Is it okay to prune in summer?

Yes, it is generally okay to prune in summer, and for many plants, it's actually the ideal time for specific types of pruning. While dormant season pruning (late winter/early spring) is common, summer pruning serves different, but equally important, purposes for plant health, shape, and fruit production. It's crucial, however, to understand what to prune and how to prune during the warmer months to avoid stressing your plants.

What is Summer Pruning For?

Summer pruning is primarily focused on shaping, maintenance, and influencing fruiting, rather than heavy structural cuts. Unlike dormant pruning which removes larger limbs, summer pruning involves lighter cuts to manage growth. It helps direct the plant's energy more efficiently and can improve air circulation and light penetration within the canopy.

Why Prune in Summer?

Pruning in summer offers several unique benefits:

• Controlling Growth: It slows down vigorous growth, especially on fruit trees, by removing foliage that is actively photosynthesizing. This can be useful for maintaining plant size.
• Encouraging Fruit Production: For many fruit trees, summer pruning encourages the development of fruit buds for the following year and improves the size and quality of the current year's harvest.
• Improving Light and Air Circulation: Removing inner branches and dense foliage allows more sunlight to reach ripening fruit and lower leaves, and improves airflow, which can reduce disease.
• Maintaining Shape: It's easier to see the natural shape of a plant and make aesthetic adjustments when it's in full leaf.
• Removing Problematic Growth: You can quickly spot and remove dead, diseased, or damaged branches, as well as suckers and water sprouts.

What Plants Can You Prune in Summer?

Many types of plants benefit from summer pruning, including fruit trees, deciduous shrubs, evergreens, and even some flowering plants. The key is knowing the specific needs of each plant and understanding the type of pruning appropriate for summer. Not all plants are suited for heavy summer cuts.

Fruit Trees

Summer pruning is incredibly important for many fruit trees, especially apples and pears. It helps manage their size and encourages fruit bud formation.

• Apples and Pears: This is arguably the most important time for pruning these trees.
  • Purpose: To reduce vegetative growth, encourage spur development (where fruit forms), and improve light penetration to ripening fruit.
  • What to remove: Remove upright, vigorous "water sprouts" and suckers from the base or limbs. Thin out overcrowded branches, especially those shading fruit. Shorten long, whip-like growths to 4-6 leaves from their base to encourage fruit spurs.
  • Timing: Late July to early September, after the main flush of spring growth.
• Cherries, Plums, and Apricots (Stone Fruits): These are best pruned in summer to avoid fungal diseases.
  • Purpose: To reduce the risk of Silver Leaf disease (a fungus that enters through pruning wounds).
  • What to remove: Dead, diseased, or crossing branches. Lightly prune for shape and size.
  • Timing: Mid-summer, after fruiting, when the tree is actively growing and can quickly heal wounds.
• Citrus Trees:
  • Purpose: To shape, remove deadwood, and improve air circulation.
  • What to remove: Dead, crossing, or weak branches. You can lightly prune for shape.
  • Timing: After the last fruit harvest, but before the next bloom.

Deciduous Shrubs

Many deciduous shrubs, especially those that bloom on new wood (current season's growth), benefit from summer pruning after they've finished flowering.

• Summer-Flowering Shrubs: Examples include Hydrangeas (certain types like panicle and smooth hydrangeas), Rose of Sharon, Spiraea (some types), and Crape Myrtle.
  • Purpose: To encourage more blooms, remove spent flowers (deadheading), and maintain shape.
  • What to remove: Spent flower heads to encourage rebloom (deadheading). Lightly prune for shape. For reblooming hydrangeas, remove faded flowers to encourage new ones.
  • Timing: As soon as they finish flowering.
• Evergreens
  • Conifers: Most conifers (pines, spruces, firs, junipers) are best pruned in early summer after their new growth (candles) has expanded but before they harden off.
  • Purpose: To control size and maintain density.
  • What to remove: Trim new growth by 1/2 to 2/3. Avoid cutting into old wood on most conifers, as they often don't regrow from it.
  • Timing: Late spring to early summer.
  • Broadleaf Evergreens: Examples include Boxwoods, Holly, and Laurels.
  • Purpose: To shape, maintain size, and promote dense foliage.
  • What to remove: Lightly trim for shape or to remove errant branches.
  • Timing: After new growth has matured, usually early to mid-summer.

