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Search Results for ' Failure to flower'

PAL Questions: 13 - Garden Tools:

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Keywords: Failure to flower, Frost, Rhododendron, Master gardeners

PAL Question:

This is the second year in a row that my rhododendron Blue Peter has flower buds but they are dry and somewhat dark and have no flowers at all. These buds are easy to deadhead. Can you help me salvage this rhododendron, which is very old, and beautiful when it blooms?

View Answer:

In order to get an accurate diagnosis you will need to take a sample of your plant (including both healthy and affected parts if possible) to a Master Gardener clinic. If they do not know what it is, ask them to send the sample to the pathology laboratory in Puyallup. It is best to go through Master Gardeners first so you will not be charged. If you send the sample yourself there will be a fee.

Meanwhile, several sources mention frost, drought, and "bud-blast" (unlikely in the Pacific Northwest) as potential causes of bud failure. Damaged flower buds and poor bud set: It is always most disappointing when fat, healthy looking flower buds either fail to open at all or only open a percentage of their buds, the rest being black and dead. Some rhododendrons regularly abort some or even all of their buds for no apparent reason. This may be due in some cases to a deficiency, perhaps magnesium, or to drought…reports from various places give mixed results from applying magnesium (usually as Epsom salts)... By far the most usual cause of bud damage is frost. Flower buds are invariably less hardy than the rest of the plant so a really hard winter is sure to cause losses to flower buds. Early autumn frosts can damage buds that are not fully hardened off. This is a very annoying type of damage that may be overlooked and may not be noticed until the buds attempt to open in spring. Rhododendrons vary greatly in their ability to harden up enough to withstand early frost. In areas very prone to spring frosts, it is better to avoid growing plants that always burst into growth at the first sign of spring. Plants that frequently loose their first growth flush (and sometimes even their second) are liable to become stunted and rarely flower.

Source: The Cultivation of Rhododendrons, by P. Cox, 1993, p. 244.

Season Spring
Date 2006-10-26
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Keywords: Failure to flower, Hydrangea

PAL Question:

I have two Hydrangeas growing up the side of my house in a northeastern exposure. This will be their 4th year. Leaf growth is robust... flower growth almost non-existent (on one of the shrubs, one bloom last year; one forming this year). What can I do to encourage bloom or should I start over?

View Answer:

According to the Hydrangeas! Hydrangeas! website, there could be several reasons why yours are not blooming well. Check out their page, “Why Won’t My Hydrangeas Bloom?”

There is another useful resource that may be of help. Try Why Plants Fail to Bloom, by Leonard P. Perry, a professor at the University of Vermont Extension. Perry suggests there are five possible reasons: Age, Temperature, Alternate Flowering, Light, Nutrition and Pruning.

In addition, I consulted two books on hydrangeas. Both mentioned that Hydrangea anomala subsp. petiolaris can take time to bloom. According to Michael A. Dirr’s Hydrangeas for American Gardens, “Time is [the climbing hydrangea’s] biggest ally.” That is, once it gets established, there is no stopping it.
Michael A Dirr. Hydrangeas for American Gardens. Timber Press, 2004. p. 24.

Toni Lawson-Hall’s Hydrangeas: A Gardener’s Guide also says that Hydrangea anomala subsp. petiolaris “grows well on north-facing walls but takes a while to get established.”
Toni Lawson-Hall. Hydrangeas: A Gardener’s Guide. 1995. p. 81.

You are probably wondering how long “a while” is. Alas, I was unable to locate a specific timeframe for when you might expect those gorgeous blooms to start, but from what I can gather, time may help.

Season All Season
Date 2006-10-26
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Keywords: Failure to flower, Syringa

PAL Question:

I have a lilac bush given to me as a gift 13 years ago. I don't know the variety but the leaves look slightly different from the common lilacs I see. This bush has healthy looking leaves and while it has slowly put on growth over the 13 years it has never bloomed. I have tried adding ashes to the soil to make it more alkaline but nothing seems to work. What is the problem and how can I get this bush to bloom?

