Everything Hydrangeas - The Ultimate Guide to Growing, Planting, and Caring

The Ultimate Guide to Growing Hydrangeas

Hydrangeas are quite popular and widely appreciated for their large, colorful blooms and versatility in garden design. Did you know more than 70 species of hydrangeas exist in the world? In some cultures, hydrangeas hold significant meanings and are used in various celebrations and rituals, further boosting their popularity. This month, our garden experts at Copper Creek dig deeper into this beloved perennial and share what you should know to help your hydrangeas grow, including identifying plant zones, planting, watering, fertilizers and amendments, and pruning.

Colors of Hydrangeas

Hydrangeas are like a blooming chameleon. An interesting fact about hydrangeas is that the color of their flowers can change based on the pH level of the soil in which they are planted. In acidic soils (with a pH of less than 5.5), hydrangea flowers tend to be blue; while in alkaline soils (with a pH above 7), the flowers are more likely to be pink. This unique characteristic is due to the availability of aluminum ions in the soil, which are more soluble in acidic conditions and can be absorbed by the plant, leading to blue flowers.

Pinky Winky™ Hydrangea Tree

Varieties of Hydrangeas

Not all varieties are created to flourish here in Minnesota. The United States Department of Agriculture has determined plant zones to help gardeners identify the best plants for their area based on climate variations. The Plant Hardiness Zone Map was most recently updated in 2023 and resulted in revisions of many plant zones in Minnesota, notably the south and central parts of the state. To learn more about Plant Hardiness Zones, check out our article here.

Berry White® Hydrangea

Hydrangea Varieties Suitable for Central Minnesota

Taking into account this important data, Copper Creek’s Garden Center in Nisswa carries more than a dozen different varieties of hydrangeas suitable for central Minnesota. They include:

• Berry White® Hydrangea

• Bobo® Hydrangea

• Fire Light™ Hydrangea

• Fire Light Tidbit™ Hydrangea

• Incrediball® Hydrangea

• Invincibelle Ruby Hydrangea

• Invincibelle Wee White® Hydrangea

• Little Hottie™ Hydrangea

• Little Lime™ Hydrangea

• Little Quick Fire® Hydrangea

• Annabelle Hydrangea

• Diamond Rouge® Hydrangea

• Incrediball® Hydrangea

• Invincibelle Hydrangea

• Limelight Hydrangea

• Little Lime Punch Hydrangea

• Pinky Winky™ Hydrangea

• Pop Star Hydrangea

• Quick Fire® and Quickfire Fab™ Hydrangea

• Strawberry Sundae® Hydrangea

Limelight Hydrangea Tree

Specialty Hydrangea Trees

There are also a few unique, specialty hybrid trees – hydrangeas grown into mini tree form – that are very fun and popular in the area, including:

• Berry White® Hydrangea Tree

• Firelight Tidbit™ Hydrangea Tree

• Limelight Hydrangea Tree

• Little Lime™ Hydrangea Tree

• Pinky Winky™ Hydrangea Tree

Our gardening professionals at Copper Creek typically recommend the Bobo® Hydrangea (smaller and hardy), the Berry White Hydrangea (very pretty), and the Quick Fire® Hydrangea (large with big blooms, and typically deer hardy) to local customers.

Annabell Hydrangea

Planting Hydrangeas

It’s time to get your hands dirty and start planting your hydrangeas. But, before you start to dig, carefully look at the tag on your plant and determine if it will thrive in the location you’ve selected.

Considerations for Planting

A few things to take into consideration:

• Does this plant require full shade or full sun?

• What soil type is desirable?

• How tall and wide will the plant become?

• How often should the plant be watered?

• When will it bloom?

• Other characteristics desired by the planter and/or crucial to the perennial’s success.

When to Plant Hydrangeas

Hydrangeas have a long blooming season, often from spring to late autumn, providing extended periods of visual interest in gardens. In Minnesota, the best time to plant hydrangeas is spring or early fall. These times provide moderate temperatures and allow the plants to establish their root systems before the extremes of summer heat or winter cold set in. Here are some guidelines:

• Spring: Planting in late April to early June allows hydrangeas to establish their roots during the mild spring weather. This timing helps the plants become well-established before the heat of summer.

