Updated: Nov 18
When is the best time to prune your perennials in North Texas? Good question. Knowing how and when to prune your perennials has a big impact on how they will look as they grow, and even on their overall health. In this article and the accompanying video, you'll learn how to trim them back to keep your garden looking great.
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Perennial Pruning Basics
Many of us assume the best time to prune perennials is in the fall. But our North Texas climate can make timing your pruning chores a bit tricky. It also matters whether a perennial flowers on old wood or new wood. In this article, you'll learn why not all perennials can be pruned at the same time and when to prune yours. You'll also learn how to shape them to achieve the look you want.
We all want to prune in fall because, after a long, hot summer, our perennials start looking really ugly. But dormancy is a very important time for all plants. It's when they begin to store up energy for the next growing cycle. That energy is stored in the plants' roots. If you prune too early or too late you will disrupt this important phase of growth.
Make Sure The Plant Is Fully Dormant
Many Texas native perennials continue to bloom, or bloom again, in September and October and don't go dormant until we have a frost or freeze while some perennials only bloom on old growth. Plants in this second category need to be prune at a different time than your other perennials.
Pruning Old Growth Perennials
A good rule of thumb to follow is: don't prune perennials that bloom in early spring until (January-March).
Let's look at some specific cases:
Gregg's Mistflower is a Texas native perennial that does not go completely dormant until late winter or very early spring, so it should not be pruned until January or February.
Forsythia is another good example. If you look closely at the stems of a Forsythia, you will notice little buds forming all along the stem. Those buds will become flowers. Cutting them off will prevent the plant from blooming. It will bloom for about six to seven weeks and then it is done. At that time (roughly sometime in late April or May). you can then cut it back. It will re-grow all summer long and in the fall it will start setting buds again.
Irises are another one that look ugly after they've bloomed, but those ugly tops contain the energy the bulb will need for next year. If you cut the tops off too early, they will, most likely, not bloom the following year. It's better to let them go dormant naturally and wait until the tops are completely brown and lying flat on their own. You can reduce their unsightliness by braiding their leaves while they are still on the plant, which will encourage them to lie flat.
Examples of other plants that flower on old growth are: Indian Hawthorn, Euonymus, Barberry, Cotoneaster, Camellias, and Azaleas.
New Wood Bloomers
The other category of perennials are those that flower on new wood. Included in this group are Abelias, Crape Myrtles, Roses, Rose of Sharon, Panicle Hydrangeas, and Butterfly Bushes. For these plants, pruning stimulates new growth and they can be shaped or deadheaded anytime. The new growth will always come at the ends of the newly-cut stems. Most gardeners prefer to cut them back close to the base in winter to eliminate as much old growth as possible.
Pruning Perennials: Texas Timing
Here in the Dallas-Fort Worth area, we often do not experience winter weather cold enough to send our gardens into full dormancy. However, for your plants to look their best, you'll still want to prune at the appropriate time.
Bulbs, for example, have a limit on how much energy they can store, so removing the old growth in January or February is still desirable even if they haven't been fully dormant.
What's Special About Valentine's Day?
February 14 is not only a day to give your lover a romantic gift. It's also the day North Texans prune their roses. Other perennials can also be cut back at this time. Why? Because by this date we can usually be sure that our perennials our at their most dormant, so even in mild winters, it is considered optimum to do your pruning then.
The Right Way to Make a Pruning Cut
Knowing where and how to cut has a big impact on the look of your plants. When pruning perennials, it's always best to cut just above a new bud at a 45 degree angle. Be aware that the resulting cut will grow in the direction it points. That is, if you angle the cut outward from the center of the plant, it will to cause the plant to be wider, more open, and more airy. If you want the plant to be more dense and compact, you may want to encourage some of the branches to cross or grow more straight upward.
Never make a flat cut, as they will allow moisture to sit on the stem and encourage fungal growth or rotting that can lead to diseases.
Many newer varieties of Azaleas on the market are rebloomers, which means it will bloom profusely in early spring. You'll then want to "dead-head" or shear off the spent blooms to remove the dead plant material. They will re-bloom once or twice more during the growing season, although not as heavily as that first flush in the spring. Once it has completely finished reblooming, you can prune the plant back more heavily, down to about one foot in height.
Some Texas natives occupy a middle category somewhere between evergreen and perennial. In our climate they rarely die back to the ground. Instead their top growth just fades. Examples of perennials in this group are Artemsia and Lavender. Pruning these "in-between" plants in January or February will allow them to replace their old growth with new, prettier foliage.
A Word About Salvias
Texans love salvias (sages) for their variety and hardiness. They come in a huge range of sizes, growth habits and colors from the rounded, bushy Autumn Sage to the upright growing Victoria Blue sage to the low and leafy Culinary Sages.
Prune garden sages back to about six inches in February along with your roses and other new-growth perennials. This will keep them more compact and prevent them from becoming "leggy" later in the season.
Then, in mid summer, when the plant is looking it's worst, give it a "hair cut" by removing about six inches from the tops. This will stimulate new growth and cause it to bloom again. You can usually do this twice: once in early July and then again in mid to late August. However, be careful not to do this during winter when there is a danger of freezing weather as the cold will damage the new growth coming out.
Remember 'Sleep, Creep, & Leap'
Keep in mind that all plants, except annuals, take several years to reach their mature size. Perennials generally reach full maturity only in their third year. The first and second years it is working to establish the roots it will need when it is mature.
A good rhyme to help you remember is: "
The first year it sleeps, the second year it creeps, the third year it leaps."
Make sure all your plants are spaced according to their mature size. Don't crowd them just to fill up the space available.
Guidelines, Not Rules
This article and accompanying video provide general guidelines for how and when to prune most perennials, however, nothing substitutes for familiarizing yourself with the specific plants in your garden and their individual needs.
Ask The Experts
We're always here to help! If you have questions about pruning your the plants in your garden, give us a call or stop by the store and talk to one of our organic gardening specialists!