Better Selections Now!
A guide to choosing superior garden plants
Blue Sterling's Newsletter

Friday, March 8, 2002

T he Attack of the Mutant Witches Broom

Elves, dwarves, pygmies. Little Ann and her friend Little Jamie. And let's not forget St. James! Where do unusual conifers like these come from?

It's pretty unlikely for a nursery owner to wake up one day and decide to hybridize a new conifer cultivar. The payoff just isn't there at the end of the year. Or in the case of dwarf conifers, the payoff isn't there at the end of the decade. So, conifer cultivars are much different from say, roses, which are constantly hybridized by nursery growers.

New conifer cultivars originate in a few specific ways. Some are mutations that originated as seedlings. Others are mutations, also called "sports" on normal plants. Still others are propagated from odd looking masses of congested foliage called witches' brooms.

Seedling mutations are occasionally discovered in nurseries but are usually found in the wild. Unless a nursery is dedicated to growing unusual plants, seedling mutations are usually culled out - that is they are cast aside to make room for efficient production of bread and butter plants. Blue Sterling is focused on the unusual, so when we spot a mutant plant we save it rather than toss it away!

Seedling mutations differ from the standard species in one or more of these areas: Vigor, color, habit, foliage. Some seedling mutations grow faster than normal and are valuable to foresters. Others grow much slower than typical and offer great utility for smaller modern landscapes.

Color mutations remind us that conifer variations are endless. Golden plants may exhibit a white flecking, green plants may have an aberrant leaf that is pure snow white. And the variations continue. We perform trials in the Idea Garden and discover which golden (or blue, or variegated) plants are best suited to our climate. We grow several similar cultivars for years before determining which is truly superior. This selected cultivar becomes the standard we use to evaluate any new plant with similar attributes. We test every new cultivar in our Idea Garden to determine what new plants will appear in our catalog. And eventually make their way to your garden.

Conifers with narrow habits are an important ingredient in small gardens. Fortunately, seedling mutations are usually very stable. You don't have to worry that your narrow Juniperus communis 'Compressa' is going to fill out in a few years.

Other conifers have globose habits. Almost everyone has a favorite weeping conifer, and we're no exception. Of course our favorite changes about every week or two! Some classic seedling raised habit mutations are Chamaecyparis obtusa 'Nana Gracilis' (below) and Chamaecyparis obtusa 'Dainty Doll'.

All conifer seedlings begin life with different type foliage than mature plants. This is called juvenile foliage. Well, some conifers just don't want to grow up and keep this juvenile foliage throughout their life. An example you may be familiar with is the soft needle Atlantic white cedar cultivar, 'Heatherbun'.

Nobody is certain what causes seedling mutations in conifers. Seedling mutations grow to become healthy mature plants. These mutations occasionally produce viable seed. The miniature hinoki 'Elf' originated as a seedling of the larger 'Nana Gracilis'. Seedling mutation cultivars are quite stable and can be asexually propagated.

Not all new conifers cultivars originate as seedling mutations. Many of the variegated plants you enjoy started out as sports on otherwise normal plants. The famous juvenile foliage Rheingold arborvitae started out as a sport as well. These sports may be caused by a virus or another agent, but as with seedling mutations the plant remains healthy. When one of our managers identifies an intriguing sport he observes it for a while to see if the mutation is stable. If the sport looks unique, Andy, our Propagator takes some cuttings from the aberrant foliage and we wait to see if it lives! Cultivars that originate as sports seem more apt to revert to their previous state than seedling mutations do. We watch our sports for years before deciding if they are sufficiently unique and stable enough to be introduced to your garden.

Want to make a gardener smile? Tell her you have a witches' broom in your yard! This odd phrase describes masses of dense and slow growing foliage that appear in many plants, but are most often seen in pine, spruce and firs. Brooms are a great source of dwarf and dense cultivars. You may have read of witches' brooms damaging fruit trees. This phenomenon seems totally benign in conifers and is not linked to pathogens or parasites. If you're on a road trip with kids, get them in the habit of looking high into the trees along the highway for "brooms". When they see how high in the trees these masses appear, they will probably beg you to stop the car so they go climbing! You'll undoubtedly have new respect for the brave souls who scale trees to collect a sample or seed! Yes, seeds. Many witches' brooms produce live seed which can be a great source of unusual cultivars. Dr. Sid Waxman of the University of Connecticut introduced some popular dwarf white pine cultivars like 'Blue Shag' he grew from witches' broom seed. Which brings us full circle in our exploration of the origins of dwarf and unusual conifers.