How to care for hydrangeas during spring? - Plant Care Guide

To care for hydrangeas during spring, focus on awakening them from dormancy with proper watering, fertilization, and timely pruning, all while protecting tender new growth from late frosts. Spring is a critical period that sets the stage for abundant summer blooms, so proactive attention to their needs is essential for a spectacular display. Understanding your specific hydrangea type is key, as pruning needs vary.

What Do Hydrangeas Need After Winter Dormancy?

After their winter dormancy, hydrangeas awaken in spring with renewed vigor, preparing for a season of lush foliage and abundant blooms. Providing the right care during this critical period ensures a healthy and vibrant display. The key is to support their emergence and new growth, while protecting them from lingering cold.

Here's what hydrangeas need after winter dormancy:

1. Water (Especially if Dry Winter/Spring):
   • Consistent Moisture: While dormant, hydrangeas don't need much water, but as soon as the weather warms and new growth begins to emerge in spring, they will start demanding moisture.
   • Check Soil: Even if there's been winter precipitation, check the soil to ensure it hasn't dried out. If your region experienced a dry winter or early spring, or if the hydrangeas are newly planted, give them a good, deep watering.
   • Why: Water is essential for new root activity and the expansion of leaves and flower buds.
2. Proper Pruning (Timing is Crucial and Type-Dependent):
   • Old Wood vs. New Wood: This is the most important distinction. Hydrangeas bloom on either "old wood" (last year's growth) or "new wood" (current season's growth). Pruning at the wrong time can remove flower buds.
   • When to Prune (General Spring Guidance):
     • Early Spring (After Last Frost): This is the window for pruning some types.
     • Remove Dead/Damaged Wood: Regardless of type, always prune out any clearly dead, diseased, or broken branches immediately after new growth appears (making it easy to identify dead wood). Cut back to healthy, green tissue. Use clean, sharp pruning shears or loppers.
     • Specifics (see next section for detail):
       • Bigleaf (macrophylla) & Oakleaf (quercifolia) Hydrangeas: Bloom on old wood. Only prune dead wood or crossing branches in early spring. Major shaping/hard pruning is done after flowering in summer.
       • Panicle (paniculata) & Smooth (arborescens) Hydrangeas: Bloom on new wood. Can be pruned more aggressively in early spring (before new growth becomes too vigorous) to shape and encourage stronger stems.
   • Why: Pruning redirects energy, promotes better airflow, and ensures a more attractive and productive bush.
3. Fertilization (After New Growth Emerges):
   • Timing: Wait until new growth has started in spring. Do not fertilize too early in dormant plants.
   • Balanced Approach: Use a balanced flower fertilizer or a slow-release granular fertilizer specifically formulated for flowering shrubs. Over-fertilizing, especially with too much nitrogen, can lead to lush foliage at the expense of blooms.
   • Color Adjustment (for Bigleaf Hydrangeas): If you want to change the color of Bigleaf Hydrangeas (pink to blue or blue to pink), spring is the time to apply soil amendments to adjust pH.
   • Why: Provides essential nutrients for the burst of spring growth and subsequent flowering.
4. Mulch (If Not Already Present):
   • Benefits: A 2-4 inch layer of organic garden mulch (e.g., shredded bark, pine needles, compost) helps conserve soil moisture, regulate soil temperature, and suppress weeds.
   • Application: Apply in early spring once soil has begun to warm, ensuring it's a few inches away from the base of the stems.
   • Why: Protects shallow roots from spring temperature fluctuations and helps maintain the consistent moisture hydrangeas love.
5. Protection from Late Frosts:
   • Vulnerable New Growth: Tender new leaves and flower buds that emerge in early spring are highly susceptible to damage from unexpected late frosts.
   • Protection: If a late frost is predicted, cover smaller bushes with a frost blanket, burlap, or an old sheet. Remove the covering once temperatures rise.
   • Why: Prevents potential damage to flower buds, ensuring future blooms.

By addressing these needs, you lay a strong foundation for your hydrangeas to produce their spectacular blooms throughout the summer.

How Do I Prune Hydrangeas in Spring Based on Type?

Pruning hydrangeas in spring is a crucial task, but the how and when depend entirely on the specific type of hydrangea you are growing. Pruning at the wrong time can result in no blooms for the season. The key distinction lies in whether they bloom on "old wood" (last year's growth) or "new wood" (current season's growth).