Flowering Perennials and Annuals

• Deadheading: Removing spent flowers is a form of summer pruning crucial for many flowering plants.
  • Purpose: To encourage continuous blooming by preventing the plant from putting energy into seed production.
  • What to remove: Just the faded flower head, or cut back to a set of healthy leaves.
  • Timing: Throughout the blooming season as flowers fade.
• Pinching: Removing the growing tip of a stem.
  • Purpose: To encourage bushier growth and more flowers (e.g., basil, petunias, coleus).
  • What to remove: The very top few leaves and growing tip.
  • Timing: Early in the season to encourage branching, or throughout for continuous harvest (herbs).

Hedges

• Purpose: To maintain a neat, tidy shape and promote dense growth.
• What to remove: Trim back new growth to maintain the desired height and width.
• Timing: Light pruning can be done multiple times throughout the summer as new growth emerges.

What Plants Should You NOT Prune Heavily in Summer?

While many plants tolerate or even benefit from summer pruning, there are some important exceptions and cautions. Avoid heavy structural pruning in summer for most plants, and be especially careful with spring-flowering shrubs.

Spring-Flowering Shrubs

These plants set their flower buds on old wood (growth from the previous year). Pruning them in summer (or even late spring) will remove those undeveloped flower buds, resulting in fewer or no blooms next year.

• Examples: Lilacs, Forsythia, Rhododendrons/Azaleas, Magnolias, Viburnums, Weigela.
• When to Prune Them: Prune these plants immediately after they finish flowering in spring. This gives them the rest of the growing season to develop new wood and set buds for the following year.
• Emergency Pruning: If you must remove a dead, diseased, or dangerous branch from a spring-flowering shrub in summer, it's okay, but understand you'll sacrifice next year's blooms on that part of the plant.

Evergreens (Heavy Pruning)

While light shaping is okay, heavy pruning of evergreens in summer should be avoided.

• Reason: Heavy cuts into old wood on many conifers can stress the plant and may not regrow. Broadleaf evergreens can suffer from sunscald on newly exposed inner branches if too much foliage is removed.
• When to Prune Heavily: Major structural pruning of evergreens is generally best done in late winter or early spring before new growth starts.

Trees with Sap Bleeders

Some trees are known to "bleed" excessively when pruned during active growth periods (spring and summer). While not usually harmful to the tree's health, it can be messy and disconcerting.

• Examples: Maples, Birches, Walnuts, Elms.
• When to Prune Them: These trees are best pruned in late fall or early winter after they've dropped their leaves and are fully dormant, or in mid-summer when sap flow has slowed down. Avoid early spring pruning for these.

Newly Planted Trees and Shrubs

• Reason: Newly planted specimens need all their energy to establish a strong root system. Pruning removes energy-producing leaves and adds stress.
• Exception: Only prune dead, broken, or crossing branches on new plants.

What are the Risks of Summer Pruning?

While beneficial for many plants, summer pruning isn't without its risks, especially if done incorrectly or in extreme conditions. Stress, sunburn, and increased vulnerability to pests or diseases are the main concerns. Understanding these risks helps you prune wisely.

Plant Stress

• Energy Depletion: When you remove leaves in summer, you're removing the plant's food factories (where photosynthesis occurs). Excessive removal can deplete the plant's energy reserves.
• Reduced Growth: This energy drain can slow down overall growth, which is sometimes the goal (e.g., for fruit trees), but can be detrimental to young or struggling plants.
• Recovery: The plant needs to expend energy to heal wounds and produce new growth, potentially stressing it further, especially in hot or dry conditions.

Sunburn (Sunscald)

• Newly Exposed Bark: When dense outer foliage is removed, the bark of inner branches or the trunk, previously shaded, can be suddenly exposed to intense summer sun.
• Damage: This can lead to sunscald, where the bark cracks, discolors, or even dies. This damage can be unsightly and create entry points for pests and diseases.
• Prevention: Avoid removing large amounts of outer canopy. If you must, consider providing temporary shade for severely exposed areas, especially in hot climates.

Pest and Disease Vulnerability

• Open Wounds: Pruning creates open wounds, which are direct entry points for fungal spores, bacteria, and insects.
• Active Period: Summer is often when many fungal diseases and insect pests are most active.
• Prevention:
  • Clean Tools: Always use clean, sharp pruning tools to make clean cuts that heal quickly. Disinfect tools with rubbing alcohol or a bleach solution between plants, especially if you suspect disease.
  • Prune During Dry Weather: Avoid pruning on rainy or very humid days, as moisture encourages fungal growth.
  • Specific Plant Needs: Pruning stone fruits (cherries, plums) in summer is specifically to avoid diseases like Silver Leaf, which are more active in dormant seasons.

