Design a Sequence of Blooms for Color All Season Long

My garden surprised me this spring as it bloomed in a riot of colors just after most of the Primulas had finished flowering in April. It was absolutely delightful as stems of flowers from 10 inches tall to nearly 4 feet tall bloomed in pinks, whites, blues, cherry reds, maroon and yellow with a smattering of bicolored blooms showing up in unexpected colors and places.

I suspect that hummingbirds may have been the cause and provided the results as they traveled from bloom-to-bloom last year, inadvertently taking pollen from one colored bloom to another nearby, resulting in what we call open-pollinated hybrid crosses. The result was this year’s riotous show of early color from late April into late June. All this in a garden that for years has had its peak color and blooming period from July into August, not in the spring.

I couldn’t have planned it better as Mother Nature did her handiwork.

This whole new period of blooms and color in my garden got me thinking about the subject of sequence of bloom. This is the art of being able to blend plants in the garden whose bloom colors, heights, sizes and most importantly time of bloom keep the garden in color for months and months instead of short stints of blooming interspersed with periods lacking in color. And yes, more proof to my feeling that you can have a perennial garden that blooms for months on end without the use of annuals. But how do you plan a sequence of bloom and what tools are at our fingertips to use?

First off, garden centers are not necessarily our friends in this adventure. Yes, in many cases they are the main supply source of the plants we’ll use as well as our mail-order sources. However, there is an issue with seeing a plant in bloom at a garden center and then integrating it into the garden. In most cases when you see a plant blooming in a garden center or nursery and it’s growing in a container like a 1-gallon pot, you are most likely seeing a plant blooming out of its normal bloom cycle.

This happens because most of the plants we buy are blooming several weeks to a month earlier than they will bloom in our gardens. This results from the plants being overwintered in structures that are essentially greenhouse-type cold frames, which keep plants cool in winter then warm up early in the season.

For this reason, your sequence of bloom design needs to rely on natural blooming cycles and not induced blooming cycles. But there’s also another element at play — year and again, we must look to Mother Nature. I can drive just a few miles away and the plants blooming there won’t bloom for as long as another two weeks in my neighborhood. Even on my small property there are microclimates that result in identical plants on one side of the property blooming days to a week later or earlier than the identical plant just 100 feet away. Soil temperature and light exposure are in play here as well.

I never ever said this was easy. But when it works, when you finally have everything in harmony, it’s quite remarkable and incredibly rewarding replete with grins, smiles and pure, unadulterated wows.

If you didn’t catch on sooner to what caused my earlier-than-usual color this year, it’s the columbines, the Aquilegias. They are great seed producers and seem to have been cross-pollinated en masse by last year’s hummingbird swarm. The seeds drop from the columbines in July and since they are light germinators the seeds germinate on top of the soil in the summer and many, if not most bloom the following spring as they did this year.

Knowing this, some gardeners go through the garden in early spring and “weed out” most of the seedlings or thin them to just a few. Less experienced gardeners see the seedlings and mistake them for Oxalis (clover) seedlings and they get weeded. Being able to tell the difference is critical in having enough columbine seedlings to survive and fill in.

But now the columbines are quickly fading, and as they do the other garden plants that provide my main season of color and blooms are filling in and sequencing quite well. I could tell you I planned all this. The truth though is that there has only been rudimentary planning for the sequence of bloom based on years of observations. The rest, not quite by accident but more by happenstance.

In one section of the garden, I had structural issues with several varieties of tall perennial geraniums. As they got taller, some up to 2 feet and 3 feet tall with their blue, chocolate and pink flowers, there was nothing to hold them up and prevent them from toppling in the wind or quick but powerful rain showers. This year they are all upright and brilliant as the stem and branch structure of the fading columbines support the geranium stems keeping them upright and their flowers blooming in thin air rather than faltering on the ground or needing unsightly staking. Geranium “Johnson’s Blue” stands 40 inches tall instead of matting on the ground, all thanks to the columbines.

In another area I have a strain of Dianthus barbatus, or sweet William, that I collected seed of a plant I’d found at an abandoned house years ago. This species of Dianthus can get a bit sloppy, but I love the deep rich crimson color of the flowers so I’ve collected seed from the plant and always have a few for replacements.

Ah, but how to keep this plant upright and not looking sloppy? Again, the remaining columbine stems are keeping the Dianthus upright, but as the columbines fade away and in spite of my best efforts, the Dianthus will need some support in the weeks to come.

