Bulbs for Warm Climates

[ Texas ]

Bulbs for Warm Climates

By Thad M. Howard

A comprehensive guide to bulbs that will grow in USDA gardening zones 8 and 9.



33% website discount price


7 x 9 7/8 | 288 pp.

ISBN: 978-0-292-73126-4

Bulb gardening in the southwestern and southern United States presents challenges unknown in cooler climates. Bulbs that turn Holland into a kaleidoscope of color droop and fade in our mild winters, hot summers, and uncertain rainfall. Yet hundreds of native and naturalized species of bulbs thrive in these same conditions and offer as many colors, shapes, and fragrances as even the most demanding gardener desires. These are the bulbs that Thad Howard describes in this comprehensive guide to bulbs that will grow in USDA gardening zones 8 and 9.

Writing from more than forty-five years' experience in collecting and cultivating bulbs, Howard offers expert advice about hundreds of little-known, hybrid, and common species and varieties that grow well in warm climates. His species accounts, which are grouped by family, describe each plant and its growing requirements and often include interesting stories from his collecting expeditions. Lovely color photos illustrate many of the species.

Howard also gives reliable information about refrigerating bulbs, using them in the landscape and in containers, choosing scented ones, making potpourri, buying, collecting, cultivating, and hybridizing bulbs, and dealing with pests and diseases. He concludes with lists of plant societies and suppliers and a helpful glossary and bibliography.

  • Acknowledgments
  • Introduction
  • Agavaceae
  • Alliaceae
  • Alstroemeriaceae
  • Amaryllidaceae
  • Anthericaceae
  • Araceae
  • Calochortaceae
  • Cannaceae
  • Colchicacea
  • Gesneriaceae
  • Hyacinthaceae
  • Hypoxidaceae
  • Iridaceae
  • Liliaceae
  • Orchidaceae
  • Oxalidaceae
  • Ranunculaceae
  • Tecophilaeaceae
  • Themidaceae
  • Trilliaceae
  • Zingiberaceae
  • Resources: Plant Societies and Suppliers
  • Glossary
  • Bibliography
  • Index

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This book is devoted to plants growing as monocotyledonous geophytes, a fancy way of referring to bulbs. Generally the word "bulb" means a swollen underground rootstock. Botanically, rootstocks are defined according to their morphology. They are true bulbs, corms, rhizomes, tubers, or tuberous roots. The onion is the most familiar example of a true bulb. Others in this book are bulbs of Calochortus, Crinum, Erythronium, Hippeastrum, Hyacinthus, Narcissus, Tigridia, and Tulipa.

In this book, little space is given to certain bulbs for one reason or another. Some bulbous plants, such as Gladiolus, Iris, and Dahlia, deserve books of their own, as do orchids. Many herbaceous perennials, including Hemerocallis, Hosta, and Kniphofia, are sometimes considered "bulbs," but they are not covered here. This book includes a broad spectrum of bulbous plants for warmer areas, particularly favoring the long-neglected bulbs of the Americas along with many bulbs from other countries.

I write about gardening in central, south central, and southeast Texas, an area that includes San Antonio, Corpus Christi, Houston, Beaumont, Austin, Waco, Tyler, and the Dallas-Fort Worth metroplex, in USDA zones 8 and 9. These zones also extend through the Southwest to the West Coast, as well as to the southeastern United States and Florida. Some plants discussed in this book can be grown farther north, in zone 7, while others can be grown in zone 10, but when I state that plants grow "in our area," "in our climate," or "here," I am speaking principally of zones 8 and 9, where we get some winter frost each year. It is too cold for plants that need a frost-free environment but not cold enough for those that require a minimum number of chill hours.

Bulbs are composcd of old leafbases and enlarged scales arranged concentrically. Thc roots and shoots develop from basal plates. The terminal shoots may contain only leaves, or leaves and flower embryos. They can be easily identified by slicing the bulb longitudinally.

Many though not all true bulbs have tunics, which can be useful in identification. Some bulbs are multitunicated, while others have a single layer. Some have papery tunics, and others have net-like, reticulated tunics that appear to have been woven. Non-tunicated bulbs consist of overlapping scales; some examples of these are Lilium, Fritillaria, and some Oxalis species.

