Late Season Plant Shopping

How to pick a plant

By John Murgel.

Summer is here and most gardeners are working on keeping things growing and happy in the heat. Still, you might find yourself needing one or two more plants for various reasons—a gap in a container, deaths in a garden bed, or perhaps the siren song of the “sale” plants at the garden center.

Whatever the reason, you can help ensure success of new plants late in the season with a few reasonable steps.  The first step should be taken before you leave the house--and is a good place to begin any time you’re considering adding plants to the garden.  Ask yourself, “What is my goal for this (as yet hypothetical) plant?” 

It’s all too easy to fill a cart with plants at the nursery. “I’ll figure out where to plant them later,” we say.  But having your objective in mind, along with a timeframe, will narrow your list of potential plants considerably. 

For example, suppose you want a plant for privacy screening on the back patio.  A new shrub could be just the ticket—except that if the patio needs to be screened ASAP, that shrub may not come through for you in time.  You’ll need a shorter term solution to go along with it, or in place of it. 

Perhaps a vigorous annual growing in a container, or even a containerized tree to be planted elsewhere in the landscape could be considered while your carefully selected, “permanent” shrub establishes itself. 

Step two is to describe the site. What growing conditions will the plant face?  The landscape goal combined with a careful analysis of growing conditions may lead you to a very short list of possibilities. 

Your garden’s growing conditions include the USDA zone of course, but more importantly, known insect or disease pressure in the area (Japanese Beetles come to mind), the size of the growing space, irrigation availability, microclimates (aka hyper-local weather extremes), drainage, soil texture and pH, and salt.

In the first two steps, we came up with possible plant species or varieties that would fit the bill.  In step three, we consider the plants themselves, as individuals.  If you’re looking for a rarity, you may well have to take what you can get.  If, however, you’re in the market for plants that are available from a few retailers, you’ll want to compare plant sizes, stem development/branching, the growing regime (container vs B&B, greenhouse vs field, etc), and the logistics of moving plants to the site.  It’s tempting to go with plants that are as large as possible, but research has consistently shown that smaller plants tend to establish more quickly—and they sure are easier to carry.  Remember that plants grown in a greenhouse or in other parts of the country will need to be acclimated to our dry air and intense sunlight.

Once you have a clear idea of your landscape goal along with its timeframe and your list of possible plants, it’s off to the plant store!  At this point in the season, some plants may have just arrived from a wholesale nursery, and others may have been patiently waiting on the benches for weeks.  Evaluate plant health—what do you see that is normal or not normal?  How are the neighbors looking?  Steer clear of plants that are obvious misfits from others of the same type.  Even if they’re on super-sale, they may not be worth your effort.  Some plants may have a medical history—look for symptoms like leaf spots and scorched margins.  If they’re distributed only on the older leaves, you may be in the clear; symptoms distributed across all the foliage or limited to new leaves are a red flag.  Be sure to check the plants from all angles. Plants may appear uniform from one vantage point, while another view could reveal health problems.

These plants were cut back and show healthy new growth.

Plants are maintained at the nursery, too.  Be sure to recognize the difference between a plant having been cut back to keep it manageable on the sale bench and a plant that has died back. (Hint: look for strong new growth from leaf axils). 

Remember, too, that seasonal plants like poppies and bleeding-hearts are going to look terrible in a container in July, but if planted soon could put on a lovely garden display next year.

Look at the plant habitat in the nursery. Is the potting mix covered in algae?  The plant may be being overwatered.

Check the roots by gently sliding the rootball out of the pot (yes, you’re allowed to do this).  Look for healthy, firm roots that are dense enough to hold the soil together. 

Finally, get your plants planted as quickly as possible.  It’s already late in the season and having them languish even longer in their nursery pots serves neither you nor them.  Because summer is extreme in temperature, proper planting is paramount.  Consider washing the roots of perennials to remove the bulk of the potting mix. This allows for quick contact with the garden soil and promotes establishment.  Your plants, even those that want “full sun,” will likely appreciate some shade for the first several days.  A wide range of shading materials are options, depending on your aesthetic tolerance.  Cut conifer branches remain classic and popular, as do custom sail-cloth shades, or even patio chairs. Just make sure that the sides of your shelter remain open so that airflow continues, and remember that you want to temper the light, not eliminate it. 

And don’t forget to water!

John Murgel is the Horticulture & Natural Resources Extension Specialist (aka Extension Agent) in Douglas County, CO. His interests include ornamental horticulture and drought-tolerant gardening.