Reviving Philadelphus

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?

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.”

Failure to flower, Fertilizers, Philadelphus, Pruning shrubs

encouraging Christmas cactus to bloom

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?

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.”

on pruning lamb’s ear and Himalayan honeysuckle

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?

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.

encouraging Kalanchoe to bloom

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.

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 should 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.”

fruit trees and lack of fruits

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?

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.”

Oregon State University Extension has fruit pollination charts, and there is an example from Burnt Ridge Nursery for European pears.

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

Climbing hydrangeas won’t bloom

I have had a climbing hydrangea for 4 years – but it has never bloomed. It is growing but does not produce any buds. It gets full sun and is in good soil. What can I do so it will produce blossoms?

I looked in a few books (including Trees and Shrubs for Pacific Northwest Gardens, 1990, by Grant and Grant) about climbing Hydrangea (Hydrangea anomala ssp. petiolaris) and they all said this vine is wonderful and robust but very slow to establish. You may just have to wait a few more years.

This hydrangea prefers a cool, moist root run so be sure to irrigate it in the summer and place a good mulch (such as compost or wood chips) a few inches deep. The mulch should not touch the trunk of the vine at the top of the soil around the vine. Established trees and shrubs don’t generally need feeding. Avoid using a fertilizer that is high in nitrogen, or it may add lush, green growth at the expense of flowers.

Here is additional information, from Virginia Cooperative Extension:
Excerpts:
“Climbing hydrangeas only bloom on vertical stems so vines growing on
the ground will not bloom. Minimal pruning is required. They bear lacecap inflorescences with an outer ring
of showy white sterile florets around creamy to yellow fertile flowers in late spring. Deadheading can be
done right after flowering to save energy and for aesthetics by cutting the inflorescences off above the first
leaf. Branches that extend out far from the climbing surface may also be pruned back in summer after
flowering to prevent the plants from being pulled from their structures by heavy winds, ice or snow.”
Reasons for lack of flowers on various species of Hydrangea:

Improper shearing and renewal pruning on H. macrophylla and serrata cultivars
Frost injury to early expanding growth buds
Pruning more than a month after bloom time in summer
Excessive shade
Excess nitrogen fertilization

Magnolia grandiflora and failure to flower

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.

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. 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.

lack of flowers in star jasmine vines

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?

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).