Bulbs are little self-contained plant making machines. Magic! Right now, the bulbs pictured in this post are flowering beautifully in my spring garden. Yay! Here’s an introduction to planting and caring for bulbs in the home garden.
Did you know?
True bulbs like the easily recognisable onions, daffodils, and lilies are made of fleshy layers surrounding an immature internal stem and/or leaves. Other “bulbs” that aren’t really true bulbs include corms, tubers, and rhizomes.
Corms, like freesias and gladioli, are solid and sometimes even woody. When you plant a corm, it’s usually consumed in growing the plant and replaced with new child corms at the end of the growing cycle. Stem tubers, like the potato, and root tubers, like dahlias and kumara, are thickened underground growths with growing points (eyes) from which new plants can grow. Rhizomes, like irises, turmeric, and ginger, are fleshy underground stems that can grow into new roots and shoots of their own.
Bulb Selection
Selecting Healthy Bulbs
Healthy bulbs start with healthy source plants. Once lifted, storage conditions and time will affect the probability of planting success. Like stored seeds, the longer a bulb is stored, the lower the chances of growth. A good healthy quality bulb will be firm to the touch, with no signs of rot or mould. Sizes vary by species and variety, but within the same plant type, bigger bulbs typically grow and flower more prolifically in their first season than smaller bulbs.
Growing Right Plants for the Right Places
As with any plant, choosing varieties that you like that also suit your climate, aspect, and garden conditions will help with planting and growing success. There are bulb plants for sun and for shade, but almost every variety of bulb will prefer free-draining soil. Wet soils are prone to bulb rot. In our heavy clay soil, most plants need to be raised up a little and any bulbs are happiest in pots and planters.
Planting Your Bulbs
Keeping Track of Bulb Varieties and Details
When you buy (or are given) new bulbs, keep the packaging label or take note of the variety and any specific planting requirements. Store this with your bulbs until planted, as it’s important to plant at the right time of year and in the best conditions for growing success. Once planted, transfer the label to your garden records or transcribe the key details for future reference. This is especially handy for lifting, sharing, or future propagation. I like to use my mobile phone to take photos of labels for easy future reference. Check out our other tips for garden record keeping.
Planting Cycle and Season
Not all bulbs have the same planting cycle. Spring blooming bulbs like to be planted after summer when the weather and soil are cool. Summer blooming bulbs like to be planted in the springtime when any danger of freezing conditions has passed. Some bulbs benefit from a pre-planting chill to simulate natural dormancy conditions before planting.
Planting Area and Preparations
Prepare your planting area or container for planting. Bulbs benefit from good quality free-draining soil and are prone to rot in soggy soil. As noted in selection above, aspect will depend on the plant and variety. Most bulb plants prefer some sunshine for best growth and blooms.
Planting Bulbs
Bulbs like to be planted to different depths depending on the type of plant. Check for your specific varieties for best results; however, a good general rule of thumb is that many (not all) bulbs like to be planted roughly twice as deep as the bulb is tall.
Don’t forget to plant them right-side-up. If you can figure out which side is up by looking at the bulb, you can try sideways planting and keep your fingers crossed – nature often sorts itself out! Many have an obvious top and bottom, but some can be a bit mysterious. Tubers and rhizomes are a little special, and are happy sideways. I also usually chit or sprout these before planting or propagating out, like I do with kumara. Those are yams sprouting pre-planting in the photo below.
Record your bulb plantings in your garden records and/or with plant markers so that you don’t lose track of what’s where when things are dormant. If you know you’re going to lift your bulbs, you can use basket-style bulb plating containers to make removal easier. If you have local wildlife (or curious garden pets – beware, some bulbs are poisonous), you can plant them under wire or sturdy plastic mesh to limit digging.
Plant Care
Most bulb plants are relatively low maintenance during their growth period. Yay! See our troubleshooting tips below if things aren’t quite going as expected. Good soil plus a light feeding just after they sprout and again after flowering is usually plenty. An occasional drink, general weeding, light mulching, and control of any pesky bugs and critters is all the help most bulbs need. Snails and slugs are common pests for routine control.