Here's how to prune hydrangeas in spring based on type:

Type 1: Hydrangeas that Bloom on "Old Wood"

• Examples:
  • Bigleaf Hydrangea (Hydrangea macrophylla): This includes Mophead and Lacecap varieties (most traditional blue or pink hydrangeas).
  • Oakleaf Hydrangea (Hydrangea quercifolia): Known for its lobed leaves, conical white flowers, and fall color.
  • Mountain Hydrangea (Hydrangea serrata): Similar to Bigleaf but typically smaller and hardier.
• Why They are Different: Flower buds for the current year's bloom are formed on the previous year's stems (old wood) in late summer or fall. If you prune these stems in spring, you are cutting off all the flower buds, resulting in no blooms for the season.
• Spring Pruning (Very Minimal):
  • When: Early spring, just as new growth begins to emerge from the base.
  • What to Remove:
    1. Dead Wood: Carefully identify and prune out any clearly dead, broken, or diseased branches. Look for stems that are brittle, hollow, or show no sign of green new growth. Cut these back to the ground or to a healthy main stem. Use clean, sharp pruning shears or loppers.
    2. Weak/Crossing Stems: Remove any very thin, spindly stems at the base that are unlikely to produce strong blooms, or branches that are crossing and rubbing against each other.
    3. Winter-Damaged Tips: If stems suffered winter dieback, prune back to the first set of healthy, green buds.
  • What NOT to Remove: Do NOT prune healthy stems that produced flowers last year, or any new green shoots coming directly from those old stems, as these contain your flower buds.
• Major Pruning: If significant size reduction or rejuvenation pruning is needed for these types, it should be done immediately after flowering in summer.

Type 2: Hydrangeas that Bloom on "New Wood"

• Examples:
  • Panicle Hydrangea (Hydrangea paniculata): Includes popular varieties like 'Limelight', 'Vanilla Strawberry', 'Quick Fire'. They often have conical flower heads and are very hardy.
  • Smooth Hydrangea (Hydrangea arborescens): Includes 'Annabelle', 'Incrediball'. Known for their large, often white, snowball-like blooms.
  • Some Reblooming Bigleaf Hydrangeas: Newer H. macrophylla cultivars that bloom on both old and new wood (e.g., 'Endless Summer', 'BloomStruck'). While they bloom on both, aggressive spring pruning will reduce old-wood blooms but they will still produce flowers on new wood.
• Why They are Different: These hydrangeas form their flower buds on the new growth that emerges in the current spring. This makes them very forgiving of spring pruning.
• Spring Pruning (More Aggressive Allowed):
  • When: Late winter to early spring, before significant new growth has occurred (or just as buds swell).
  • What to Remove:
    1. Dead/Damaged Wood: As with old-wood bloomers, remove any dead, diseased, or broken stems completely.
    2. Shape and Size: You can prune back stems aggressively to shape the plant, control its size, and encourage stronger stems that will support larger blooms.
       • You can cut back stems by 1/2 to 2/3 their length, or down to 1-2 feet from the ground.
       • Cut to a strong outward-facing bud.
    3. Thinning: Remove any very weak, spindly, or crossing stems to improve air circulation and direct energy to strong, productive growth.
  • Why: This type of pruning promotes robust new stems, which are where the flowers will form, leading to a more vigorous plant and better blooms.

Key Tool: Always use sharp, clean pruning shears for small cuts and loppers for thicker branches to ensure clean cuts that heal quickly.

By understanding your hydrangea type and applying these specific spring pruning guidelines, you ensure a spectacular bloom display and maintain healthy, vibrant shrubs.

How Do I Fertilize Hydrangeas in Spring?

Fertilizing hydrangeas in spring provides them with the essential nutrients they need to fuel robust new growth and develop their characteristic abundant blooms. However, the timing and type of fertilizer are crucial to avoid over-fertilization or promoting lush foliage at the expense of flowers.

Here's how to effectively fertilize hydrangeas in spring:

1. Timing is Key (Wait for New Growth):

   • Do NOT fertilize while the hydrangea is completely dormant.
   • When: The ideal time to apply fertilizer is in early spring, just as new growth begins to emerge from the woody stems and the ground. This ensures the plant is actively growing and ready to absorb the nutrients.
   • Why: Fertilizing too early (when dormant) can lead to nutrient leaching, root burn, or can unnecessarily feed weeds.

2. Choose the Right Fertilizer Type:

   • Balanced or Bloom-Boosting: Most hydrangeas benefit from a balanced, slow-release granular fertilizer (e.g., 10-10-10, 15-15-15) or a formula slightly higher in phosphorus (the middle number in the N-P-K ratio, e.g., 5-10-5 or 10-20-10) to encourage flower production.
   • Organic Options: Organic flower fertilizers (like bone meal, blood meal, or compost) are excellent slow-release choices.
   • Avoid Excessive Nitrogen: Too much nitrogen (the first number) can promote lush, leafy growth at the expense of flower production.
   • Specific for Bigleaf Color Change: If you are trying to change the color of your Bigleaf Hydrangea (H. macrophylla):
     • For Blue Flowers: Use a fertilizer with a high aluminum content and amend the soil with soil acidifier for hydrangeas (e.g., aluminum sulfate or elemental sulfur) to lower the pH (make it more acidic, 5.0-5.5). This allows the plant to absorb aluminum, which turns the flowers blue.
     • For Pink Flowers: Use a fertilizer with low or no aluminum and apply garden lime to raise the pH (make it more alkaline, 6.0-7.0).
     • Note: White hydrangeas are not affected by pH. Pink Bigleaf hydrangeas are the best candidates for turning blue.