• Fall: Early September to mid-October is another good time to plant hydrangeas. The cooler fall temperatures reduce transplant shock and allow the roots to grow before the ground freezes.

How to Plant Hydrangeas

We’ve covered the where and when, so let’s get to the ‘how.’ Planting hydrangeas is relatively straightforward and requires only a few basic gardening tools. Here's a list of tools you will need and are available at the Garden Center at Copper Creek:

• Shovel or spade for digging the planting hole.

• Garden trowel for more precise digging and adjustments around the plant.

• Compost or organic matter to amend the soil and improve fertility and drainage.

• Watering can or hose to water the plants thoroughly during and after planting.

• Pruners to trim any damaged roots or branches.

• Mulch to help retain moisture and regulate soil temperature.

• Gloves to protect your hands while working with soil and plants.

• Measuring tape to ensure proper spacing between plants (optional, but helpful).

Steps for Planting Hydrangeas

With the proper tools in hand, here are a few helpful steps putting your hydrangeas in the ground:

1. Choose a location – Select a spot with partial to full shade and well-draining soil.

2. Prepare the soil – Mix compost or organic matter into the soil to enhance its quality.

3. Dig the hole – Use a shovel or spade to dig a hole twice as wide and as deep as the root ball of the hydrangea.

4. Place the plant – Gently place the hydrangea in the hole, ensuring the top of the root ball is level with the surrounding soil.

5. Backfill the hole – Use the garden trowel to fill the hole with soil, pressing gently to eliminate air pockets.

6. Water thoroughly – Water the plant deeply to help it settle in and establish roots.

7. Mulch around the base – Apply a layer of mulch around the base of the plant to conserve moisture and suppress weeds.

Soak Your Hydrangea Before Planting

We are often asked if it’s necessary to soak the hydrangea roots before planting. The simple answer is, yes. Soaking ensures that the root ball is fully hydrated, which helps reduce transplant shock and supports the plant's initial growth. Well-hydrated roots are more pliable and can spread out more easily in the new soil. Moist roots can also more effectively absorb nutrients from the soil, promoting healthier growth.

To soak the plant:

• Submerge the root ball: Place the root ball of the hydrangea in a bucket or tub of water. Ensure the entire root ball is submerged.

• Time: Let the plant soak for about 15-30 minutes. This should be enough time for the roots to absorb plenty of water.

• Drain excess water: After soaking, let any excess water drain off before placing the plant in the ground.

Trimming the Roots on Your Hydrangea

Trimming the roots of a hydrangea before planting is not always necessary, but it can be beneficial in certain situations. Here are some guidelines on when and how to trim the roots.

How to know when it is time to trim the roots on your hydrangea:

• Root-bound plants – If the hydrangea is root-bound (roots are densely packed and circling the container), trimming can help encourage new growth.

• Damaged roots – If you notice any damaged, diseased, or dead roots, trimming them off can promote healthier growth.

• Promote root spread – Trimming can help stimulate the roots to spread out into the surrounding soil.

How to Trim Your Hydrangea Roots

1. Inspect the roots – Carefully remove the hydrangea from its container and inspect the root ball.

2. Loosen the roots – Gently tease the roots apart with your fingers. If they are very compacted or circling the pot, use a sharp, clean knife or pruners to make vertical cuts (about 1 inch deep) around the root ball.

3. Trim excess roots – If the roots are excessively long or damaged, use pruners to trim them back. Remove any circling or matted roots.

4. Soak the roots – As mentioned earlier, soak the root ball in water for 15-30 minutes.

Watering Your Hydrangeas

Watering hydrangeas properly is crucial for their health and flowering. Here are some tips on how to water hydrangeas effectively.

General Watering Guidelines

• Consistency: Hydrangeas prefer consistent moisture. Avoid letting the soil dry out completely between waterings.

• Depth: Water deeply to encourage the roots to grow deeper into the soil. Shallow watering can lead to weak root systems.