True Bulbs versus Corms

In spite of older literature, Calochortus, Erythronium, Tigridia, and their allies (Alophia, Cypella, Eleutherine, Gelasine, Herbertia, Nemastylis, etc.) produce tunicated bulbs, not corms. The rootstocks of Erythronium are similar to the tunicated bulbs of species tulips. They are fleshy bulbs with several fleshy tunics, some of them forming what looks like the fang of a dog. Thus we have the term "dog-tooth violets." To my knowledge, there are no cormous native irids in the Americas, but there are some that grow from rhizomes (Iris, Neomarica) or fibrous roots (Sisyrinchium).

Corms resemble true bulbs but are solid in structure, with the growing bud atop the center or off to the side. The corm itself acts like an enlarged basal plate, producing roots from the sides or the bottom and a growing bud at the apex or the sides. Often corms are enclosed in tunics, just like true bulbs. Many plants annually form a new corm above the old corm; the old corm shrivels and is absorbed into the new one prior to dormancy. A few corms, such as those found in Ferarria, are not absorbed and will form a corm-chain. If the corms in the chain are separated, the slumbering old corm can be reactivated into growth and will in time produce a new mature corm that will flower once more. Examples of true corms are to be found in many plants of the Old World, such as Colchicum, Crocus, Freesia, and Gladiolus, and in New World plants such as Brodiaea, Bessera, Milla, and Tecophilaea. Some early taxonomists were careless in classifying the rootstocks, as many true bulbs were said to be corms. It is time to set the record straight.

Bulb Refrigeration

Bulbs are sometimes refrigerated to hold them back and extend the season. Tazetta narcissi can be retarded by planting at intervals until early spring, so that they will be in bloom over a long period. The same retardation works for lilies and gladioli, which can be held back for later planting. Tulips are refrigerated in warm climates to provide an extended winter situation, without which they will not bloom. Most bulbs do not need refrigeration and should be planted in the ground as soon as possible, so as to prevent deterioration. They are safer rooting in the ground than in a state of enforced limbo in a refrigerator.

Bulbs in the Landscape

Bulbs may be used to fill temporary needs. Once they have fulfilled those needs, we can then move on to something else. For instance, a bed of tulips can give way to gladioli, which in turn can give way to summer annuals. In this way one can use a given space several times during the year. Or one can naturalize or perennialize a given space for a show for a short period of the year and then allow this space to rest.

Bulbs for Dry Areas

Xerophytic bulbs, which are perfect for dry areas, include Iris albicans, Cooperia drummondii, C. pedunculata, C. morrisclintii, Schoenocaulon drummondii, S. texanum, Hymenocallis glauca, H. arenicola, Manfreda spp., Rhodophiala bifida, Zephyranthes lindleyana, Habranthus concolor, and Crinum album. These bulbs need little care and can be left to fend for themselves. In extremely dry situations they may need occasional watering. Most bulbs will want a bit more care than this. If you don't mind dragging the garden hose around during dry spells, you can try Allium, Brodiaea, Cooperia, Crinum macowanii, Hymenocallis acutifolia, and Sprekelia, as well as many Zephyranthes. These bulbs will get you through hard times.

Bulbs with Scented Flowers

Among the most fragrant bulbs are Cooperia, Crinum, Hedychium, Hyacinth, Hymenocallis, Muscari, Narcissus, Nothoscordum, Polianthes tuberosa, and some species of Schoenocaulon. If carefully selected, these plants can scent any spot in the garden. Avoid ill-smelling flowers such as some of the aroids, unless you just don't care. Their scent does not last very long (only a day), but it is enough to startle an unwary person.


Many small bulb flowers are well suited to being dried for potpourris. Put bulb flowers into a container along with some borax and work it in carefully around the flower, positioning the tepals the way you want them, and allow to dry for a few days. When you have enough of them dried, add some scented oil, and you then have the makings of a potpourri. This works especially well with small flowers such as crocuses and narcissi.

