Regular walks through the garden reveal evolving spectacles of diverse botanical cycles. There’s always something new to observe and learn from.

We are now approaching the end of the spring season (June 21, to be exact) and the beginning of the summer season.

Several plants have already blossomed and faded in my garden. I’ve enjoyed this year’s swath of daffodils (Narcissus ‘Mon Cherie’) that decorates the beds along my front sidewalk, the bright yellows blossoms of the prize-winning hybrid iris, ‘That’s All Folks,’ and fragrant white, lavender, and rose lilacs (Syringa vulgaris ‘Angel White,’ ‘California Rose’ and ‘Lavender Lady’).

These are all well past their seasonal displays. The daffodils’ leaves have gone limp, and will soon be ready for trimming. They have been in the ground for just one season, so they need not be lifted for another three years.

The irises also can be cut to the ground and the rhizomes left to produce new life next spring.

The dried brown lilac blossoms are being dead-headed for appearance and to promote new growth. Also, one-third of the larger branches will be cut to the ground to control overall growth and to open the inner plant to sunlight and air.

Other plants on their way out include the Corsican Hellebore (H. argutifolius) and the hybrid tea roses (several varieties). These plants are still providing great color in the garden. The roses should be dead-headed and the hellebores’ flower stalks will need to be cut to the ground to make space for new growth.

This quick survey of plants past their best time of the year does not include the complete plant inventory but represents the seasonal changes.

The late spring and early summer plants are taking center stage. The accompanying photos are random selections of plants currently in bloom.

The garden includes several succulent plants that do change seasonally, but mostly grow larger. They do flower for propagation, but we enjoy them year-round for their fascinating foliage forms.

This season is the right time for the annual Chelsea Chop. We’re still within the appropriate period for this timely practice, which is named for the Royal Horticultural Society’s Chelsea Flower Show, in late May.

The objective is to cut back summer and autumn-flowering perennial plants by one-third to control their size and promote additional flowering. Larger more straggly plants could be cut back by one-half.

This practice involves the removal of the top shoots, which inhibit the side shoots through a process called apical dominance. Pinching out or pruning the apical bud allows the lower buds to sprout, creating bushier, branched growth.

Here are some of the plants suitable for the Chelsea Chop: Achillea, Anthemis tinctoria (golden marguerite), Artemisia, Aster, Campanula, Cranesbill (hardy geranium), Echinacea (coneflower), Eupatorium (Joe Pye weed), Helenium, Helianthus (perennial types), Iberis (candytuft), Monarda, Nepeta (catmint), Penstemon, Phlox paniculata (garden phlox), Rudbeckia (black-eyed Susan), Sedum (upright forms), Solidago (goldenrod) and Veronicastrum.

Some mounding plants that bloom in the summer can be refreshed by shearing off the old foliage to stimulate new leaves and another round of flowers. Candidates for this treatment include Cranesbill, Nepeta, Achillea, Lamium, Aquilegia, Threadleaf Coreopsis, Alchemilla, Epimedium, Pulmonaria, and Brunnera.

If you haven’t Chelsea chopped your plants in previous years, and hesitate to whack away at your plants, use this year to gain experience. Select likely candidates in your garden, and prune back some of them to observe the effects.

Recall the pleasures of spring, and enjoy the arrival of the summer season!

Advance your knowledge

Botanical research at UC Santa Cruz is contributing to Earth’s preparation for challenging events in the future. Researcher Emily Sessa is pursuing research designed to understand how plants recovered after the mass extinction event 66 million years ago.

With support from NASA, the UC Santa Cruz research team collected fossilized prehistoric plant life, simulated the post-apocalyptic environment in a campus laboratory, and planted dozens of plants that represented plant life in the late Cretaceous period. After six months, they evolved the simulated environment to resemble the Earth’s historic transformation and monitored the plants’ adjustment.

They observed the impressive resilience of the Deer Fern (Blechnum spicant), which grows today in many areas, including on California’s coast. The research continues to understand the source of that resilience.

Paleobotanist Scott Wing, from the Smithsonian Institution, commenting on this mass extinction event, was quoted saying, “If you want to understand the effects of global devastation on ecosystems and evolution, this is the first chapter in Earth history to turn to. It is also a great chapter for trying to understand how life recovers over both ecological and evolutionary time.”

For more of this story, visit latimes.com/science.

Mark your garden calendar

The Ruth Bancroft Garden will present the webinar “Basic Irrigation in Dry Gardens,” at 10 a.m. on June 21. “An irrigation system appropriate for a dry garden is critical for long-term success with your water-wise plant palette. Learn how to assess your landscape and install a drip irrigation system that is suitable for dry gardens.” Register for this fee-based event by visiting ruthbancroftgarden.org and scroll down to “Featured Events.” That website also provides info on future webinars.

Tom Karwin can be reached at gardening@karwin.com