The botanical world is full of beautiful, remarkable sights and processes that can leave us in awe. But there are also some peculiar plants, mutations, and botanical diseases and disorders that can spark our curiosity or even send a shiver down our spines.
Our horticulturalists at the William T. Kemper Center for Home Gardening have compiled this list of strange and fascinating botanical oddities for plant lovers to explore during this Halloween season.
Witches’ Brooms
Witches’-broom on hackberry (Celtis); caused by a combination of eriophyid mites (Acari) and the powdery mildew fungus. Photo courtesy of Plant Finder/Missouri Botanical Garden.
Have you ever noticed a dense, tangled mass of leaves and twigs high up in a tree? You may have seen a witches’ broom.
They often form in evergreen conifers or deciduous tree species and commonly appear as a proliferation of small twigs with disfigured or stunted leaves emanating from a single point high in a tree’s canopy, but they can also be found on shrubs and other plants.
Witches’ broom can result from a number of factors: fungal infection, viral infection, bacterial infection, damage from insects or mites, genetic mutations, or adverse environmental conditions.
Some horticulturists seek out witches’ brooms to collect for their potentially desirable traits such as dwarf, compact, and dense growth habits. However, only witches’ brooms resulting from a genetic mutation can be successfully propagated.
Witches’ broom on rose (Rosa) caused by rose rosette. Photo courtesy of Plant Finder/ Missouri Botanical Garden.
Did you know these cultivars originated from witches’ brooms?
Picea abies ‘Nidiformis’, a dwarf Norway spruce cultivar that is sometimes called birds nest spruce due to its round and flattened shape.
Thuja occidentalis ‘Bobozam’, a popular dwarf American arborvitae cultivar that is often sold under the name Mr. Bowling Ball.
Morus rubra ‘Super Dwarf’, a unique red mulberry that only reaches 3′ tall.
Photos courtesy of Plant Finder/ Missouri Botanical Garden.
Resurrection Fern
Resurrection Fern
Resurrection Fern (Polypodium polypodioides). Photo courtesy of Plant Finder/Missouri Botanical Garden.
Polypodium polypodioides, commonly called resurrection fern, is an incredible species of fern native to much of the southern United States, including southeastern Missouri.
Resurrection fern (Polypodium polypodioides) growing on a tree. Photo courtesy of Plant Finder / Missouri Botanical Garden.
Resurrection fern is most commonly found growing epiphytically on the branches of trees, using them as a support structure, but can also grow on rocky ledges. Because it grows in places with little to no soil, this fern has adapted to drying out almost completely and will enter a dormant state until rain returns, with the fronds curling inward and taking on a greyish-brown coloration.
The plant can lose up to 97% of its water and still be alive. After a rainfall, the plant will take up water quickly, rehydrating its fronds and resuming normal levels of photosynthesis in as little as 24 hours.
Fasciation
Fasciation seen in celosia pulled out of one a bed. Photo courtesy of Daria Mckelvey/Missouri Botanical Garden.
This curling, twisted growth may look like it is the result of a curse, but it is actually a fairly common botanical oddity.
Fasciation seen in celosia pulled out of one a bed. Photo courtesy of Daria Mckelvey/Missouri Botanical Garden.
Fasciation seen in the asteraceae family. Photo courtesy of Daria Mckelvey/Missouri Botanical Garden.
Euphorbia dendroides (Cristate form). Photo courtesy of Daria Mckelvey/Missouri Botanical Garden.
Similar to witches’ broom, this deformation can be caused by damage to a terminal growth point on a plant due to infection, insect damage, genetic mutation, or environmental conditions.
Fasciation can occur on any part of virtually any plant, but it is perhaps most noticeable on flowering structures. The abnormal growth is typically wide and flattened, with a curled or twisted appearance.
Stable fasciation that is the result of a genetic mutation can be quite desirable for plant breeders and collectors. Cockscomb (celosia) are purposefully grown for their fascinating fasciation.
Crested euphorbias are also extremely popular and are sometimes grafted onto nonfasciated rootstock to improve vigor and show off the crested shape of the fasciated growth.
Slime Molds
Slime molds (sometimes called dog vomit fungus) are primitive organisms with an identity crisis as they share many characteristics with fungi and are still placed in the Kingdom Fungi by some authorities, but others now place them in the Kingdom Protista (Protoctista), division Myxomycota.
They typically appear in mulches during the summer after rainfall, forming large, colorful colonies on the surface of mulch around trees, shrubs, and perennials. They can range in size from several inches to 2 feet or more in diameter. Color also varies, but the most noticeable form appears as a bright yellow, slimy mass when fresh.
They can “flow” slowly across the mulch a distance of several feet, ingesting dead matter as it goes. They may appear to “grow” on plants during this flow stage, but are not plant parasites and may only harm small plants by covering and shading them.
Slime molds will eventually disappear on their own, but their unsightly appearance begs more rapid removal. A forceful spray of water from a garden hose will wash them away. They can also be raked or turned under in mulch, or lifted using a shovel or garden fork and composted or discarded in trash. When they appear on turfgrasses, they can be mowed.
Despite appearances this slime mold is growing on the mulch beneath this sedum, not on the plant itself. Photo courtesy of Missouri Botanical Garden.
Close-up of fruiting bodies (dark seedlike structures and white stalk) of slime mold on Japanese maple (Acer palmatum). Photo courtesy of Missouri Botanical Garden.
Kemper Center for Home Gardening
Jessika Eidson | Public Information Officer
Many thanks to Garden Horticulturist Justine Kandra and Daria McKelvey, Supervisor, Home Gardening Information and Outreach for the expert information and photos provided.