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The Best Time to Plant Perennials

Caren White is a Master Gardener and instructor at Home Gardeners School. She has been associated with Rutgers Gardens for over a decade.

A newly planted perennial garden at Rutgers Gardens

A newly planted perennial garden at Rutgers Gardens

Perennials can be planted any time during the growing season. In fact, you can plant them right up until the ground freezes. For the best results, though, you should plant them in either the spring or the fall.

How to Plant Perennials in the Spring

By far the best time to plant perennials is in the spring. Your local nursery will have a large selection of perennials to choose from. You can plant hardy perennials in the early spring when the ground is no longer frozen. The warming soil will encourage the plants to establish roots and begin foliage growth. Your plants will be well established when the heat of summer descends on your garden.

When planting your perennials, remember that they will get much bigger than they are in their containers, so be sure to allow enough space for them to grow in your garden. Water your plants well, then dig holes that are larger than the root balls. Remove the containers, place the plants in the holes and fill in the soil around them taking care that the top of the root ball is level with the top of your planting hole. Water the plants again to moisten the surrounding soil and then add a layer of mulch to prevent your plants from drying out too quickly and to discourage the growth of weeds which compete with your garden plants for water and nutrients. Be sure to water your newly planted perennials regularly to help them get over transplant shock and establish themselves in their new homes.

How to Plant Perennials in the Fall

My favorite time to plant perennials is in the fall. I’m digging holes in the garden for bulbs anyways. I may as well pop a few perennials in as well. The soil is still warm enough for them to establish their root system before going dormant in the winter. When spring rolls around, they will have a head start on spring planted perennials. As the air and soil warms, your fall planted perennials will be sending up new foliage while your spring planted perennials will still be trying to establish their root system.

Plant them the same as you would in the spring. Mulch is even more critical in the fall than in the spring. Mulch will even out the soil temperature during the winter to prevent frost heave. Frost heave occurs when the soil alternately freezes and thaws. Plants can be literally thrust out of the ground. It’s a good idea during the winter to make regular trips to your garden to check on your plants. If any have been pushed up, simply step on the surrounding soil (not the plants) to push it back down.

Fall blooming perennials such as asters and chrysanthemums are usually planted in the spring rather than the fall. If you plant them in fall, they will not bloom until the following year.

How to Divide Perennials

Fall is the best time to divide your perennials. Perennials need to be divided every 3 to 5 years. As the clumps get larger every year, the middle tends to die out. Not only is this unsightly, it is also unhealthy for the plants. The dead portions invite insect and disease infestations that can kill the healthy parts of your plants.

To divide your perennials, dig them up and pull all of the healthy part of the plant off of the dead portion. Discard the dead material and replant the healthy plant. You can further divide the healthy plant into smaller plants to either increase the number of plants in your garden or to trade with another gardener for plants that you desire.

Your local nursery will still have a few perennials for sale in the fall. The variety will be much smaller than in the spring, but they will be heavily marked down. Plants will not survive the winter in containers so retailers need to get rid of them. Take advantage of these sales to fill your garden with perennials. Even if the plants look terrible, as long as they have some foliage, after being planted they will send out new roots until the ground freezes and dormancy sets in. In the spring, your “ugly” plants will send out new growth and look no different from your other perennials.

How to Plant Perennials in the Summer

Heat is the enemy of newly planted perennials, so planting them during the summer is not recommended. If you must plant or transplant during the heat of the summer, there are a couple of steps you can take to maximize their chances to survive.

Choose a cloudy day or wait until the late afternoon or early evening when the sun is not as hot. Then water, water, water! Water your new plants every day for at least two weeks to reduce heat stress as they settle into their new home. Planting early in the morning is not recommended. The heat of the afternoon is too stressful for newly planted plants.

I like to wait until rain is in the forecast. If it is due late in the day, I take advantage of the clouds to get my planting done before the rain starts. If the rain is due in the morning, I plant the evening before. A good soaking rain is always better for any plant than watering by hand as you would when planting. Then I observe the same “water every day for two weeks” rule after the rain.

Perennials provide your garden with years of reliable color. Give them a good start by planting them in the spring or the fall.

Questions & Answers

Question: We are doing a front yard landscape this weekend in June. Can you give me some perennials for full sun?

Answer: That's a tough question! You haven't told me where you live. This is important for a number of reasons. Most importantly, plants that are hardy in one area of the country are not hardy in other areas of the country. A perfect example are salvias. I love salvias, but I have to grow almost all of them as annuals in my zone 6 NJ garden because they are not hardy here. In southern parts of the country all types of salvias are hardy and grown as perennials.

How much sun does your garden get each day? "Full sun" is defined as a MINIMUM of 6 to 8 hours of sun each day. If your garden only gets sun in the morning or in the afternoon, that is considered partial shade. Plants requiring full sun will be stunted in partial shade and most of them will refuse to bloom.

What is your climate like? Is it arid like the southwest? In that case, you will need to plant drought tolerant plants. Is it wet like the Pacific Northwest? Then you will need plants that can tolerate lots of moisture.

What kind of soil do you have? Most plants will not grow in clay or sandy soils but I can't tell you how to amend your soil if I don't know what kind you have.

How large is your garden? Smaller gardens are best planted with smaller plants while large gardens can handle large plants.

Your best bet is to visit your local nursery. They will know which plants are perennial in your area and what kind of soil you have and how to correctly amend it.

After you install your plants in your garden, make sure that you water, water, water. Summer is the worst time to be planting perennials. They should be planted in the spring or the fall when it is cooler and less stressful for the plants.

© 2013 Caren White

Comments

Caren White (author) on April 08, 2019:

Vanita, it depends on what growing zone you live in. A good rule of thumb to follow is whether or not your soil is frozen. If it is not frozen, then you can plant your perennials outdoors now. If it is still frozen, then you will need to wait until later in the season when it has thawed out.

Vanitakindredholmes on April 07, 2019:

When 2 plant prenials i live in gary indiana and they are blooming in the house on my kitchen table

Caren White (author) on January 16, 2014:

thanks, Janais! glad you enjoyed it.

Janais on January 15, 2014:

Too many comtpimenls too little space, thanks!