View Answer:

There are several reasons lilacs may fail to flower. Here is an excerpt from North Dakota State University Extension horticulturist Ron Smith in answer to a question similar to yours:

Lilacs fail to flower because of insufficient sunlight, planted too deeply, too much nitrogen, improper pruning or winterkill of the flower buds. You said the lilacs get plenty of sunlight, but unless you used a lawn fertilizer to provide nutrients, it isn't likely too much nitrogen is the problem. If you planted too deeply, pull some of the soil back so the top of the roots are slightly exposed. If you pruned in July, then doing so removed the flower buds for the next growing season. If winter killed the flower buds, then hope for milder winters or purchase hardier lilacs.

Colorado State University Extension's article, "Renewing Lilacs," offers other suggestions, such as late freezes, decreasing sunlight, and pest problems.

Sunset's Western Garden Book (2001 ed.) says that annual pruning is needed for optimal flower production. Most lilacs bloom on wood formed the previous year, so they should be pruned just after flowering. Remove the spent blooms and cut back to a pair of leaves. There are a few lilacs which bloom on new growth, so it might be useful to know exactly what type of lilac you have. You could bring in photos and samples to our Herbarium for identification.

Season All Season
Date 2007-05-09
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Keywords: Failure to flower, Trachelospermum

PAL Question:

I bought an established, white star jasmine perennial vine one year ago. I was told I could plant it in an extremely large pot and expect to enjoy blooms for about 3 years, but it has not bloomed, nor does it have any buds. It has no pests or blight of any kind. It gets full sun in the morning and partial during the day, and full again in late afternoon. It has always had sufficient water. What's wrong? When do they normally bloom? Was I given inaccurate information?

View Answer:

I am assuming the star jasmine is Trachelospermum jasminoides, as shown in this image from Missouri Botanical Garden.

Failure to flower can be due to a number of causes, as described in this link from University of Vermont Extension.

My top guesses for what may be causing the lack of flowers would be exposure to severe cold in the winter, or over-fertilizing with a nitrogen-heavy fertilizer. The light exposure you describe sounds fine for this plant. In the Pacific Northwest, it flowers mainly from spring to early summer. This link to a Seattle garden writer's site has cultural information appropriate for this region (I don't know where you are writing from).

Season All Season
Date 2007-08-29
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Keywords: Failure to flower, Hydrangea

PAL Question:

Help! We live in North Bend and have several Hydrangeas. I have a large Annabelle that has never bloomed properly. Is there some special care or fertilizing that I can do to encourage normal blooms on these plants?

View Answer:

Here is some information on how to improve flowering, from the U.S. National Arboretum:

Excerpt:

There are three possibilities for lack of flowering among the hydrangea species. The first two – too much shade and improper pruning – apply to all hydrangeas, while the other – weather-related damage to flower buds – applies primarily to the bigleaf hydrangea.

While most Hydrangea species benefit from some shade, too much shade can reduce flowering. This is particularly true of panicle hydrangea, which is the one Hydrangea species that grows well in full sun. If you have a hydrangea that used to bloom well but now flowers only sparsely, evaluate whether the growth of nearby trees has reduced the amount of light that reaches the hydrangea. If so, you may want to consider moving the hydrangea to a sunnier location.

Improper pruning can also reduce flowering in Hydrangea. Since bigleaf and oakleaf hydrangeas flower on previous year’s growth, potential flowers buds would be removed if the plants were pruned in fall, winter or spring. Panicle and smooth hydrangea flower on this year’s growth, so pruning them in early summer would reduce or eliminate flowering for that year.

The most common reason for lack of flowering in the bigleaf hydrangea is unfavorable weather. Most H. macrophylla cultivars flower primarily on previous year’s growth. Weather conditions that damage aboveground parts of the plant can reduce flowering. Damaging weather conditions include early fall freezes that occur before the plant is completely dormant, extremely low winter temperatures, and late spring freezes that occur after the plant has broken dormancy. In USDA Cold Hardiness zone 6 and warmer, which is the recommended growing area for H. macrophylla, the most common of these unfavorable weather events is late spring freezes that damage tender new growth. This is particularly true in the southeastern U.S., where "see-saw" temperatures are very common in the spring.