3. Application Method:

   • Granular Fertilizers: Sprinkle the recommended amount of granular fertilizer evenly around the base of the plant, extending out to the drip line (the outer edge of the branches).
   • Work In and Water: Gently scratch the fertilizer into the top inch or two of soil, then water thoroughly. This helps the nutrients dissolve and penetrate the root zone and prevents root burn.
   • Liquid Fertilizers: Dilute liquid fertilizers according to package directions and apply as a soil drench.

4. How Much to Apply (Follow Directions!):

   • READ THE LABEL: Always follow the specific application rates and instructions on your chosen fertilizer product. Over-fertilizing can lead to nutrient burn, damaged roots, or excessive leafy growth with few flowers.

5. Mulch After Fertilizing (If Not Already Present):

   • After fertilizing and watering, apply or refresh a 2-4 inch layer of organic garden mulch around the base of the plant, keeping it a few inches away from the stems.
   • Why: Mulch helps conserve moisture and provides a slow release of additional nutrients as it breaks down.

By correctly fertilizing your hydrangeas in spring, you provide them with the optimal nutritional boost to develop strong stems, lush foliage, and the abundant, vibrant blooms they are famous for.

How Do I Protect Hydrangeas from Late Spring Frosts?

Protecting hydrangeas from late spring frosts is vital, especially for varieties that bloom on old wood (like Bigleaf and Oakleaf hydrangeas), as tender new growth and developing flower buds are highly susceptible to cold damage. A surprise late frost can completely wipe out your summer bloom potential.

Here's how to effectively protect hydrangeas from late spring frosts:

1. Monitor the Forecast (Your Best Tool):

   • Vigilance: Begin closely monitoring your local weather forecast as spring progresses, especially from mid-spring up until your average last frost date. Pay attention to warnings for "frost advisories" or "freeze warnings."
   • Temperature Threshold: Take action if temperatures are predicted to drop below 32°F (0°C), or even 35°F (2°C) if the new growth is particularly tender or there's a strong wind.

2. Cover the Bushes (Most Common Method):

   • Materials: Use lightweight materials that can trap heat but still allow some air circulation. Good options include:
     • Burlap: A natural, breathable fabric. Look for burlap rolls for plants.
     • Frost Blankets/Row Covers: Designed specifically for plant protection, these are lightweight, breathable fabrics. A plant frost blanket will provide insulation.
     • Old Sheets or Blankets: Avoid heavy, wet blankets that can become too heavy and dense.
     • Cardboard Boxes: Can be placed over smaller, newly planted hydrangeas.
   • How to Cover:
     1. Avoid Direct Contact: Drape the chosen material loosely over the entire bush, ensuring it doesn't compress the new leaves or flower buds too much. If possible, use stakes, tomato cages, or an existing frame to create a tent-like structure, keeping the material off the foliage.
     2. Anchor Securely: Secure the edges of the covering to the ground with rocks, bricks, or soil to trap warmth radiated from the earth.
     3. Remove Promptly: Remove the covering the following morning once temperatures rise above freezing, so the plant can get light and airflow. Leaving it on too long can cause overheating or fungal issues.

3. Water Thoroughly Before the Frost:

   • Why: Moist soil retains heat better than dry soil. Water releases latent heat as it freezes, which can help warm the air directly around the plant. Well-hydrated plant cells are also more resilient to cold.
   • How: Give your hydrangeas a good, deep watering a few hours before the predicted frost.

4. Bring Potted Hydrangeas Indoors:

   • Most Reliable: If your hydrangeas are in pots, the easiest and most reliable method is to simply move them into a sheltered, unheated garage, shed, or covered porch for the night.
   • Why: Provides complete protection from freezing temperatures. Remember to move them back out during the day if temperatures rise significantly.

5. Utilize Natural Shelter:

   • If some of your hydrangeas are planted near a warm building foundation, a fence, or under the canopy of a large evergreen tree, they may receive some natural protection, but still monitor and cover if temperatures are critical.

6. Avoid Premature Pruning in Spring:

   • For Bigleaf and Oakleaf hydrangeas that bloom on old wood, avoid major pruning in early spring before all frost danger has passed. The older stems and any existing dead foliage can actually provide a layer of insulation for new buds. Only prune clearly dead wood.

By diligently monitoring the forecast and taking these preventative actions, you can successfully protect your hydrangeas from late spring frosts, safeguarding their tender new growth and ensuring a beautiful season of blooms.