As they finish flowering, you can cut off spent flower stalks if you’d like, but leave the leaves to feed the bulb. These will die down naturally once they’ve done their duty replenishing the bulb and/or any new bulbs in preparation for the next growing cycle. Because most bulb plants will naturally die back, they work well for layered plantings and adding season interest with offsetting dormant varieties of bulbs or other plantings.
Propagating from Bulb Grown Plants
Lifting vs. Naturalising Bulbs
Depending on where your growing climate and type of plants, you may need to lift and store your bulbs between growing seasons. If you’ve lifted your bulbs for seasonal storage, keep them with free air circulation in a cool dry place until it’s time to plant again. If you are naturalising your bulbs in situ, you can set and forget; however, lifting and splitting every few years can help improve flowering and allow you to expand your garden for free. Win-win! Many of our bulbs seem to stuggle with the cool wet winters, so we move pots to more sheltered spaces or lift the bulbs for storage.
Baby Bulbs
Bulbs can develop small offsets or bulblets (little baby bulbs) next to the root area of the parent bulb’s basal plate. Both the bulb and the bulblets can be replanted to grow. Similarly, spent corms develop a new corm or multiple cormlets (child corms) to grow the next generation. In additional to natural growth, you can expedite corm development through scaling propagation methods.
Some type of bulbs can be allowed to mature, in one cycle or multiple seasons, until they divide internally into offsets, splitting the parent bulb into clumps of internal offspring. These bulbs can be lifted and separated for replanting. Many gardeners will be familiar with this method for growing garlic (the individual cloves are offsets), but it applies to many other bulb plants as well.
Bulbs that Set Seed
Some bulbs will set seed if you leave the flower stalks intact. You may need to grow the seed significantly longer in order to develop a mature plant of equivalent size to a planted bulb, but that all depends on the type of plant. Some grow wonderfully, like our seed-grown dwarf dahlias in the photo below. Those also produced great tubers in their first year, too! We’ll explore seed starting, division, and other propagation methods in future posts.
Bulb Troubleshooting Tips
Planted Bulbs Not Sprouting on Expected Schedule
If your bulbs don’t sprout when expected, review your garden notes. Double-check that the varieties you’ve chosen are well suited to your climate and their planting conditions in your garden. If everything looks good on paper, but the plants haven’t emerged, it may be a temporary delay. Don’t give up hope just yet – seasonal variations, micro climates, and other factors will affect growth. I’ve been known to get a little impatient and dig down to check, only to discover things are starting to sprout just fine on their own time.
Planted Bulbs Fail to Sprout
Sometimes, it’s not just a waiting game, though. Failed germination is always a bit of a bummer, but it happens. If your bulbs don’t sprout at all and there are no obvious culprits, further trouble shooting is needed if you want to try again for better success.
As noted above, bulbs like different planting depths depending on the type of plant. Planting too deep can cause failure to sprout and/or rotting. Planting too shallow might leave them overexposed to harsh conditions or sneaky pests before they sprout.
Although you can find bulbs for a variety of different garden aspects, soggy ground is usually a bulb killer. You can try to improve poorly drained soils with sand or raise the beds, but sitting in soggy wet soil will usually lead to rot.
If, like me, you use containers, these are handy for avoiding wet soil but are a little more vulnerable to other conditions. Bulbs planted in smaller portable pots may benefit from being placed in the shade to limit temperature fluctuations until they sprout.
If the temperature of your growing climate is suited to naturalisation, but your planting area has a tendency for soggy dormant seasons (like many parts of our garden during our wet wet winters) lifting may still be beneficial. On the flip, if you have sizzling summers, summer dormant bulbs may also benefit from lifting so that they don’t roast.
Planted Bulbs Have Sprouted but Growth is Poor
If new bulbs sprout but fail to impress with growth and/or blooms and there are no obvious issues with variety, pests, or disease, it can be tricky to figure out what wrong. For troubleshooting ideas, a lack of chilling (such as an unusually warm winter/spring) or other adverse growing conditions (poor variety for location, low quality soil, poor aspect, over shading, crowding, etc.) may be the culprit(s).
Existing Bulb Plants Declining in Vigour
If naturalised bulb plants were initially performing well but are declining over the years, early leaf removal (low bulb storage), decreasing soil quality, increasing shade from nearby maturing plantings, or overcrowding may be factors. To help avoid overcrowding bulbs, you can lift and split naturalised plantings every few years, as noted above.