• Frequency: Generally, hydrangeas need about 1 inch of water per week, either from rainfall or supplemental watering. In hotter climates or during dry spells, they may need more frequent watering.

Specific Watering Tips

• Morning watering: Watering in the morning is ideal as it allows the plant to absorb moisture before the heat of the day. It also helps prevent fungal diseases by giving the leaves time to dry before evening.

• Soil moisture: Check the soil moisture regularly. Stick your finger into the soil about 1-2 inches deep. If it feels dry, it's time to water. If it's still moist, wait a day or two before checking again.

• Mulching: Mulch around the base of the hydrangea to help retain soil moisture and regulate temperature.

• Drip irrigation: Consider using drip irrigation or soaker hoses to deliver water directly to the roots, minimizing water waste and reducing the risk of fungal issues.

Fertilizers and Soil Amendments for Hydrangeas

Hydrangeas benefit from regular fertilization and soil amendments to support healthy growth and abundant blooms. Here are some guidelines for fertilizing and amending the soil for hydrangeas.

Fertilization Guidelines

• Timing: Fertilize hydrangeas in early spring as new growth begins and again in mid-summer. Avoid fertilizing late in the season, as it can encourage new growth that may not harden off before winter.

• Balanced fertilizer: Use a balanced, slow-release fertilizer with equal parts nitrogen (N), phosphorus (P), and potassium (K). A 10-10-10 or 14-14-14 formula works well.

• Avoid excessive nitrogen: Too much nitrogen can result in lush foliage at the expense of blooms. Follow the recommended application rates on the fertilizer package.

• Organic options: Organic fertilizers, such as compost, well-rotted manure, or fish emulsion, can also provide nutrients to hydrangeas.

Soil Amendments

• pH adjustment: As mentioned earlier, the soil pH can affect the color of hydrangea flowers. To lower pH (for blue flowers), add sulfur or aluminum sulfate. To raise pH (for pink flowers), add lime.

• Organic matter: Incorporate organic matter, such as compost or well-rotted manure, into the soil to improve fertility, drainage, and moisture retention.

• Mulching: Apply a layer of mulch around the base of the plant to help retain moisture, suppress weeds, and regulate soil temperature.

Pruning Hydrangeas

Pruning hydrangeas is essential for maintaining their shape, encouraging new growth, and maximizing flower production. Different types of hydrangeas require different pruning methods. Here are some general guidelines.

Pruning Guidelines by Type

• Mophead and lacecap hydrangeas (Hydrangea macrophylla): These types bloom on old wood (last year's growth). Prune them right after they finish flowering, usually in late summer. Remove spent flowers, deadwood, and weak stems. Avoid heavy pruning, as it can reduce next year's blooms.

• Panicle hydrangeas (Hydrangea paniculata): These types bloom on new wood (current year's growth). Prune them in late winter or early spring before new growth begins. Cut back the previous year's growth by about one-third to one-half, shaping the plant as desired.

• Smooth hydrangeas (Hydrangea arborescens): These types also bloom on new wood. Prune them in late winter or early spring. Cut back the stems to about 6-12 inches above the ground to encourage vigorous new growth and larger blooms.

• Oakleaf hydrangeas (Hydrangea quercifolia): These types bloom on old wood. Prune them after flowering, removing spent blooms and any dead or damaged wood. Avoid heavy pruning, as it can reduce next year's blooms.

General Pruning Tips

• Clean tools: Always use clean, sharp pruning tools to make clean cuts and reduce the risk of disease.

• Remove deadwood: Regularly remove dead, diseased, or damaged wood to improve the plant's overall health and appearance.

• Shape the plant: Prune to shape the plant and control its size. This helps maintain an attractive form and prevents overcrowding.

• Avoid late-season pruning: Avoid pruning hydrangeas in late summer or fall, as it can stimulate new growth that may not harden off before winter.

By following these expert tips from Copper Creek, you'll be well on your way to growing healthy, vibrant hydrangeas that will be the envy of your neighborhood. Happy gardening!