Fall is the perfect time to plant perennials. Texas gardeners should follow this roadmap

When it comes to perennials, the old Rule of Green Thumb is that “If it blooms in the spring, you transplant it in the fall, and if it blooms in the fall, you transplant it in the spring.”

Most of our popular perennials bloom in spring and early summer, so that means that the prime time to dig and divide them will be coming up in the next 4 to 6 weeks — September and early October. Several of the plant societies (Iris, Daylily, etc.) will be holding their annual sales, and friends and neighbors will be thinning out and replanting their own home gardens. This is the best time of the year to get your new beds of perennials planted and growing. Nurseries will even have some of your favorite fall bloomers in stock, so they can get mixed into the plantings at the same time.

Start with a plan

Any journey begins with a roadmap. Nowhere in your landscape is that any more important than with your perennial garden. Here are some things I’ve picked up by observing and maintaining perennial gardens for the past several decades.

▪ A plan drawn to scale on graph paper might help you keep track of the plants you have planted and when they bloom, also their sizes and colors so that you can keep your perennial garden filled with a nice sequence of color.

▪ Perennials show best if they’re in beds that are backed by evergreen shrubs. That way the bed doesn’t look barren for five winter months when everything is dormant. It’s usually best not to plant masses of perennials against the front of your house.

▪ Have enough depth to your perennial garden that you can plant several “layers” of color. That probably means 5 or 6 feet at a minimum. That will allow you to have taller, bolder plants in the background and more compact types in the front.

▪ It’s best to have a blend of 10 to 20 types of perennials so that something can always be blooming. That’s as opposed to a bed filled entirely with, for example, iris, daylilies or mums. Most perennials only bloom for two or three weeks. The rest of the year they are less than showy.

▪ Have a color scheme for your perennial garden. You may want to feature cheerful spring colors such as yellows, pinks and light blues March through May. By June consider cooling shades of lavender, purple, pale yellow, blues and others. Plan on rich fall colors of golds, oranges, reds and burgundy in September and up until frost.

▪ Prepare your perennials’ garden soil well before you start planting. Work 5 or 6 inches of organic matter into the top foot of soil. That would include equal amounts of sphagnum peat moss, well-rotted manure, well-decayed compost and finely ground pine bark mulch. Combine 1 inch of expanded shale and use a rear-tine rototiller to blend it all together to a very fine consistency. All of this will ensure a raised bed that will drain well during periods of heavy rains.

▪ Include a few small evergreen shrubs such as dwarf hollies or low junipers in the bed to give it interest during the “off season.”

▪ Use tall perennials to the back of the plantings and low, spreading plants in the front. That seems too obvious, but it’s amazing how often we end up with oversized plants obscuring our views of the beauties behind them.

▪ Plant your perennials in clusters and groupings rather than in long, straight rows. The plantings will look more natural, plus those smaller “pockets” will come into bloom, then fade from sight more gracefully than if they make up big masses that run the length of the landscape.

▪ Dig and divide your perennials when they begin to become crowded. For most types that’s going to be after three or four years. Some types will need attention more frequently. I think of Shasta daisies — I end up dividing them every couple of years. Other perennials may never need to be bothered. Spider lilies, oxblood lilies and other heirloom bulbs fit into that camp.

▪ Mulch your perennial beds with shredded tree leaves from your lawn each fall to keep the garden tidy and weed-free. As plants finish a bloom cycle, deadhead their old flower stalks with pruning shears, removing yellowed or browned foliage at the same time.

Which perennials are best?

If ever there were an arbitrary list, this is it. These are perennials I’ve found to be outstanding for flowers or foliage for Texas.

For sun, plant hardy amaryllis (St. Joseph’s lily), Powis Castle artemisia, cannas, chrysanthemums, daylilies, fall asters, gloriosa daisies, hardy hibiscus (mallows), iris, Bath garden pinks, purple coneflowers, purpleheart, rock rose, several species of salvias, Shasta daisies, thrift and yarrow.

For shade, choose from Texas Gold columbine, autumn fern, holly fern, southern wood fern, four o’clocks, hellebores, leopard plant, oxalis, oxblood lilies, spider lilies, summer phlox, summer snowflake, sweet violets and lamb’s ear.

You can hear Neil Sperry on KLIF 570 AM on Saturday afternoons 1-3 p.m. and on WBAP 820 AM Sunday mornings 8-10 a.m. Join him at www.neilsperry.com and follow him on Facebook.

This story was originally published September 2, 2022 at 5:30 AM.