The best time to plant trees, flowers, or any plant is during the dormant season. In North America, this is usually late fall through early spring. While it's okay to plant during the rest of the year, it will require more maintenance from you in the form of watering, fertilizers, etc.
Summer isn't as ideal of a time to plant as spring or early fall, but with a few precautions, most plants will do fine. Peak sunlight and searing heat are added stressors on young plants with small roots, not to mention, summer soil tends to be drier.
The books are right – planting in the summer when it is hot and dry is not the best time to move new plants into or around the garden. During a particularly bad heat wave it can be hard enough to keep the soil hydrated, let alone provide ample moisture for plants that are establishing new roots.
Avoid moving plants in summer if at all possible. Being hoicked from the ground during hot, dry weather is stressful on plants and they'll respond by wilting or shedding leaves.
The rule of thumb has always been to plant in spring and fall when the weather is cooler. But a rising temperature doesn't mean you can't continue to fill the empty spaces in your garden with plants. Sure, there are some things you shouldn't plant in summer, such as a bare-root, newly dug or newly divided plant.
July is also a good time to plant fast-growing herbs like cilantro, basil, parsley, oregano, rosemary, chives, dill, sage and thyme. Start them from seeds or buy young plants. If you want to bring them indoors to overwinter, pot them up in containers and keep them in a bright window.
Most plants grow best in temperatures ranging from 59°–86°F. When temperatures above 90°F are sustained for long periods, plant growth is slowed, and some plants begin to show signs of stress.
So, how hot IS too hot for plants? The general answer is around 90 degrees F, with some exceptions to the rule.
Container-grown plants (like the ones you see at your local garden center) are the best option for summer planting. It's not the time to do bare root or transplant newly dug plants. However, container-grown plants can be planted without disrupting the roots. If you buy a plant in summer, don't save it to plant in fall.
Early spring and fall care are best times for transplanting. Then the weather is cooler and the plants are not using as much water. “However, don't move or transplant perennials while they are in bloom,” he says. “As a general rule, wait a few weeks after they bloom before moving.
In the desert southwest, including parts of Texas and California, you should wait until the average daytime temperature drops under 90F before you plant. The issue isn't only the air temperature, but the temperature of the ground.
You should take a break from feeding your plants during a heat wave or drought. However, to prepare them for conditions that could cause heat stress, regularly give them Miracle-Gro® Water Soluble All Purpose Plant Food (following all label directions) so they're nice and strong before the unfortunate weather arrives.
If extreme heat continues for weeks at a time, plants can actually die from a depletion of their food reserves. High temperatures can also cause severe water loss (desiccation) when transpiration (the process by which leaves release water vapor to the atmosphere) exceeds moisture absorption by the roots.
July is a great time to add quick-blooming wildflowers like Alyssum, Red Poppy, Zinnia, and Cosmos to your garden.
Your plants should be watered everyday, especially during the summer. They should also be watered in the morning. Morning is the best time to water because it gives the plants' leaves all day to dry out. This prevents fungus spots, which come from water sitting on leaves.
June and July are also good times to start seeds for perennials and biennials to bloom next spring. I sow seeds in a protected seed bed and then transplant seedlings in fall to overwinter, then bloom, ensuring me a wonderful spring greeting in the garden next year.
Ideally, the time to move most perennials is either spring or early fall. The hot, generally dry weather of summer is about the worst time of year to move any plant.
If you're seeing temps over 90 degrees Fahrenheit, consider covering your garden with shade cloth or planting your seedlings where they'll get afternoon shade from taller plants to help them out a bit. So there you have it: July is not the time to stop planting. In fact, it is the perfect time to keep planting.
Best time of day to transplant is early in the morning, late in the afternoon or on a cloudy day. This will allow the plants to settle in out of direct sunlight. The first step when transplanting daylilies from one spot to another is watering your plant well.
What's the Trouble with Hot Soil? When the temperature gets too hot, it's not just uncomfortable for you, but it can be harmful to your plants too. High temperatures can cause plants to lose too much water through transpiration, leading to wilting and even death in severe cases.
Move pots to cooler locations.
Place containers where they receive some shade during the hottest part of the day. This usually won't reduce their performance, but it will cool the plants and reduce water needs. Moving containers off or away from hot pavement will also help.
It can take anywhere from a couple of days to a couple of months for stressed plants to recover. Recovery time depends on the amount of damage that the heat caused to the plant. If a stressed plant is completely neglected during a heatwave, it can take several months or even be impossible to revive it.
Adding a layer of mulch around ground covers, shrubs, and trees will keep the soil a couple of degrees cooler while stopping it from drying out. Apply your mulch about three inches thick around the plants, spreading it near the drip line or water source. Ensure to keep it about six inches away from tree trunks.
In times of extreme heat, 1-2 times each week may be necessary. Know your plants though! Some plants prefer almost zero water during summer (manzanita, Ceanothus, madrone and cistus) and others wilt even when they have ample water (hydrangea, rhododendron). So adjust watering accordingly.