TL;DR

• Healthy clones display vibrant green foliage without yellowing, spotting, or curling—color is your first and most reliable indicator.
• Strong root development is non-negotiable: look for white, fibrous roots that have reached the edges of the growing medium.
• Inspect every clone for pests (spider mites, fungus gnats, aphids) and signs of disease like powdery mildew or root rot.
• HLVD (Hop Latent Viroid) testing has become essential—this invisible disease can slash yields by 30-50% and spreads silently through your entire garden.
• Stem thickness and node spacing reveal genetic vigor; avoid leggy, stretched clones that indicate stress or poor lighting during propagation.
• Always quarantine new clones for 7-14 days before introducing them to your main grow space, regardless of the source.

Why clone selection matters

Buying cannabis clones is one of the most consequential decisions you'll make as a cultivator. Unlike seeds, which offer genetic variation and the thrill of phenotype hunting, clones are supposed to be a sure thing—exact genetic copies of a proven mother plant. You're paying for certainty. You're paying for a head start. But that certainty evaporates the moment you bring home a sick, stressed, or infected clone.

I've watched growers lose entire crops because they got excited about a rare cut and skipped the inspection process. They saw the strain name they'd been hunting for months, handed over the cash, and drove home with a plant harboring spider mites that would colonize their entire flower room within three weeks. Others have introduced Hop Latent Viroid into previously clean facilities, watching their yields mysteriously decline cycle after cycle before finally getting tested and discovering the culprit.

The truth is that choosing healthy clones requires discipline. It requires slowing down, putting aside your excitement about genetics, and conducting a thorough evaluation. This guide will teach you exactly what to look for—and what to run away from.

Visual inspection: Reading the leaves

Your eyes are your first diagnostic tool, and foliage tells the story of a clone's recent life. Healthy cannabis leaves should be a vibrant, consistent green. Not lime green (which suggests nitrogen deficiency), not dark green with purple stems (phosphorus issues or cold stress), and definitely not yellow, spotted, or crispy at the edges.

Start at the top and work your way down. New growth should be bright and perky, reaching upward toward the light. If the newest leaves are pale, twisted, or stunted, the clone is struggling with something—whether that's nutrient problems, pH imbalance, or disease. These issues don't disappear when you bring the plant home; they compound.

Examine the undersides of leaves carefully. This is where many pests prefer to hide and where early fungal infections often appear first. You're looking for tiny specks (could be spider mite eggs or frass), webbing, white powdery residue, or any discoloration that differs from the top of the leaf. A healthy clone should look clean on both sides.

Pay attention to uniformity as well. If you're buying multiple clones of the same strain, they should look relatively similar. Dramatic variation in color, size, or leaf shape within a batch suggests inconsistent conditions in the nursery—or worse, genetic instability that could indicate a mislabeled cut.

Root health: The foundation of success

If a vendor won't let you inspect the roots, walk away. Roots are the foundation of plant health, and examining them is non-negotiable when selecting clones. Healthy roots are white or cream-colored with a fibrous, branching structure. They should smell earthy and fresh—not sour, swampy, or rotten.

The ideal clone has roots that have reached the edges of its container or rockwool cube without becoming severely root-bound. You want to see active root growth, those white root tips pushing outward, which indicates the clone has successfully established itself and is ready to transplant. Underdeveloped roots mean the clone was cut too recently or struggled to establish; you'll be nursing it along for weeks while it catches up.

Brown, mushy, or slimy roots are immediate disqualifiers. Root rot (usually caused by Pythium or Fusarium) is difficult to treat and easily spreads to other plants through contaminated water or growing media. A clone with root rot is not a bargain at any price—it's a liability.

Also check for consistency between the root mass and the foliage. A clone with lush top growth but sparse roots has been forced with excessive feeding or hormones, and it will struggle to support that foliage once it leaves the nursery's controlled environment.

Pest detection: What to look for

Pests are the silent hitchhikers of the cannabis world, and clone nurseries are their favorite transit hubs. The warm, humid conditions that clones need to root are also ideal for pest populations to explode. You need to inspect every clone like an airport security agent examining a suspicious bag.

Spider mites are the most notorious offenders. Look for tiny yellow or white specks on leaves (stippling damage), fine webbing between branches or on leaf undersides, and the mites themselves—they're about the size of a period at the end of this sentence. Use your phone's camera to zoom in if your eyes aren't what they used to be. A single pregnant female mite can found a colony of thousands within weeks.

Fungus gnats reveal themselves as small black flies hovering around the growing medium. While the adults are mostly harmless, their larvae feed on roots and can devastate young clones. If you see gnats flying, the infestation is already significant.

Thrips leave silvery, scarred trails on leaves and often hide in new growth. Aphids cluster on stems and leaf undersides, leaving sticky honeydew residue. Broad mites and russet mites are nearly invisible to the naked eye but cause distinctive leaf curling and bronzing that experienced growers learn to recognize.

Don't forget to check the growing medium itself. Lift the clone and examine the bottom of the container. Healthy media looks consistent and well-aerated. If you see larvae, mold growth, or anything moving, put the clone down and move on.

The HLVD crisis: Why testing is essential

Hop Latent Viroid has fundamentally changed what it means to buy healthy clones. This invisible pathogen has swept through the cannabis industry like wildfire, with some estimates suggesting 30-40% of commercial genetics are now infected. The truly insidious part? Infected plants often show no symptoms until they flower—when you discover your yields are 30-50% lower than expected and your cannabinoid content has plummeted.