Bigleaf hydrangea responds quickly to warm temperatures in late winter and early spring by breaking dormancy and producing new leaves. Unfortunately, these spells of warm weather are often followed by periods in which temperatures reach well below freezing. The severity of the damage caused by these freezes depends on how many of the buds had broken dormancy. If a substantial portion of the buds on a stem were actively growing, the whole branch may die. For some cultivars, the loss of the aboveground part of the plant will completely eliminate flowering the following summer. The plant will produce new buds from the base of the stems, but stems produced from these buds will not flower in these cultivars.

Season All Season
Date 2008-01-24
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Keywords: Failure to flower, Stachys, Pruning shrubs, Leycesteria

PAL Question:

I have a question about cutting back plants. I have some non-flowering lamb's ear that is looking quite scraggly. How far back do I cut these, and when?

Also, how far back should I cut my Himalayan honeysuckle? We planted it 2 years ago, and last summer it got 5 feet high!

Also, last year my Hebe plants did not flower. We have Hebe anomala purpurea 'Nana'. I have recently checked the tags they came with, and it doesn't mention that it flowers. Is this a non-flowering Hebe? Although the shrubs are lovely, I was hoping for the type that flowers. If we decide to move them, when would be the best time to transplant them?

View Answer:

Yes, Stachys (lamb's ears) can look pretty ragged after winter. I'm guessing you are growing Stachys byzantina 'Silver Carpet' or a similar cultivar, which doesn't flower. If you look closely, you should see signs of new growth. I would suggest cutting back all the tattered or dried leaves as far as you are able, without injuring new growth. March is a good time to divide the plant if you like. (I have shared this plant many times and moved clumps to new locations. It is quite tough, and will transplant easily.)

Himalayan honeysuckle, Leycesteria formosa, can be cut back to the ground (or within a few inches of the ground) in late winter or early spring,according to Sunset Western Garden Book. The website of Rainyside Gardeners (a Northwest site) has a useful page on Leycesteria formosa.

According to Hebes: A Guide to Species, Hybrids, and Allied Genera by Lawrie Metcalf (Timber Press, 2006), Hebe anomala 'Purpurea' is a synonym for Hebe odora 'Purpurea' which is supposed to have a lot of flowers. He doesn't mention the dwarf variety, 'Nana,' but I assume it would have similar attributes. Even with the nomenclature confusion, there seems to be some consensus about the floriferous qualities of the plant: Douglas Chalk's Hebes & Parahebes (Christopher Helm, 1988) lists Hebe 'Anomala' as a cultivar of Hebe odora, and he too says it has lots of flowers. Are your Hebes getting enough sun? Some Hebes will flower in partly shady sites, but the flowering will be diminished. Could they have been pruned accidentally, just before flowering? Another possibility is that the plants are not mature enough to flower. The Metcalf book mentions a few species which can take years to produce flowers. He also says that flowers are enhanced by chilling followed by warmth, over a period of about 12 weeks. The number of hours of daylight to which the plants are exposed is also a factor. As far as transplanting, doing it in March should be fine. It isn't too hot, and we are likely to have the occasional rain,but you should still water well when you first move them.

Season All Season
Date 2008-04-11
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Keywords: Failure to flower, Pyrus, Corylus, Prunus

PAL Question:

I planted numerous fruit trees about 7 years ago. These included almond, pear, apple, hazelnut, and plum. The almond and apple trees have done really well.

The pear, plum, and hazelnut trees have never even bloomed, let alone borne fruit. Am I doing something wrong or do I just need to be a little more patient?

View Answer:

All of your trees should be mature enough to flower and bear fruit, given the right conditions. There are many potential causes of failure to flower. Are your trees that have not flowered in a location that receives high nitrogen fertilizer (such as near a lawn)? This would lead to lots of leafy growth at the expense of flowers. Cold winter weather can also damage buds and lead to no flowers.

The lack of fruit could be due to lack of pollination in addition to the causes listed above. Do you have two or more pears (Pyrus) and hazelnuts (Corylus)? Is your plum (Prunus) a variety that needs a pollenizer, or is it self-fertile? Raintree Nursery has information on flowering and fruiting for Corylus that says"Two different varieties or seedlings of similar flowering period," are needed, and that "European Filbert flowers winterkill at -15 F. Others are hardier."