Reduced Frost Hardiness

• Late Summer/Early Fall Pruning: Pruning too late in the summer or early fall can stimulate new, tender growth.
• Winter Damage: This new growth may not have enough time to harden off before the first frost, making it very susceptible to cold damage.
• Prevention: Stop all significant pruning several weeks to a month before your average first frost date. Only prune dead or diseased material in late fall.

Impact on Next Year's Blooms/Fruit

• Removing Flower Buds: As discussed with spring-flowering shrubs, pruning at the wrong time can remove next year's flower buds, leading to a disappointing display.
• Reduced Fruit: Improper pruning on fruit trees can reduce the current year's harvest or negatively impact the formation of fruit spurs for the following year.

Essential Tools for Summer Pruning

Having the right, well-maintained tools makes summer pruning safer, more efficient, and healthier for your plants. Sharp, clean tools are paramount to making precise cuts that heal quickly.

• Hand Pruners (Bypass Shears): Your go-to tool for small branches up to 3/4 inch thick. Bypass pruners make clean, scissor-like cuts that are ideal for live wood. Fiskars Bypass Pruner is a popular choice.
• Loppers: For branches between 3/4 inch and 1 3/4 inches thick. Their long handles provide leverage for thicker cuts. Corona Extendable Handle Lopper can be very useful.
• Pruning Saw: For branches thicker than what loppers can handle. There are various types, including hand saws, folding saws, and pole saws. A folding pruning saw is great for portability.
• Gloves: Protect your hands from thorns, sap, and blisters. Look for durable, well-fitting gardening gloves.
• Disinfectant: Rubbing alcohol or a 10% bleach solution (1 part bleach to 9 parts water). Use to clean tools between cuts, especially when dealing with diseased plants, to prevent spreading pathogens.
• Sharpening Tool: Keep your blades sharp for clean cuts. A pruner sharpener is a worthwhile investment.

Tips for Successful Summer Pruning

To ensure your summer pruning efforts benefit your plants rather than harm them, follow these general guidelines. Timing, moderation, and proper technique are key to healthy pruning in the warmer months.

• Know Your Plant: Before making any cuts, identify the plant and research its specific pruning needs and flowering habits (old wood vs. new wood).
• Use Sharp, Clean Tools: Dull tools tear branches, making larger, slower-healing wounds that are prone to disease. Clean tools prevent the spread of diseases between plants.
• Make Clean Cuts: Cut just outside the branch collar (the slightly swollen area at the base of a branch) for larger cuts. For smaller cuts, cut just above a bud or leaf node that faces the direction you want new growth to go. Avoid leaving stubs.
• Prune in Dry Weather: This reduces the risk of fungal spores entering fresh wounds.
• Avoid Over-Pruning: Never remove more than 25-30% of a plant's total foliage in a single season. Excessive pruning stresses the plant.
• Remove the "Three Ds": Always prioritize removing Dead, Diseased, or Damaged branches first, regardless of the season.
• Remove Suckers and Water Sprouts: These vigorous, non-productive growths often emerge from the base or limbs of trees and shrubs. They waste the plant's energy and can be removed at any time in summer.
• Think About the Goal: Are you shaping, thinning, or encouraging fruit? Your goal will dictate your cuts.
• Monitor for Stress: After pruning, keep an eye on your plant for signs of stress (wilting, leaf drop) and provide adequate water, especially during dry spells.

Understanding the "Why" of Summer Pruning

Summer pruning is often called "green pruning" because you are working with leaves and new shoots. It's about redirecting the plant's energy during its active growth phase. When you remove leaves, you are temporarily reducing the plant's ability to photosynthesize and produce sugars. This reduction in energy can be precisely what's needed for certain outcomes.

For example, on a vigorous apple tree, summer pruning reduces the number of leaves that are diverting energy to shoot growth. This energy is then re-directed towards the developing fruit and the formation of fruit buds for the next year. It's a strategic way to manage the plant's energy budget.

Furthermore, increased light penetration from thinning the canopy during summer allows sunlight to reach fruit, enhancing color and ripening. Improved airflow also reduces the humid microclimates that fungi love, helping to prevent diseases.

In contrast, dormant pruning (late winter/early spring) aims to remove larger structural branches and encourages a strong flush of new growth in the spring because the plant has all its stored energy ready to go. Summer pruning, by removing active growth, tends to slow down growth and promote less vigorous, more manageable development.

Therefore, performing summer pruning is definitely okay and often highly beneficial, but it's a nuanced process. Knowing the specific requirements of each plant and understanding the distinct goals of summer pruning versus dormant pruning will lead to healthier, more productive, and more attractive plants in your garden. Always approach pruning with a clear purpose and sharp tools.