In several other places, another self-seeding perennial/biennial has been growing its velvet crowns and foliage. Columbines are interspersed, and as they fade the stems of the self-seeded Digitalis (foxglove) have emerged. Now where there was a mass of our native Aquilegia canadensis, there are tall spikes of Digitalis ambigua, and others have 2-foot flower spikes and are close to being in full bloom. Another great succession of bloom.

Up at the opposite end of the garden where there’s more sun, I have three types of Allium planted, and they’ve bloomed from late May up to now. But the earliest of the tall, blue-headed Alliums have now faded, and the last of these large globe flowers is just peaking. These Alliums range in height from 2 feet to just over 3 feet, and what would fill in and sequence well while still giving me a purple to blue color with some height?

Enter the Thalictrums. One of the shorter Thalictrums, “Nimbus,” is on the short side and has a lighter blue color true to its name. It came into bloom about midseason of the Alliums and three weeks later is supplemented then replaced by the taller and darker colored T. aquilegiifolium as the last of the Alliums lose their color. But the show isn’t over then. “Nimbus” is followed by the taller and blue(er) Thalictrum “Black Stockings.”

The last of my Thalictrums is the species rochebruneanum, which often towers over the garden with its purple/blue flowers later in the summer. It’s quite tall, with the plants often ranging from 6 to 8 feet. The feathery foliage remains intact through the summer, but the tall blue flowers draw the eye upward into a garden spot that has some of my tallest plants including several varieties of Asiatic lilies that will bloom from late July into August in a succession of bloom that keeps the garden fresh, colorful and ever changing.

There’s also a yellow Thalictrum flavum glaucum that is just flowering now. It’s not as full and robust as the others, but the yellow is an interesting color among the blues.

Visit gardens as they open for public view, but view with a critical eye for some of these gardens are not totally true to sequence as the owners buy in and supplement some of the gardens with recently purchased plants just to add color and fill-ins.

Beware that many plants have their own sequence of bloom within the group. Peonies are a good example as you can find early-, mid- and late-blooming plants that will extend the season for as much as a month to six weeks. But you need to be careful in the type of peony that you choose because you also need to be aware of their height at bloom — not just the time of bloom.

Asiatic and Orienpet lilies are also a great group of plants to work with for season of bloom as some (usually short ones) begin to bloom in June while I have one or two that don’t bloom until late July and well into August. The later ones tend to be taller (up to 8 feet tall in bloom) and when using these wonderful bulbs you have to consider more than their exquisite flowers, but their scent as well. The stronger-scented varieties should probably be planted away from porches and windows, and the incredible scents can result in your nose running faster than you can catch it. Also read up on the scarlet lily beetle before you establish a collection of lilies.

And yes, you can certainly work in other plants into your sequence of bloom. Trees, shrubs and ornamental grasses can be integrated into the garden, but here your skill set will be tested for a number of reasons. The results can be quite interesting as these features can add critical structural elements as well as multiseason appeal.

There’s an old Cornell booklet on sequence of bloom of perennials, biennials and bulbs that’s been out of print for ages but you can find a copy online here: tinyurl.com/2utvt4zu. This is a long-term project if you want it to work well, and it can be ongoing for years and years. As all gardens and gardeners should. Keep growing

If you have Phlox subulata in your garden now is the time to trim it. Cutting it back 2 to 4 inches will result in a lusher plant next spring with more dense flowering. The cutting can be rooted in damp sand.

Watch out for Japanese beetles as they are emerging. I don’t expect a large outbreak this year though as the larvae or white grubs need moist soil to survive in. If you haven’t noticed, moist soil is in short supply.

Don’t let your Geranium phaeum “Raven” go to seed or it’ll come up all over your garden next year. Use sheers to remove the blooms en masse.

Two-spotted spider mites love hot and dry weather. They can do great damage to a wide range of ornamentals. In the garden I find them most troubling on Phlox paniculata, or the tall garden phlox. They’re hard to spot, and by the time you note their damage (spotting and stippling of the leaves) the populations have gotten very high. Easy enough to manage these nearly microscopic eight-leggers. (True insects, which mites are not, only have six legs. They wash off easily with sprays of water and I’ve had very good success with neem oil. However, oils like neem should not be used when it’s over 85 degrees and sunny. When they show up, spray every four to seven days, making sure you hit the underside of the leaves where they feed.

Last chance to disbud your chrysanthemums if you want shorter plants with more blooms. Just roll the buds off with a finger by July Fourth. This causes blooming to be delayed by two weeks, but on much nicer looking, compact plants.