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Are the ‘Dog Days’ of summer taking their toll on your flowers?

The midsummer malaise can hit plants as the heat rises. Learn how to help your plants thrive despite the heat.

Contributors: Rick Schoellhorn

 

If I was sitting in a room with no idea what month it was, I could probably come pretty close to guessing the month simply by the kind of questions we get from gardeners. By midsummer, gardeners start asking why the magic stopped in their containers and baskets - plants have stopped flowering and are just sitting. We try our best to diagnose each case as it comes along, but there are some common themes that crop up over and over. We thought a simple article detailing the common issues gardeners face in summer might help answer a few of your questions.

 

COMMON SUMMER ISSUES

What you often see in the heat of summer and moving into fall is a combination of issues: soil drying out, fertilizer running out, high temperatures exhausting the plants, and sometimes the accumulation of old flowers, or seed. Each of these things builds up over time and causes the plant stress.

For example, each time a plant dries out to the point of wilting, it hardens the plant a little bit, like hardening arteries in people. The stems get thinner, the water has a harder time getting through the thin stems and slowly the plant loses its ability to really power out new flowers and new growth. The same is true when the fertilizer runs out, or the temperatures are extremely high, or the plant starts to set seed… they all cause the plant to lose strength.

Here's how you can help your plants cope with the summer conditions:

  1. Try to make sure plants are always moist (not soggy but never wilting). For many folks, a drip irrigation system can do this and can be set up on a simple timer to water your plants each day. It is simple to install and simplifies your life. This is a tough thing to pull off, but is certainly a worthy goal.
  2. Try increasing your fertilizing frequency as we pass the midway point of summer. Give the plants a little extra food to help them deal with summer temperatures and conditions. A slow release fertilizer is good, but I think the instant energy of a water soluble is even better.
  3. Water your plants thoroughly. The potting soil by this time of year frequently begins to pull away from the sides of the pot, which is bad news because it means more of your water is running around the outside of the root ball instead of percolating down through it. Thoroughly hydrating the soil can mitigate this issue. Water your container, wait thirty minutes to give the soil time to soak up water, then water again. Repeat a few times. Alternately, put six or so inches of water in a tub, sit the container in the tub for a few hours and let it soak up water until the soil is rehydrated.
  4. Give your plants a haircut. If things become stressful for your plants, they may try to make seed. We don't want that to happen because those seeds divert a lot of energy away from new growth. Removing the spent flowers or seed heads (deadheading) with a sharp pair of scissors or clippers will help the plant use its energy to make new flowers and foliage. 

 

DEALING WITH HIGH TEMPERATURES  

If you live in a warm climate, late summer temperatures can reduce flowering, as most traditional summer annuals do not like temperatures above 90F during the day or night temperatures much above 60-65F. When temperatures get too high (especially high night temperatures) it makes it very hard for the plant to rest and build up strength and store any food. If the heat is making you really uncomfortable, many of your plants are likely uncomfortable too. So as each day begins, the plant is working off a food deficit from the day before.

The best thing you can do in this situation is choose to grow plants that are more heat tolerant, like Luscious® Lantana and Blue My Mind® Evolvulus. You'll find more suggestions for heat and drought tolerant plants here, plants for the south here, and for all climates here. Choosing plants that are well-adapted to your summer conditions is the best way to keep your garden beautiful all summer long.

 

CHOOSING A CONTAINER SIZE

In hot climates, it is very hard to keep plants happy in 8-10" hanging baskets. They are the torture chamber of the hot summer garden, a tiny pot hanging outside in the wind, being cooked all day by the sun, and not enough soil for the plants' roots to find a place to grow all season long.

Consider buying larger hanging baskets in spring or transplanting your smaller ones in to larger containers for summer. You should be able to find ones that are 14", 18", or even 20" in diameter. Larger pots with more soil volume won’t dry out so fast and generally grow better all season than plants in smaller pots. Make sure that whatever you hang them from is strong enough to hold the weight of it when it's wet. Nobody wants to pull hooks out of the soffit or have a large container go crashing to the ground. 