Inexpensive Bulbs

The monetary costs involved in accumulating a collection of bulbs cannot be ignored. Those finding it necessary to start off modestly should begin with simple things. Generally one will want to start with Dutch irises, anemones, and ranunculuses. With these you can have a nice little bulb garden the first year without straining the budget. At this point, you need to know how to go about enlarging your collection. At times it may be necessary to broadly hint to neighbors or strangers in order to obtain some treasure. The worst that they can do is to say no. If you offer to buy the plant or offer another plant in trade for it, the other party can decide if he or she wants to part with one. Often you will find that people are willing to share generously. In the past, this has been a strategy of mine, and it nearly always works.

Bulbs on Sale

Another strategy in collecting bulbs is to wait and see if they go on sale. The problem here is that you need to find a dealer who is willing to sell them at a discount when the demand for them drops off at the end of the season. A good dealer knows when to do this, but there are always a few die-hards who hang on to the bulbs until they are all dead. Such dealers make careful buyers wary of buying from them in the future.

Another problem in waiting for bulbs to go on sale is that the selections are smaller, and many bulbs perform poorly when planted late. You should inspect bulbs thoroughly to determine if they are still firm and succulent. Often they are hard and dead.

Collecting Bulbs in the Wild

If you happen to be fortunate enough to live in an area rich in wild bulbs and the opportunity arises, you might consider collecting them, provided that you can give them a chance to survive in their new environment, and provided that the local laws allow it and that you obtain permission. By all means collect them if they are in the path of future development, such as the widening of highways, and development involving bulldozers. Otherwise, take care to collect only seeds or bulbs that are plentiful, as we must conserve bulbs known to be rare. The best time to collect is when the plants have finished flowering. Then one may (preferably) collect seed. Growing new plants from seed takes a little longer, but in time there should be a good supply.

Bulbs from Specialists

In time you may want to look around for rarer bulbs not usually found in catalogs, and you may want to get in touch with other gardeners. These gardeners may be willing to sell some of their bulbs, or they may wish to trade for things that they don't have. Either way, a new bulb collector benefits. Many bulbs which otherwise would be unavailable are available from collectors in seed form. Joining a bulb society is a good way to get in touch with experienced collectors and growers.

Hybridizing Bulbs

One way to obtain bulbs that no one else has is through your own hybridization. Normally hybridization works only with members of the same genus, such as a Zephyranthes with another Zephyranthes, or a Crinum with another Crinum. This can start you on the road to a lifetime hobby. If you care to embark on this route, you must first obtain a variety of bulbs that will set seed. Accumulating them can take many years. Flowering the new plants from seed takes time, and the first hybrids may not amount to much. And finally one must learn to cull them ruthlessly in order to select only the best.

Geophytes from Hell: Weedy Bulbs

Most bulbs are a challenge for us to grow and keep, so it comes as a surprise that some bulbs are weeds and hard to get rid of. Some bulbs are tolerable and rarely become a problem, even though they can stray from where they were originally planted. We don't mind seeing a few bulbs reseeding themselves here and there about a garden as long as they don't get carried away with it. But within the genera Allium, Nothoscordum, and Oxalis are monsters that are waiting to get a foothold and are nearly impossible to eradicate. Perhaps the worst is Nothoscordum inodorum, a lovely fragrant thing with the tenacity of a bulldog. There are plenty of decent nothoscordums that mind their ways, so we don't have to deal with these rough ones. If you are so unfortunate as to have them get into your garden, you can deal with them with certain weed-killers carefully applied.


In warm climates, mulches are valuable in winter and summer. They stabilize the soil temperature, but more importantly they help retain moisture during dry spells and protect bulbs against cold or heat. Almost any kind of mulch will do, but ideally it should be a covering of leaves an inch or two deep in summer, and deeper in winter. An occasional light dressing of bug bait will discourage sowbugs, snails, and cutworms.

Withering Leaves

The most critical time for bulbs is when they have finished blooming. It is then that they must ripen their foliage in order to bloom the following year. While doing this they turn from green to yellow and become unsightly. Gardeners may want to conceal this process and permit the poor things to ripen in peace. It's the price that one must pay in order to keep them healthy. It's a tough time for them, but it doesn't last long. Some gardeners bind the ripening leaves or weave them into bunches, but to my mind this only draws attention to them. Actually the longer the ripening process, the bigger are next season's bulbs. Under no circumstances should the leaves be cut.