Spokane County Extension has fruit pollination charts, and there is an example from Burnt Ridge Nursery for European pears. At the very bottom of the webpage linked below, you can find Raintree Nursery's pollination charts for various fruits and nuts.

General information from University of Vermont Extension on failure to flower and failure to bear fruit from Washington State University Extension.

Season All Season
Date 2008-04-11
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Keywords: Failure to flower, Helleborus, Transplanting

PAL Question:

One of my hellebores did not flower this year. I think the spot became too sunny with removal of a bush. When can I transplant it?

View Answer:

Hellebores should not have a problem with sun. They will do fine with a certain amount of shade in the summer, but according to C. Colston Burrell and Judith Knott Tyler's book, Hellebores: A Comprehensive Guide (Timber Press, 2006), "the more sun hellebores receive, especially in spring while the foliage is expanding, the fuller the plants grow and the more prolifically they bloom. Light to partial shade is best for most species and hybrids. The stemmed species such as Corsican hellebore are likely to flop in shade, and they tolerate full sun." The authors also say that it takes 2 to 3 years for plants to bloom at full capacity, so if these are new Hellebores, perhaps they are still getting settled. After 2-3 years, the number of flowering stems should increase.

Have you removed last year's leafy growth? Perhaps if you do this, the plants will invest their energy in the flower stalks. The Burrell and Tyler book says that the winter foliage can cause problems if it becomes entangled with emerging flower scapes. Winter foliage can also attract aphids, which will drain the plant's energy as well. Be careful when removing the old leaves, as the sap can cause skin irritation.

If you wish to move the plants, I would suggest waiting until summer or fall when they are dormant. Moving them might mean you won't get flowers for a while, until the plants settle into new surroundings.

When transplanting, Burrell and Taylor indicate that "Small plants that are not root-bound recover from transplanting fairly rapidly. Once planted, sparse to moderate blooming occurs the following season. It takes two to three years for plants to reach full steam." p. 162.

Also, be sure that if you move it you replant it at the same depth it was growing at before, since deep planting can prevent flowering:

"Hellebores buried with their crowns in the soil exhibit inferor flowering, if they bloom at all, though they continue to produce foliage. The crowns produce short vegetative stems that raise the leaf buds up to the soil surface, but in our experience, when buried alive seldom flower." p.167

It is always hard to know the precise reason a plant fails to produce flowers, as there are many possible causes. I recommend removing the winter leaves, and waiting to see if the flowers return next year. I would not move the plants just yet, unless the site has become scorchingly hot.

Season All Season
Date 2008-04-12
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Keywords: Failure to flower, Magnolia grandiflora, Frost

PAL Question:

I have a Magnolia grandiflora 'Little Gem' - I've noticed it is not flowering very much any more and when it does produce flower buds, they turn brown and start to die before they have fully bloomed. Can you tell me what causes this and what I can do to keep this from happening. The tree itself seems quite healthy and is growing very well.

View Answer:

There are a number of reasons that plants may fail to flower, and it may be difficult to pinpoint precisely why for your Magnolia grandiflora.

If this is a newly planted Magnolia, it may be too young to flower. Magnolias are somewhat notorious for being slow to flower.

Sometimes, cold temperatures kill off flower buds. This could cause bud browning and failure to flower. Magnolias can be quite sensitive to cold temperatures and to wind, in particular (see the picture of another Magnolia species with frost damaged flowers here In some cases, frost damage can be severe enough that the flower buds die entirely.

There is a chance that the M. grandiflora's failure to flower could be related to fertilizers, as well [source: This Old House website]. Making more phosphorus and micronutrients available to the tree, or avoiding adding nitrogen, can help balance this out. Rankin's book says that a Magnolia which is mulched once or twice a year does not need supplemental fertilizer, and adding it can encourage excessive vegetative growth at the expense of flowers. When there is a high quantity of nitrogen, plants tend to grow leaves rather than flowers. For example, flowering trees planted in lawns that are heavily fertilized with nitrogen may flower much less or not at all.