 

FEEDING YOUR PLANTS IS CRITICAL TO SUCCESS

Potting soil that contains fertilizer is a great for getting your plants off to a good start in spring, but the amount of fertilizer it contains is not enough to last all summer. We recommend feeding your plants with a water soluble plant food every third time you water your plants. If you've had a lot of rain, the fertilizer will get washed out of the container more quickly so you'll need to fertilize again. We also recommend that you add our continuous release plant food to the soil when you pot up your plants in spring. This type of fertilizer slowly releases food to your plants over a period of several months. We've formulated our plant foods to contain special micronutrients and iron which will keep your Proven Winners flowers blooming strong all season. If you store it in a tightly sealed container in a dry place like a storage shed or cabinet it will last indefinitely.

Plants are like people. Everything they have gone through during their short lives has shaped the way they will perform in the future. Few of us can provide the perfect environment for every plant all of the time but by making a few changes here and there, we can help our gardens continue to perform through the dog days of summer.

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Anonymous's picture
Anonymous Thu, 07/26/2018 - 10:40am

My Supertunia Bordeux's are dying. I water every other day, fertilize every 10 days. They are in "window box" type planters with coco liners. I have them planted with Supertunia Bubblegum, which is doing great. I don't know what to do. Help.

Anonymous's picture
Anonymous Thu, 08/24/2017 - 9:41am

My plant problem is that they grew TOO LARGE. I have coleus and petunias in three pots, petunias and verbena in another and just petunias in another. They are huge. I've pinched back the coleus all summer long but they are still enormous. And now the petunia stems are too long and are hanging down unattractively. I've been tempted to cut everything back but think it may be too late in the season for them to rejuvenate. Next year I won't fertilize as much I guess. Any ideas?

Kerry Meyer's picture
Kerry Meyer Wed, 10/04/2017 - 4:30pm

Trimming back earlier in the year would help keep the plants under control.  It is pretty late to cut them back at this time. Slowing down on fertilizer would also decrease the rate of growth, but you don't want to completely stop fertilizing.  You calso look for less vigorous plants in the spring as well.  Coleus come in wide range of sizes, so choosing something that doesn't get as big would make maintaning them much easier.  Lastly, you could always consider moving to larger planters, which will better accommodate the larger plants better and make keeping them well watered easier as well!

Anonymous's picture
Anonymous Mon, 08/14/2017 - 1:44pm

As if the heat of summer isn't enough, then come the Japanese beetles. They are still destroying marigolds I have planted in pots!

Sarah Geoghegan's picture
Sarah Geoghegan Tue, 08/15/2017 - 9:34am

You could try Neem Oil on your marigolds for those pesky beetles.
Hope this helps!
Sarah
Proven Winners

Anonymous's picture
Anonymous Fri, 08/11/2017 - 8:29am

Excellent article and reminder of the basics. Here in Indiana we can see all sorts of summer conditions. This summer started very wet, now is very dry. My plants have not thrived as they normally due, especially the ones in containers. I realize after reading this it's back to basics of appropriate watering and fertilization and perhaps different choices of plants for next season. Thank you!

Anonymous's picture
Anonymous Sat, 07/14/2018 - 7:18am

I too live in Indiana and totally ageee with all you said!
I am just returning from a week long Florida vacation! My husband was in charge of watering my lovelies! I hope I am not disappointed in their performance when I get home! I did fertilize them before leaving but, as you said, I have been disappointed in my flowers this year!!! Makes me want to invest strictly in perennials!

Anonymous's picture
Anonymous Sat, 08/12/2017 - 8:05am

Great article! We have flowers in pots, baskets & large containers around our clubhouse & by mid July they're looking really sad. This article will be very helpful next Summer when we do this all over again!

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