while producing a moderate crop of fruit. Expect your tree to need another 2-3 years to produce heavier crops.
There are, of course, some exceptions. Newly planted fruit trees that are allowed to mature fruit in their first year might not initiate fruit buds again for several years, as they make up for the excessive energy drain making fruit in that first year. Small fruited cherries and plums can produce small crops right away without compromising growth, thin the fruit if a lot of fruit sets. Finicky persimmons may start fruiting between 3 and 7 years after planting, or more. To encourage earlier production in your persimmon feed your tree with a fertilizer that is high in Nitrogen and Iron the first few years. If you live near enough to Raintree Nursery you could also consider taking home more mature ready to bear fruit trees we offer each year. Allow the trees to re-establish for one year and they will be ready to produce nice crops of fruit for you.
How about first fruit for berries? Floricane blackberries and raspberries produce fruit in the second growing season of the cane; primocane berries produce fruit in the fall of the first growing season of the cane. It will take 2-3 years for the root system to be fully established and your planting ready to produce full crops.
Blueberries tend to be slow growing plants, again, 2-3 years is a reasonable time expectation to harvest good quantities, with full production needing another 2-4 years. There will often be some berry production in the first year, thin the fruit if a lot of fruit set, otherwise it is OK to allow those fruit to mature.
Day-neutral (everbearing) Strawberries will produce a good crop the first year when planted early enough to establish the roots, generally by mid-April, or early spring in your location. Remove blossoms until you have 3-5 mature leaves on the plant, then you can allow fruit to set. June-bearing varieties will also bloom in the first year. Remove those blossoms and position runners to fill in your row and you will be rewarded with a heavy crop in the second year.
Unusual Fruits and Berries, such as Goumi, Goji, Sea Berry, Currants, Gooseberries, and Honeyberries tend to start producing fruit at 2-3 years, or when the plants are established.
POLLINATION CHARTS are found in the catalog, with each major type of fruit, or on our web site, click on GROWING INFO in the top tool bar. If there is not a chart for the fruit you are looking at, there should be information in the How to Grow section for that fruit in the catalog or the growers guide for that type of fruit on our web site. Most of our pollination charts are in graph form. The varieties will be in approximate bloom time order, earliest at the top of the chart, latest at the bottom, reading down the left side. Find the variety you are interested in on the left side and read across the chart from that variety. A potential pollinizer from the list across the top of the chart will line up above a white square, a red square indicates pollination will not work, a green square indicates the variety is self fertile.
The apple pollination chart has grown too big to fit in a graph, so we are using columns, divided into 5 bloom seasons. A particular variety will pollinate another in the same bloom season, or the season before or after. If the variety is written in red it has a triploid pollen grain, which will not pollinate other apples. If the variety is written in green it is considered reliably self-fertile.
Our pollination charts are meant to be a guide line. While the bloom order stays generally similar in different parts of the country and in different years, the actual bloom dates change from year to year depending on the weather.
You may find that varieties we indicate need a pollinizer are considered self-fertile by other sources. That may be true, depending on where they are located. Whether it will also be true for you depends on whether you are in a similar location. In the Pacific Northwest, our long cool wet springs interfere with pollination enough that the presence of a second variety is often needed to ensure good fruit set.
THE APPLE HEIGHT AND SPACING CHART in the catalog will help you determine the approximate height you can readily maintain your tree with pruning, and the minimum recommended spacing between the trees. Some varieties are more vigorous than others; different rootstocks also have an effect on size. The most vigorous varieties grafted onto the EMLA 26 rootstock can grow to about 18-24’ tall and wide, but can be readily maintained at 12-14’ tall and wide. The least vigorous varieties grafted onto the M27 rootstock might grow to 6’ or so, but are readily maintained at 4’. Except for the columnar apples, apple trees tend to have a rounded shape, so height and width will be similar. The minimum spacing we indicate is also the height you can readily maintain the tree at. If you want to maintain your tree at a taller height than we have indicated, then you need to increase the spacing the same amount.
RIPENING ORDER information is provided for the major fruits we offer in the catalog and in GROWING INFO found on our home page. Remember that bloom time order and ripening order will be different. An early blooming apple will not necessarily ripen early. As you select your variety choices to harvest at different times remember to cross check that pollination will also work.
As you look about your winter landscape, are there bare spots that need some sprucing up with winter interest? Consider an evergreen choice such as Sunshine (#E285) or Misty (#E250) blueberries to provide year round color and delicious berries, or perhaps Wintergreen (#G360) to cover the ground with mounds of glossy evergreen leaves dotted with persistent red wintergreen flavored berries will better suit your situation. The bright red stems of Cornus stolonifera (Red Osier Dogwood #M120) stand out against snow and evergreen foliage. Winter blossoms can offset the winter doldrums, such as Red Dragon Contorted Filbert (#K031) with its yellow catkins hanging from crooked branches January and February each winter. Some trees provide interesting structure with their winter silhouette. The Medlar with it's somewhat eratic growth habit, Japanese plums with their reaching, spreading shape, weeping mulberry, or maybe contorted willow (with winter catkins as bonus). Click on GROWING INFO on our home page, then scroll down to the ‘Right Plant Right Place’ chart which will help you explore plant choices for particular attributes, such as winter interest, shade tolerant, wet feet tolerant, for the hummingbirds, etc..