Arboricultural Consulting in the Mid-Atlantic
Zastrow Arborists, LLC
We speak
for the trees.
Tim and Mary Zastrow combine decades of training and field experience to provide thoughtful, science-based arboricultural consulting, rooted in stewardship and long- term care.
Who We Are
Meet Tim and Mary Zastrow
Rooted in Science
Tim and Mary Zastrow are consulting arborists with backgrounds in entomology and a shared commitment to understanding living systems. Their early work studying insects and ecological relationships shaped a lifelong respect for the complexity of trees and the environments they inhabit. Together, they approach arboriculture as an opportunity to assist tree owners and managers in caring for some of the most amazing organisms on the planet.
Experience and Advocacy
Tim is a Registered Consulting Arborist (ASCA since 2014), Board Certified Master Arborist (ISA since 2008), Maryland Licensed Tree Expert, and Qualified Tree Risk Assessor (ISA since 2013). He has 40 years of experience with tree assessments and diagnostics, tree protection during construction, risk assessment, and all aspects of tree and shrub care. Mary complements his skills with her wholistic perspective and hands-on horticultural experience, including her work in sustainable cut flower farming. She is a Certified Arborist and Qualified Tree Risk Assessor (ISA since 2019). Through Zastrow Arborists, they provide prescription-driven guidance for residential and commercial properties, advocating for the informed decisions that protect both trees and the people who live alongside them.
Through a tree’s eyes
What would a tree ask for?
Time and experience
Respect in Old Age
Trees change as they age, and so should how we care for them. Older trees often carry greater structural complexity, ecological value, and emotional significance—but they can also face increased stress, decay, and risk. Respecting an aging tree means understanding its history, its limits, and its role in the landscape today. Through careful assessment and informed recommendations, we help extend the life of mature trees while balancing safety, stewardship, and long-term value.
Before growth begins
Right Plant, Right Place
A tree’s success is largely determined before it ever goes into the ground. Soil conditions, available space, sun exposure, and surrounding infrastructure all influence how a tree will grow—and whether it will thrive or struggle. Selecting the right species for the right location reduces future conflicts, lowers maintenance needs, and supports healthy development over decades. Thoughtful planning at the start leads to stronger trees and more resilient landscapes.
Below the surface
Informed Arboriculture
Planting depth matters more than most people realize. Trees planted too deeply may survive for years before declining quietly or suddenly breaking at the base or uprooting. Proper planting depth allows roots to breathe, spread out, and anchor the tree naturally. Whether correcting past mistakes or ensuring new plantings are done correctly, we can help get this detail right to protect tree health and stability from the ground up.
Energy and balance
Vibrant & Healthy Foliage to Make Sugar
Leaves are where trees turn sunlight into energy. Healthy foliage supports growth, resilience, and recovery from stress events. Poor leaf function is a sign of deeper problems. Soil conditions, pruning practices, insect and disease activity, and nutrient availability all influence leaf vitality. By supporting the systems that sustain healthy leaves, we can help trees produce the energy they need to be strong and remain stable over time.
Living systems
Friends
Trees exist within living communities. Birds, insects, fungi, and soil organisms all play roles in supporting tree health and resilience. These relationships—often unseen—help regulate pests, recycle nutrients, and strengthen ecosystems. Encouraging biodiversity and respecting these natural connections allows trees to function as part of a larger, balanced system rather than in isolation.
Shared benefits
Care Over Time
Trees offer more than beauty. Their shade cools neighborhoods, protects soils, shelters wildlife, and improves the comfort of the spaces we live and work in. Preserving trees so they can continue providing these benefits requires foresight—especially during development and land-use changes. Thoughtful protection ensures that trees remain assets to both people and landscapes for generations to come.
What we do
Services we provide
Risk Assessments
We evaluate trees for structural integrity, relative health, and the surrounding site conditions to assess risk potential and provide options for mitigation. We can do this for individual trees on private sites or large groups of trees in public places.
Mature Tree Preservation
To better balance the benefits of mature trees with the elevated risk they may pose, we provide recommendations- pruning, cabling, or other recommendations – to enhance stability and extend tree life.
Tree & Shrub Inventories and Management Plans
We document, tag, and map trees & shrubs to create clear organized records to support planning, compliance, and long-term management decisions. We are also able to draft multi-year management plans, help prepare statements of work for contracts, and assist with budget forecasting.
Selection Recommendations
Choosing the right tree or shrub matters. Drawing on our long experience we can recommend species that will fit your site, goals, and budget, thereby promoting longevity, resilience, and appropriate levels of maintenance.
Tree Protection During Construction
From pre-construction evaluation to prescribing appropriate care, we help protect valuable trees through proactive strategies to minimize tree damage and support continued health.
Boundary Issues
Trees do not recognize property lines. We provide guidance and documentation to help resolve disputes, and care plans to minimize encroachment and appropriately manage risk.
Talk Soon
Contact us today
Have a question about a tree, a site, or a specific concern? We’re happy to listen. Reach out to start a conversation about thoughtful, science-based tree care and long-term stewardship.