Diseases and Pests

Basal rot is caused by a Fusarium fungus that attacks dormant bulbs during warm, damp weather. Some bulbs are more resistant than others. The disease can be devastating, and explains why a successful planting sometimes fails to return a second season. It is best to avoid susceptible cultivars, while concentrating on cultivars known to be resistant to the fungus. Rhizoctonia, Sclerotium, and Sclerotinia are other forms of rot, and can also be treated with Benlate, a systemic fungicide and the chemical of choice.

Viruses. A number of viruses (mosaic, yellow stripe, white streak, and chocolate spot) can attack all amaryllids, irids, and many other bulbs. Virus diseases are easily spread by sucking and chewing insects, along with contaminated tools and the contaminated hands of gardeners and unthinking visitors who seem obsessed with handling and rubbing every leaf of every interesting plant that they see. Like the classic "Typhoid Mary," such visitors inadvertently transfer diseases as they go from one plant to another (including suspected virused plants), rubbing and feeling leaves. My advice for them is to look, but not touch, unless they are willing to wash their hands between plants. That should stop them. Virused plants generally do not recover from their ailment and should be destroyed. On the other hand, there are plants that show virus-like symptoms, but later seem to recover. This leads me to believe that some stresses often mimic viruses, but the plants outgrow them.

Thrips. While aphids, mealybugs, grasshoppers, slugs, and snails are usuallyblamed for the spread of viruses, I find that thrips are equally guilty. They can fly and are very active and so tiny that they easily go unnoticed, but they can disfigure flowers and disseminate virus diseases faster than any other insects but grasshoppers. They seem particularly attracted to white flowers, where they gather in large numbers. Spraying regularlywith insecticidal sprays is the best method to keep them in check during the warmest months. When they are not busy bothering daffodils, they will be found on Crinum, Hippeastrum, Hymenocallis, and Gladiolus, to name but a few flowers in their diet. Being so active, they can travel from virused plants in your neighborhood to your garden and back again. Perhaps the solution to viruses is to breed plants resistant to them.

Nematodes can be commercially devastating to daffodil growers, particularly in sandy soils. Formerly nematodes could be controlled by sterilizing the soil with chemicals such as Vapam, but it has been outlawed by the Environmental Protection Agency and is no longer available. It may help to plant nematode-deterring plants such as marigold and rye, which can later be turned under.

Bulb mites are pests that attack plants already under stress. They rarely bother healthy plants, but woe to a plant that already has problems. They multiply rapidly and can kill a plant in a short time.

Red spider mites are particularly attracted to irids. Spraying or dusting with insecticides works. There are all sorts of sprays, but powdered sulfur is also valuable in treating them. One must begin early; by the time you have discovered that you have spider mites, it is already late.

Snails and slugs. These slimy things are noxious, but can be controlled with bug bait. Beer is also recommended for snails and slugs, but I have never tried this. It is said to work.

Grasshoppers are killed by liberal dusting, or with baits.

Mealybugs and aphids are controlled by spraying with insecticide, but it must be repeated frequently as they can be very bothersome.

Mammalian pests. Deer and rabbits can temporarily be kept away from bulb plantings with applications of blood meal. They hate it. But it must be reapplied after each watering or rain. This can get to be a bit of a nuisance in rainy spells, but it is a harmless way to add extra fertilizer to plants at odd times. One can also get similar results with sulfur powder or a mixture of blood meal and sulfur.

Garden Tools

There are many kinds of garden tools for digging, but my favorites are a good sharp shooter spade and a sturdy garden fork, preferably with all-metal handles. These can be hard to come by and cost a bit more than those with wooden handles, but they are well worth the extra effort. For lesser hand work, I prefer aluminum trowels and forks. The kinds with wooden handles don't last long. You will find good quality tools paying for themselves many times over in money saved by not buying new ones again and again. I always place a bit of fluorescent tape around the handles in order to find them quickly should I leave them lying about.

Because this book employs a mixture of common and technical terms, a glossary has been included to smooth over the rough edges. I hope that you find it useful.

Winner of the International Bulb Society's Herbert Medal, Thad M. Howard, who lives near San Antonio, has discovered more than thirty-five new species of bulbs in Texas, Mexico, Guatemala, Brazil, and Argentina. He is also the author of many professional papers on bulbs.