Finally, M. grandiflora tends to need a fair amount of sun in order to blossom. On one gardening web page, I found an anecdote where the author talks about a M. grandiflora tree they own, half of which is shaded and flowerless, and the other half of which gets sun and flowers profusely. According to Magnolias: A Care Manual by Graham Rankin (Laurel Glen, 1999), any Magnolia planted in heavy shade will flower very weakly at best.

Season All Season
Date 2008-05-28
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Keywords: Embothrium coccineum, Failure to flower

PAL Question:

I have a Chilean Fire tree (Embothrium) that I planted about four years ago. It has grown rapidly to about seven feet tall. It has not yet bloomed. At what size or age does this tree bloom? Does it require some encouragement, like root pruning, to get it to bloom? I have not fertilized it because I have read in at least two sources that these plants should not be fertilized.

View Answer:

There are many reasons a plant may fail to flower, immaturity being one of them. You are correct to avoid over-fertilization, as that is often a cause of lack of flowers. Another cause is unusually cold weather.

I found an article by Roy Lancaster on Embothrium coccineum in Gardens Illustrated, May 2005. He mentions that if the tree is planted in a somewhat shady site, it will not flower as prolifically. Acid soil which is moist but well-drained, and a sunny but sheltered spot are ideal.

There is a discussion of the problem of Embothrium’s failure to flower on the NPR Talking Plants website in 2007 (formerly hosted by Portland gardener Ketzel Levine). It appears that this is not an uncommon problem. Here is an excerpt, from a gardener responding to Levine's complaint about the lack of flowers:
"Many have found Embothrium to be a slow bloomer. It is a polymorphous plant in many ways: some are evergreen, some deciduous, some are trees, some are shrubs. Some bloom in a 1-gallon container, others need to put on some size first.
"The danger of phosphorus toxicity rules out some of the usual bloom-stimulation therapies using fertilizer. Provided that it's getting enough sun exposure, I'd say just sit tight and give it a few more years. If you've been watering it on a consistent basis all summer, hold back and let it dry out for a few weeks between good soakings.
"If you get really desperate and are contemplating its removal, you might first take a propane torch and try burning the leaves and twigs off when autumn comes (don't scorch the bark on major limbs). I know that sounds a bit absurd, but some plants respond to environmental adversity by blooming, and the fire trick has been known to work on some other proteaceous flora. From the plant's point of view, why expend the energy of going into a reproductive cycle when everything's fine and there's no threat to survival? Give 'em something to worry about."

If you feel daring or desperate, I suppose you could try the blowtorch approach, or you could make sure to provide the ideal conditions, and wait patiently. Levine, like you, thought of root-pruning her Embothrium to induce flowering. You could try to contact her and ask if she tried it or the fire method, and if either worked.

Season All Season
Date 2008-06-04
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Keywords: Schlumbergera, Failure to flower

PAL Question:

I have a Christmas cactus that is very healthy and blossomed profusely last November. I attempted to duplicate the same environment that the cactus had a year ago, but that wasn't possible, and it didn't produce a single blossom. The foliage is glossy with health, but I don't water the plant for a couple of months in the fall to stress it a bit to encourage blossoms.

I put the cactus in our dark, cool garage for the month of October just as I did last year. When I returned the cactus back upstairs in our house to its usual south window spot and watered it, it gave no blossoms this year. Why?

I've looked online and in books for info on encouraging bloom, but I haven't come across much about Christmas cactus. The cactus gets direct southern light all year except for the month when it is in the garage, which has only a north window. Is lighting the problem? The garage is about 65 degrees F, same as last year, so I'm thinking the temperature isn't part of the problem, or is it?

