Tending Your California Native Garden in the Summer

Welcome to Summer - What makes the East Bay summer unique, and what to expect from your California native garden.

Watering Through the Dry Season - Finding the balance between healthy root development and preventing root rot.

How to Identify Overwatering and Underwatering - Visual signs to look for and how to use a soil moisture meter.

Managing Invasive Annual Grasses - Reducing the seed bank this season for an easier garden next.

Pruning, Deadheading & Seed Collection - What to leave, what to remove, and when to collect seed.

Watching the Garden Change - Seasonal cues that tell us fall (and planting season!) is just around the corner.

Welcome to Summer

Sticky Monkeyflower (Diplacus aurantiacus) is one of California's most important summer-blooming shrubs. Its tubular flowers provide nectar for Anna's Hummingbirds, Allen's Hummingbirds, Black-chinned Hummingbirds, large native bees such as bumble bees and carpenter bees, and numerous butterflies. It also serves as a larval host plant for the Common Buckeye (Junonia coenia), whose caterpillars feed on its foliage. Blooming well into the dry season, it provides an essential food source when relatively few native plants remain in flower.

Summer is the most challenging season for a new California native garden, but it's also one of the most rewarding. As days grow warmer, you'll begin to see buckwheats, California fuchsia, monkeyflowers, come into bloom, bringing in an abundance of native bees, butterflies, hummingbirds, and other beneficial pollinators. New growth above ground will slow or stop as the days warm, while underground your garden's root system will continue to develop in response to irrigation cycles. With thoughtful watering and some patience, your garden will continue building the deep root systems that support its long-term health.

Watering Your Garden During the First Establishment Year

Although California native plants are naturally adapted to our dry summers, newly installed plants are still developing the deep root systems that will eventually allow them to thrive with little-to-no supplemental irrigation.

The challenge during the first one to three years is finding the right balance, between providing enough water to keep root systems healthy and providing too much water. Young plants often need regular water through the summer months to fully establish, but California natives are also especially vulnerable to root rot if the soil stays wet and warm for too long.

Root rot occurs when saturated soil prevents oxygen from reaching the roots. Without oxygen, the roots become stressed, making them vulnerable to naturally occurring soil pathogens that thrive in warm and wet conditions. Once a portion of the root system has died, those roots cannot recover. As a result, the stems and leaves they once supported will begin to decline and die back. If enough of the root system is lost, the entire plant may eventually die. Fortunately, root rot is almost always preventable through proper irrigation. The key is to water deeply, then allow the soil to gradually dry before watering again, giving the roots access to both the moisture and oxygen they need to establish. This wet-to-dry cycle encourages roots to grow deeper while providing the oxygen they need to stay healthy.

One of the trickiest things about watering is that overwatered and underwatered plants can look surprisingly similar.

Pink-flowering Currant (Ribes sanguineum) is here showing signs of underwatering. This woodland species naturally occurs along moist forest edges and stream corridors, where its roots have access to consistent soil moisture. Although it is summer deciduous and will eventually enter dormancy, supplemental irrigation during its first few summers and during periods of extreme heat can help it remain lush and attractive well into early summer.

Signs that a plant needs more water:

• Leaves become limp or wilted.

• Leaf edges may become brown, dry or crispy.

• The soil several inches below the surface is dry.

• Leaves and stems droop during a hot afternoon but recover by evening are often responding normally to temporary heat stress rather than severe drought.

  
  

Whitebark Ceanothus (Ceanothus leucodermis), a chapparal species adapted to extremely low water, is here showing early signs of overwatering. Notice the yellowing and leaf drop on older, interior foliage while the outer canopy remains green. This is a common early indication that the root zone is too wet, and some roots have begun to die. If you see this pattern, reduce the frequency of irrigation and allow the soil to dry between watering events. If the problem is caught early, healthy roots can continue to grow while damaged roots are replaced. Remove the yellow leaves if desired, but avoid heavy pruning - the remaining foliage is still producing the energy the plant needs to recover. Monitor for new, healthy growth over the coming weeks, which is a good sign that the plant is recovering.

Signs a plant may be receiving too much water:

• Leaves remain soft but begin turning pale green or yellow.

• Older leaves on the interior of the plant begin yellowing and dropping while newer growth remains green. This is one of the earliest signs that the root zone is staying too wet.

