Growing Concerns 575: Hydrangea flops, ground covers, pinching pointers

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Now that's what we're talking about -- how to make sure now that there will be LOTS of buds on your mums and a great fall show! 

Early Summer: Hydrangea, drought tolerant ground cover, pinching pointers, thumbs up- and down to butterfly weed and stump dissolvers

Help for a hydrangea that's fallen and can't get up!


The pride of my garden is Hydrangea 'Annabelle' It's 5' wide and 5' tall, with blooms bigger than a dinner plate. I cut it back hard every year. I love it - until it rains.

The flower heads get so heavy with rain they flop to the ground and don't bring themselves up again. Worse, when I try to stake around them, they flop over the stakes and the stems break. I even tried propping umbrellas overhead when we're expecting hard rain, but that's not very pretty and more work than I want. I'm out of ideas. Anyone have a solution? - F.K.

Dear F.K.,

Thanks for a new idea -- one that with bright golf umbrellas could create a very pretty scene!

Try this: Thin it in the spring after you cut it back -- nip off 2/3 of the canes that sprout. Scratch in bone meal this fall. The stems should thicken after thinning, when each one has more light, less competition for nutrients, plus phosphorus from bone meal.

Bone meal or "one cup of super phosphate (0-0-20) per wheelbarrow load of soil," as contributor Hunter Sr. was taught many years ago. He still follows that practice and feels it gives his tomatoes denser, sturdier stems, keeps their height down, and makes all the difference with new roses, too.

To hedge your bets, right after you cut back the hydrangea, lop some three- or four foot long sturdy branches from a yew, burning bush or other shrub you usually shear. Pick limbs with forked outer tips but straight, strong wood below. (Photos and more how-to in Stakes from sticks.)

Don't worry, those other shrubs can spare the wood. Cut them by April 1 and you won't notice by June. The bushes will fill in that fast from side shoots off nearby limbs formerly too dark and crowded to grow.

Push those branches securely into the ground all around the hydrangea, making a circle just an inch wider than the hydrangea itself. Put them in so the forked ends are up and 30 or 40 inches above ground.

If this looks a little silly when you first do it, stand back a pace and you'll see it's as if there's a shrub there not yet leafed out. The hydrangea will come up right through the props so you won't notice them in just a few weeks. Yet the hydrangea will take note!  As it blooms it will lean into and over those crutches.


In search of ground cover for a dry area

I have a very large area that needs a drought tolerant ground cover. The area goes up and down my driveway on both sides. That's full sun, and must be able to handle being walked on. I'd like to have something lemon/lime color, chartreuse I believe is the right name for it, so it will be lighter than the grass. -F -

Dear F.,

The key words in your question are 'must be able to handle being walked on.' There are groundcovers that fit all the other requirements but only one, grass, can handle constant footwear.

How about making a wide-spaced stepping stone path in that area, then plant ground covers such as stonecrop (Sedum kamschaticum or S. acre), golden thyme (a Thymus variety) or yellow lamium LamiumAureumN8245s.jpg (L. maculatum 'Aureum', a plant we usually place in shade, but take a look at our notes about it in  our notes about it in Choosing shady plants for why we're changing our minds). Gro575ThymeSedumN7980s.jpg

Right: Two sedums (blue arrows) and a thyme (orange arrow) mix it up in a rock garden. We do walk in this bed to reach the yews and perennials beyond. That can squash some plants' stems but their roots are safe between and under the rocks, so they regenerate, just as lawn grass does after a good stomping.

Those plants will eventually grow right over the stones yet they will still be there to take the impact when anyone walks in the bed. You should consider "quilting" different groundcovers so you won't have a monoculture that a disease, bad year or insect can wipe out all at once.

You should look into permeable paving, too, using a product such as Grasspave2. Permeable paving products were developed for areas that must be planted yet carry some traffic, such as in botanical gardens where many people walk or emergency vehicles need access.

Imagine plastic netting into which are bonded slices of PVC pipe, like two-inch deep, open-bottom cups. You cut the sections of fabric to the size and shape you need and lay them on the area, which you've excavated and lined with coarse sand. Dig that area deep enough that the top of the PVC cups sits at ground level, then fill over the whole thing with soil and plant it. The plastic takes the weight, the plants provide the cover.

Ask at local landscape supply companies for this product. We've found such firms more than willing to order it in -- even before they learned we were going to write about it here.


Predecessors left us with pinching pointers

My aunt used to say "On midsummer's day, pinch your flowers away." Maybe because it was a rhyme and I heard it often as a child, it's stuck with me, but I've never figured what all she meant by it. Do you know? - P.A. -


Midsummer -- summer solstice -- may not top your list of holidays but its influence on your garden should make it a red letter day.

June 21 is the longest day of the year. More important, from many a plant's perspective, it's when nights begin to lengthen. Ancient, calendar-less people who watched the skies closely to decide when to plant, fertilize and harvest noticed an end to the gradual increase in day length and subtle northward shift of the rising sun. Since the sun seemed to stand still in the sky that day, the solstice was named from the Latin for "sun" and "still."

The ancients celebrated the day as a beginning and an end. Plants mark the day, too. Mums, asters, and some other late blooming plants will react soon after the solstice to lengthening nights by changing their internal chemistry. Altered hormone levels at the tip of each branch will cause flower buds to form.

Your aunt knew that if she wanted to lengthen the season by delaying flower formation on these plants, there was work to do -- solstice couldn't be a stand still day for that gardener!

Rather than dancing and celebrating with other sun-watchers, she probably went out and made that last pinch on the late bloomers while the plants were still "in the mood" to make new branches.

It doesn't matter whether you use scissors, hedge shears, or a weed whip, just clip stems back at the end of June or very early in July to reduce each plant's height by 1/3. Two or more new branches will form at each cut end, making the whole plant bushier and multiplying the number of tips that will flower.

Removing existing branch tips also delays the onset of bud formation. It resets the already-ticking hormone-driven meter in each branch end, shifting the plant's peak bloom to a later date.

For certain species, long nights may be the most significant factor in flower bud formation. These short day plants -- more accurately called long night plants -- need uninterrupted darkness for a set number of hours during each 24 hour period. Without this, flower-production hormones don't reach the required levels. Bathe such plants for even fifteen minutes in the glow of anything brighter than the moon and the hormone production cycle may be broken. That year's flower production may suffer or fail.

Mums that sit quietly in fall while other mums shout with color and asters that are disasters on the floral scene may be suffering from the horticultural equivalent of sleep deprivation. So for the best fall show, pinch and then move those fall blooming plants away from your porch lights or street lighting.

What happened to these mums, that bloomed only in patches two months later than others elsewhere in the garden? Check Long nights  for the whole story.



Green thumbs up

to the brilliant orange and red-orange of butterfly weed (Asclepias tuberosa) in its isolated-clump splendor in the fields. (Please don't dig or pick - you can buy one!)


Green thumbs down

to products that promise to "dissolve stumps." Nothing but time and moisture dissolves a stump. Spend your money on an ax.

Originally published 7/17/04