View Answer:

There may be a combination of factors involved in the lack of flowers on your plant. If it is a young plant, it may have needed repotting. It may not have been in the dark, cool environment quite long enough or soon enough. According to The Complete Houseplant Survival Manual by Barbara Pleasant (Storey Publishing, 2005), the ideal conditions for Christmas cactus (Schlumbergera hybrids) are as follows:

  • Bright light from late spring to fall, and moderate light from late winter to early spring
  • 65 to 80 degrees from late spring to late summer, and 50 to 65 degrees during fall and winter
  • Balanced fertilizer every 2 weeks from spring through summer, and monthly in fall and winter
  • From spring through fall, keep soil lightly moist but in winter, it should nearly dry out before watering sparingly
  • Repot young plants each summer; older plants can be repotted every 2 to 3 years
  • Plants tend to have a lifespan of 5 to 6 years, but you can propagate them from stem cuttings
  • Clemson University Extension has additional information on growing Schlumbergera. Here is an excerpt:
    "The secret of good flower production involves temperature and dark (photoperiod) control. To flower, plants need bright light; night temperatures between 55-65; long nights--13 hours or more of continuous darkness each day is required before flowering will occur. Long nights should be started about the middle of September and continued for 8 weeks."

    Season All Season
    Date 2008-12-11
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    Keywords: photoperiodism, Kalanchoe, Failure to flower, Succulent plants, House plants

    PAL Question:

    Why do my house plants stop flowering after I bring them home? They are by a bright, sunny window. I bought Kalanchoe in 4 colors, and none flower any more.

    View Answer:

    Can you tell me if you feed the houseplants anything? Sometimes plants (indoors or outdoors) which are given a fertilizer that is high in nitrogen will produce a lot of leafy growth at the expense of flowers.

    Make certain that you are providing ideal conditions for growing Kalanchoe. According to Barbara Pleasant's The Complete Houseplant Survival Guide (Storey, 2005), Kalanchoe grown indoors needs bright direct sunlight, and warm temperatures (70-90 degrees) from late spring to early fall. In fall and winter, it requires 50-70 degrees. It sould not receive any fertilizer from late winter to early spring, and in winter, let soil dry out between light waterings. More importantly, Kalanchoe responds to changes in its exposure to light, which is referred to as photoperiodism. Pleasant says that "before a kalanchoe will make buds, it must be exposed to a series of long, sunny days followed by at least 2 weeks of short days, less than 12 hours long. This is easy enough to accomplish by placing plants outside in summer and then bringing them indoors in late fall, just before nighttime temperatures drop below about 40 degrees. After you bring the plant in, keep it in a room where no lights used at night. When brought into bloom naturally, kalanchoes flower in January and February. To speed up the schedule, cover the plants with a box for 14 hours each night for 14 consecutive days. Blooms will appear about 6 weeks later. Snip off bloom-bearing branches after the flowers fade."

    Season All Season
    Date 2010-08-26
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    Keywords: Philadelphus, Failure to flower, Pruning shrubs, Fertilizers

    PAL Question:

    I just bought a house with a garden which has good bones, but has been untended for a long time. I believe the garden has 4 Philadelphus X virginalis 'Minnesota Snowflake' plants. They are deciduous in the winter, and they have greened up nicely in the summer. They are about 6 feet tall. On the 4 plants, this first summer, I've only seen 2 flowers. Can these shrubs be salvaged by using a blooming (high in phosphorus) fertilizer? Or do they need something else?

    View Answer:

    The three things I would ask about Philadelphus with few flowers:

    • Are they in full sun? (Sun is needed for best flowering results.)
    • Have they been pruned and, if so, when? (Pruning is best done in late summer, after flowering.)
    • Are they growing near a lawn or other area which receives fertilizer that is higher in Nitrogen (N) than Phosphorus (P) or Potassium (K)?

    I would recommend that you test the soil before embarking on a plan of fertilization, unless you are adding a mulch such as compost, which releases its nutrients slowly. Philadelphus is usually considered a light feeder (i.e., it doesn't require a lot of supplemental fertilizer).

    As far as a future pruning regime for the shrubs, Jacqueline Heriteau's Complete Trees, Shrubs & Hedges: Secrets for Selection and Care (2005) says that Philadelphus "blooms on the previous year's growth. A light annual pruning of older branches right after flowering keeps mock orange shapely and productive. Branches more than five years old should be removed in winter or early spring."

    Season All Season
    Date 2011-07-12
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June 24 2013 12:55:25