• Growth slows despite regular irrigation.

• The soil remains damp for several days after watering.

• In more advanced cases, branches begin dying back from the tips as the root system declines.

A soil moisture meter is an excellent tool for taking the guesswork out of watering. Insert the probe 4–6 inches into the soil at the drip line (just outside the original root ball, or just under the tips of the outer branches). Check several locations around each plant. Water only after the soil has become moderately dry. After irrigation, the soil should be moist throughout the root zone, then gradually dry over the following days before the next watering.

Here, especially on the coastal section of the East Bay, our summer weather can be deceptive. Cool mornings and marine fog often keep soil moist longer than expected, while warm inland afternoons can cause plants to temporarily wilt as they work to reduce water loss. It's normal for some plants to look a little tired during the hottest part of the day, provided they recover by evening or the following morning.

If you're ever unsure whether a plant needs more water or less, please don't hesitate to reach out. A quick question early can often prevent a much bigger problem later, and I'm always happy to help clients interpret what they're seeing.

Managing Invasive Annual Grasses

Summer is the ideal time to reduce the abundance of invasive annual grasses and other unwanted non-native annual plants. As the weather warms, these species begin to flower and produce seed. Removing them before the seeds mature and turn brown is one of the most effective ways to reduce future infestations.

Gray Hairstreak (Strymon melinus) perched on an invasive annual grass. One of California's most adaptable butterflies, the Gray Hairstreak uses dozens of native plant species as larval host plants and visits a wide variety of flowers for nectar. While it can make use of human-altered landscapes, it thrives best where diverse native plants provide food and habitat throughout its life cycle.

The good news is that most invasive annual grasses have relatively short-lived seed banks. If you consistently prevent them from producing viable seed for one or two growing seasons, the number of new seedlings can drop dramatically. By the third year, maintenance is often very easy, as far fewer grass seeds remain in the soil waiting to germinate.

Prioritize removing invasive annual grasses first, followed by other unwanted non-native annual plants such as black mustard and thistles. If seed heads have already turned brown, carefully remove and dispose of the plants in your green waste bin rather than leaving them on the ground, where mature seeds can still be dispersed.

Maintaining a healthy 3-4 inch of mulch will further suppress new seed germination, conserve soil moisture, and protect the soil surface. As your California native plants mature, they will occupy more space, cast more shade, and naturally outcompete most invasive annuals. The result is a garden that becomes healthier, more resilient, and noticeably easier to maintain with each passing year.

Pruning, Deadheading, and Seed Collection

Summer is a time for light maintenance rather than heavy pruning. Many California native plants are still providing nectar, pollen, seeds, and habitat long after their peak bloom has passed.

Deadhead flowers if you prefer a tidier appearance or wish to encourage additional blooming in species such as sticky monkeyflower, California fuchsia, and yarrow. However, don't feel obligated to remove every spent flower. Many native plants produce seeds that feed birds and other wildlife or naturally reseed the garden.

Avoid major pruning during the hottest part of summer. Wait until plants have finished flowering and temperatures begin to cool before reshaping shrubs or removing significant amounts of growth. If a branch is dead, damaged, or poses a safety concern, it can be removed at any time.

Late summer is also an excellent time to collect seed from many native plants. Seed heads are ready when they have matured, dried, and begin to release seed naturally. You can collect seed to expand your garden, share with neighbors, or simply allow it to disperse naturally if you'd like your landscape to evolve over time.

If you choose to let plants reseed, remember that seedlings rarely appear exactly where you want them. Many California natives transplant surprisingly well when moved during the cool, rainy season. A volunteer seedling in one corner of the garden may become the perfect addition somewhere else.

Watching the Garden Change

Summer is a season of observation and learning. Notice which plants continue blooming, which naturally slow down or enter dormancy, and how wildlife responds to your garden throughout the dry season. As late summer gives way to fall, watch for California fuchsia to begin flowering, buckwheat seed heads to take on warm copper tones, coffeeberry and toyon fruits to ripen, and the first acorns to fall from our native oaks. These are all signs that California's planting season is just around the corner. When the first meaningful autumn rains arrive, the landscape awakens, and we'll once again be in the best time of year to plant California natives.