You couldn’t resist that perennial on sale at the garden center, so you brought it home. But, you’re concerned about planting it in the heat of summer. Keeping your new perennial alive in its plastic pot probably poses more of a challenge than digging it into the ground. Planting in summer is possible, you just need to take a little more care than you would in the spring and fall when conditions are more favorable. I’m going to share some tips that should help set a new plant up for success, even if it’s planted in July or August.
In my garden, I do all my main planting—containers, perennial beds, vegetable garden—through the spring and early summer. However depending on plants I might accidentally on purpose bring home, I also plant in the summer and fall in my USDA zone 6a garden in Southern Ontario. Annuals, of course, are not as much of an issue, since they only last for the one season. But when you spend your hard-earned money on a perennial, you expect it to come back.
One benefit of planting in the summer months is it allows you to better identify the empty spaces that need to be filled in a garden. Most of your plants are likely in full bloom by this point, or they have leafed out and reached their full size, like a hosta. This makes it easier than the spring to figure out spacing.
Browsing perennials for planting in summer
One of the best chances at success when planting in summer is to purchase plants that have hardy characteristics, like drought and heat tolerance, salt tolerance, etc. In my garden, these include coreopsis, catmint, lavender, and sedum. Native plants will have adapted to the environmental conditions of your region. My favorites include and various varieties of aster.
If you plant a small seedling in super-hot weather, you may go out the next day to find a withered up little stem. Go for the bigger pots where there will be a larger root mass. If you’re shopping in the summer, chances are you’ll be choosing from well-sized pots.
Read plant tags carefully for height and spacing considerations and, of course, to determine whether your plant needs full sun, full shade, or anything in between. What you might want to consider is planting a full sun plant in more of a shady location until the weather cools down a bit towards fall.
Just as shade cloth can be used to protect certain vegetables or newly planted seeds from a hot summer day, it can be used to provide part shade conditions to a new perennial, too.
Try to avoid planting in the midst of a drought
One caution is that you may want to avoid planting perennials in a period of drought. Even plants that are drought-resistant need regular water to become established. Some communities may have water bans during certain times throughout the summer. It’s best to respect these requests and not plant anything during these periods.
Plants that don’t like being planted in the summer include bare root plants or freshly dug out plants. It’s best to avoid transplanting and dividing perennials in the summer heat as it can affect the roots, which are crucial for directing water and nutrients to the plant.
Time your planting
Don’t wait until the heat of the day is cooking the established garden bed. When planting in summer, try to time it so you’re planting early in the morning or in the early evening. You may also want to wait for a cloudy day.
Prepare your perennial
Give your new perennial a thorough watering before you plant, thoroughly soaking the root ball. When you remove the plant from the pot, gently loosen the roots a bit before setting it into the hole, especially if the plant is very root bound in the pot.
Prep your garden for planting in summer
If you notice after the first good rainstorm (or anytime) that the root ball is inching above the soil, you may want to dig your plant in a little deeper. The root ball should be level with the soil line, but roots should be covered. This helps prevent the root ball from drying out.
Mulch the garden
A layer of mulch over a garden area helps the soil below to conserve water and keeps the area around the plant cool. I use a shredded cedar mulch in my front yard garden. It also helps keep the weeds down, which can compete with new plants for space, water, and nutrients.
Watering a perennial planted in summer
New plants need more water to become established. Water deeply about three times a week. If it rains, you’re off the hook! Check regularly for signs your plant is in distress. That may indicate you need to water more (or maybe even less).
Fertilizing a newly planted perennial
The main issue when caring for a new plant, especially one planted in mid to late summer, is that you want the roots to become established. But you don’t need lots of new growth on the top of the plant.
Look for transplant fertilizer to add to your new perennial or shrub at the time of planting, or a fertilizer with low nitrogen and higher phosphorus. I’ve used a product called Root Rescue that I got at a garden show. It features mycorrhizal which seek out extra water and nutrients in the soil that the roots aren’t able to find on their own.
Whichever product you choose, make sure it’s right for your garden conditions, and apply it according to the package directions at the time of planting. Ask the experts at your local garden center or nursery if you are unsure. After planting, don’t worry about fertilizing again during this first growing season. Wait until the following spring.
Keep a close eye on your plant
You’ll want to really pay attention to your new plant, especially throughout that first week, to ensure it’s adapting well to its new environment. Sometimes, despite our best intentions and care, plants fail to thrive in their new location, no matter when you are able to plant them. If you keep your receipt, some nurseries will provide a refund up to a year after you purchase the plant.