Bulb Guide: How to Tell if a Bulb is Healthy

Growing bulbs can quickly become an addiction, one that many gardeners already have. These powerhouses deliver the most beautiful plants, all sprouting from a tiny storage vessel.

Bulbs are slightly different in structure from plants you may be used to growing. It’s important to understand a few bulb basics, starting with viability. Before planting (or preferably, before purchasing), you need to know whether your bulb is healthy and capable of growing into the plants you’re looking forward to.

If you want to tell if your bulb is healthy, there are a few telltale signs to watch out for. Discard any problematic bulbs and plant the rest for a healthy and thriving garden.

Signs Of A Healthy Bulb

It can be tricky to differentiate between a healthy bulb and an unhealthy one without getting up close and personal. Most signs of a healthy bulb are just the absence of indicators that it is unhealthy, but there are a few other pointers to look out for.

Firm To The Touch

The first sign of a healthy bulb is a firm texture. Bulbs contain plenty of moisture and nutrients, ready to sprout when the time comes. This moisture keeps them firm and strong, holding up well to a gentle squeeze or toss around.

Don’t be afraid to press into the bulb to test the firmness and check for weak spots. You can also test their weight – they shouldn’t feel lighter than usual for their size. As long as you don’t break into the bulb itself, you won’t do much damage. If any part of the bulb does feel soft and mushy when squeezed, it is no longer viable.

No Signs of Disease

Bulbs are susceptible to several nasty diseases that can quickly eat away at the tissue and inhibit growth. They can pick up various fungal or bacterial diseases from the soil, incorrect storage, or even infected bulbs nearby.

Depending on whether the issue is bacterial or fungal, the signs of disease may look slightly different. But generally, they’re easy to spot, producing an overall sickly appearance. Mushy or sunken areas, moldy patches, black discoloration, or a slimy coating indicate a disease problem on your hands.

Diseased bulbs shouldn’t be planted or kept near any viable bulbs in storage. If a few bulbs have been stored close together, watch them for signs of spread. If the problem does continue, you may need to get rid of them all, as unfortunate as it may be.

No Signs of Pests

Disease is one of the main concerns when buying or bringing bulbs out of storage. But you shouldn’t discount pests wrangling their way into your bulbs to feed on their tasty flesh.

Common garden pests like aphids and thrips are known to feed on bulbs in the garden and in storage. This damage impacts the areas they feed on and makes the bulb more vulnerable to fungal diseases that seal the deal on viability.

Bulb fly larvae are also incredibly damaging, overwintering inside bulbs and eventually killing the entire plant. Look out for tunnel marks and soft spots on the bulbs, or watch for the flies themselves near where your bulbs are located.

Less easy to spot but equally as problematic, bulb mites feed on bulbs and reproduce rapidly, quickly taking over an entire crate. These pests are tough to get rid of, so it’s essential to discard them as soon as you spot them and watch out for signs of spread.

One or two creepy crawlies don’t always signal a damaging bulb pest. But if you spot any discoloration, tunneling, or soft spots on your bulbs, discard them immediately.

Not Shrivelled

Healthy bulbs store a lot of moisture, or at least they should when stored correctly. If your bulbs are stored in the incorrect medium or in high-temperature environments, they can quickly lose this moisture and shrivel up.

A partially shriveled bulb isn’t always the end of the world. If the issue is not too severe, it is possible to rehydrate your bulbs by popping them in a bucket of water overnight. However, this doesn’t guarantee that the plant will grow successfully or even flower if the inner parts of the bulb are badly damaged.

If your bulbs are so dry that they easily break apart and almost disintegrate when you handle them, rehydrating isn’t likely to save them. Discarding these and adjusting your storage methods for next season to avoid disappointment is best.

Sinks In Water

Even if you don’t notice too many signs of trouble on the outside of the bulb, there may still be issues inside the bulb that affect viability. Problems with pests, diseases, or storage can cause the inside of the bulb to rot and become mushy without you even knowing it.

If you suspect an issue – perhaps the bulb feels lighter than usual or isn’t as firm as you would hope – there is a simple test to help you answer the question of viability: toss your bulbs in a bucket of water before planting. Those that sink are probably viable. If they float, don’t plant them.

You can also complete this test without planting afterward if you clean and store the bulbs correctly to prevent fungal growth.  

Large In Size

The next sign is not necessarily an indicator of a healthy bulb but does translate to better growth after planting.

Bulbs that are larger in size typically grow into fuller plants that flower more prolifically, thanks to the head start they receive from additional nutrients and a robust root system. Smaller bulbs can still be planted (unless you notice any signs of issues, as mentioned previously), but they may take a little longer to get going or won’t grow as successfully as larger bulbs.

If you’re storing bulbs you’ve pulled from the garden, you can plant them all, no matter the size, and hope for the best. However, if you’re buying new bulbs and want the highest possible chance of success, always look for the biggest bulbs.

Not Stored For Too Long

The final marker of a healthy bulb relates to age. Bulbs only last so long in storage before they lose their vigor, lacking the energy to spring up after planting.

It’s generally best to plant your stored bulbs within about six months – usually not an issue if you’re replanting the same bulbs year after year. However, they can last up to a year at a push if you risk a couple not entirely taking.

If your bulbs have been stored for longer than a year, it may be an uphill battle to get them to grow successfully. It’s not impossible if they’re firm and show no signs of disease, but you’ll have a much easier time planting healthy new bulbs instead.

That also means there shouldn’t be any delay in planting your newly purchased bulbs. As a forgetful gardener, I’ve left a few bulbs in storage far past their planting time, hoping to wait for next year instead. Unfortunately, bulbs aren’t designed to last that long out of the ground.

What To Do With Unhealthy Bulbs

As tough as it may be, unhealthy bulbs need to be discarded, particularly if you are dealing with pest and disease problems. These issues can quickly spread to other healthy bulbs in storage or, worse, to the soil once you’ve planted.

Ignoring an issue can become a yearly headache, so it’s best to discard any unhealthy bulbs (or destroy them if you want to stop pests from spreading). Rather, use your energy to nurture the healthy bulbs you have left, keeping the rest of the plants in your garden safe at the same time.

Final Thoughts

Before planting any bulb – whether newly purchased or pulled out of storage – make sure you know what you’re dealing with. These signs will tell you whether your bulbs are ready to go or better off in the trash.