HLVD cannot be detected visually in vegetative plants. A clone can look absolutely perfect—vibrant green, robust roots, pest-free—and still be carrying the viroid. Once it enters your garden, it spreads through contaminated tools, hands, and even potentially through root contact in shared reservoirs. One infected clone can compromise your entire operation.

This is why testing has become essential. Reputable clone suppliers now test their mother plants regularly using PCR testing, which can detect the viroid's genetic material even in asymptomatic plants. When shopping for clones, ask specifically about HLVD testing. When was the mother tested? What testing methodology do they use? Can they provide documentation?

If a supplier doesn't test for HLVD—or doesn't know what it is—find a different supplier. The money you save buying untested clones will evaporate when you realize your "verified cut" of a legendary strain flowers out at half the expected weight with minimal trichome production.

Structural indicators of vigor

Beyond color and cleanliness, the physical structure of a clone reveals its genetic vigor and the conditions under which it was propagated. These structural indicators help you predict how the plant will perform once it's in your garden.

Stem thickness is a reliable indicator of overall health. A sturdy, thick stem suggests the clone has been receiving adequate light and nutrients. Thin, weak stems indicate stretching toward inadequate light or nutritional deficiencies. These lanky clones will need support throughout their lives and often produce less than their genetics promise.

Node spacing tells a similar story. Tight internodal spacing—where branches emerge close together along the stem—indicates the clone received sufficient light intensity during propagation. Stretched, leggy clones with long gaps between nodes were reaching for light and will carry that structure forward, requiring more training and producing less flower per square foot.

Examine how the clone was cut and rooted. A clean, diagonal cut at the base promotes healthy root development. Jagged or crushed cuts invite infection. The rooting medium should be appropriate for the stage—rockwool, peat plugs, or appropriate soilless mix. Clones sitting in soggy, waterlogged media are at high risk for root problems.

Questions to ask your clone supplier

A legitimate clone supplier should welcome your questions and provide detailed answers. Their responses—and their willingness to engage—tell you as much about their operation as the plants themselves.

Start with provenance: Where do these genetics come from? A trustworthy supplier knows the lineage of their mother plants and can tell you whether they're working with verified breeder cuts, seeds they've pheno-hunted themselves, or cuts they acquired from other cultivators. Be skeptical of vague answers like "we got it from a guy."

Ask about their mother plant maintenance. How old are the mothers? How often are they tested for HLVD and other pathogens? What's their IPM (Integrated Pest Management) protocol? Professional nurseries have systems in place; hobbyists selling cuts often don't.

Inquire about the rooting process. When were these clones cut? What rooting hormone and method do they use? How long have they been rooted? Clones need 10-14 days minimum to develop adequate roots; anything sold sooner is being pushed out the door too fast.

Finally, ask about guarantees. What happens if the clone dies within a week? What if it tests positive for HLVD? Suppliers who stand behind their product will have clear policies. Those who don't are selling you a gamble.

The quarantine protocol

Even after conducting a thorough inspection and buying from a trusted source, every new clone should undergo quarantine before joining your main garden. This isn't paranoia—it's standard operating procedure for any serious cultivator.

Set up a quarantine space physically separated from your main grow area. This could be a small tent, a closet, or even a different room. The key is preventing any potential pests or pathogens from accessing your established plants. Ideally, you'd work in your main garden first each day, then visit quarantine—never the reverse.

Hold new clones in quarantine for a minimum of 7-14 days. During this time, inspect them daily for any signs of pests or disease that may have escaped your initial evaluation. Some pest eggs take several days to hatch; some fungal infections take time to manifest. This observation period catches problems before they spread.

Many growers use the quarantine period to apply preventive treatments—a light application of neem oil, insecticidal soap, or other IPM products. This creates an additional layer of protection. Some also send tissue samples for HLVD testing during quarantine if the supplier's testing documentation wasn't satisfactory.

Only after a clone has passed quarantine with a clean bill of health should it graduate to your main growing space. Yes, this adds time to your cultivation cycle. Yes, it requires extra space and effort. But it's far less costly than losing an entire crop to an infestation or infection that hitchhiked in on an exciting new cut.

Frequently Asked Questions

What's the most important thing to check when buying clones?

Root health and HLVD testing status. Roots tell you whether the clone is truly established and ready to thrive, while HLVD testing protects against an invisible threat that can devastate your garden without any visible warning signs.

How can I tell if a clone has spider mites?

Look for tiny speckling (yellow or white dots) on leaf surfaces, fine webbing between branches or on leaf undersides, and the mites themselves—minuscule moving dots about the size of a period. Use your phone camera to zoom in for closer inspection.

What does HLVD do to cannabis plants?

Hop Latent Viroid typically reduces yields by 30-50%, decreases cannabinoid and terpene production, causes stunted growth and reduced vigor, and often shows no symptoms until flowering. It spreads easily through contaminated tools and handling.

How long should I quarantine new clones?

A minimum of 7-14 days is recommended. This allows time for pest eggs to hatch and latent infections to manifest. During quarantine, inspect plants daily and keep them physically separated from your main garden.

What should healthy clone roots look like?

Healthy roots are white or cream-colored with a fibrous, branching structure. They should smell earthy and fresh, have reached the edges of the container, and show active white root tips indicating ongoing growth.

Should I buy clones from a dispensary or a dedicated nursery?

Dedicated clone nurseries typically offer better quality because clones are their primary focus. They're more likely to have rigorous testing protocols, proper mother plant maintenance, and knowledgeable staff. Dispensary clones can be hit-or-miss depending on their sourcing.

What's the best size clone to buy?

Look for clones that are 4-8 inches tall with at least 3-4 nodes and a well-established root system. Smaller clones need more time to develop; larger clones may be root-bound or stressed from extended time in small containers.