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Invasive Weeds Begin Their Invasion

Some invasive weeds are wildflowers.

Wildflowers may not be what they seem to be. California poppy, various lupines, various sages and several others are native species. Saint John’s wort, periwinkle, mustard and several others are not native. They are exotic but naturalized, so can proliferate as if they are native. In other words, several of the most familiar of wildflowers are invasive weeds.

In fact, some of the most invasive weeds were once more popular for their pretty flowers. These includes Saint John’s wort and periwinkle. Pampas grass, various brooms, yellow flag iris and Hottentot fig are more examples. Mustard likely originated as a home garden vegetable. Many grassy weeds were livestock fodder. Not many weeds were accidental.

Nonetheless, invasive weeds are here and established within local ecosystems now. By their simplest definition, weeds are merely unwanted vegetation. Native brambles qualify as invasive weeds as they invade home gardens. Because they are native, though, they are not invasive in the wild. Most of the most aggressive weeds just happen to be exotic.

Invasive weeds become invasive because of their various unfair advantages. Many lack pathogens that limit their proliferation wherever they are native to. Many lack competition from vegetation that they shared their natural ecosystems with. A few may actually prefer local climate to their natural climates. Weeds exhibit too much variety for generalization.

Although, generally, invasive weeds are accelerating their growth with warming weather. Most are proficient at growing faster than their competition and other preferable species. Several bloom and disperse seed before some deciduous species foliate. Weeds exploit resources before desirable species can. Several rampantly overwhelm their competition.

This is therefore a convenient time for weeding, before invasive weeds grow much more. Their roots will disperse more and be more difficult to pull from drier soil later. With more time, most weeds disperse more seed for subsequent generations. Diligence now might not eliminate all weeds for very long, but it helps. Later, weeds should be less abundant.

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P

This dinky floral spike was all I needed to identify this as white Lathyrus latifolius.

P is for pea, or more specifically, perennial pea, or Lathyrus latifolius, which does not begin with P, but that is not the point. Perennial pea is a naturalized exotic species here. Within our landscapes, it is difficult to kill. I suspect that it is just as difficult to kill outside of the landscapes, although I have not tried. After all, it is quite pretty, and does not seem to be too invasive beyond situations that it finds to be favorable. Trying to kill what grows beyond the landscapes here would be futile anyway, since there is so much more of it beyond the boundaries of what we have access to. However, I would not want to add any to areas where it is not already established and interfering with local ecosystems. That leaves me with a dilemma. I just acquired a perennial pea that I want to grow more of, but there is no place to grow it. Almost all of the perennial pea here blooms obnoxiously bright purplish pink. Very few bloom lighter pink with a swirly pattern. About as few bloom white. I am told that perennial pea can bloom red, but I am getting to suspect that such red is what I consider to be obnoxiously bright purplish pink. Anyway, I found a perennial pea that blooms white a several years ago, and grew several copies of it. I shared all the copies until none were left. I thought that I could always return to the original source for more. Unfortunately, the source was buried under debris that was removed from a mudslide two winters ago. What a bummer! I had been watching for white perennial pea since then. Then, last Wednesday, I saw it! It was not much, since only one floral stalk was beginning to bloom, but it was enough for identification. I got a good bit of its upper taproot and stems for many cuttings. The base of the taproot remains as a more permanent source if I need it, and if nothing happens to it. I am so pleased with this acquisition, even though I have no idea of what to do with it, like so much of what grows out there.

This is a better picture of the original stock from three years ago.

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Some Exotic Annuals Self Sow

Periwinkle can naturalize a bit too aggressively.

It is impossible to say how long native wildflowers have adorned the natural landscape of California. Various lupines, California poppy and evening primrose had always been the most colorful wildflowers locally until they began to be displaced by exotic (non-native) plants only in the past two centuries or so. Although natives are remarkably resilient to dry summers and occasional wildfires, they are not very competitive with more aggressive and prolific invaders. What the natives and exotics have in common though is that they are so well adapted to local environmental conditions that they are able to perpetuate without much help.

Lupines, poppies and evening primrose, as well as native yarrow, godetia, and fleabane, may unfortunately need a bit of help if exotics want to move into their territory. In areas that are regularly or even only sometimes watered, weeding to remove more aggressive exotic plants helps the natives stay in control. They should otherwise do well on their own. Although without irrigation their growing season is much shorter, natives are slower to be displaced, since so many of the otherwise competitive exotics are not adapted to dry summers.

Many exotic flowering annuals are prolific enough to almost become naturalized, but are not quite aggressive or adaptable enough to get very far from cultivated landscapes. Cosmos, nasturtium, alyssum, catchfly (silene), four o’clock, gaura and foxglove self sow so readily that they are considered by some to be invasive. Some of us instead consider them to be ‘reliable’. They can be useful for unrefined parts of the garden that we do not mind watering, but otherwise do not want to put much effort into.

However, foxglove and even nasturtium can actually become noxious weeds in coastal areas not too far from here. I think that forget-me-not, feverfew, baby tears and English daisy can be problematic anywhere that they get enough water. Also, most annuals eventually revert to more genetically stable forms; which is why all varieties of dwarf nasturtium eventually bloom with the same yellow or orange single flowers. Yet, if we can distinguish between the plants that we can appreciate for their reliability and those that can be too invasive, native and exotic wildflowers and not so wild flowers can make gardening a bit easier.

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Mediterranean Climate Is Quite Californian

New Zealand natives perform well here.

“Mediterranean” translates from Latin to “middle of land”. The Mediterranean Sea is in the middle of the land of those who named it. Other regions were either unimportant or unknown to them until the Sixteenth Century. Nowadays, most people of the World are aware of many other regions. A few of such regions also enjoy a Mediterranean climate.

Such climates are obviously not confined to the regions of the Mediterranean Sea. They merely resemble such climates. Some extend eastward into Western Asia. Others are in eastern and southern Africa, southwestern South America and Columbia. Larger regions of such climate are in southern Australia. The closest are here in western North America.

Even these limiting regional designations are debatable. Many horticulturists consider climates of New Zealand to be typical Mediterranean. Such climates are mostly between thirty and forty five degrees north and south. However, some might exist within northern India and southern China. Ultimately, climate is meteorological rather than geographical.

Mediterranean climates receive almost all of their rain during winter. Rain is very minimal through summer. Even if it is twice as abundant in other similar climates, it conforms to a similar schedule. Although winter chill is adequate for many species that need it, frost is mostly minor. Locally, summer weather does not often become too uncomfortably warm.

Native species know what to expect from local climate. So do exotic species from similar climates. Some may prefer more or less winter rain, summer heat or winter chill. Almost all can tolerate warm summers without rain, though. Such weather conditions are normal for them. Therefore, the most adaptable exotic species locally are from similar climates.

This includes species of Eucalyptus, Pittosporum and Callistemon from Australia. Aloe, Agapanthus and Morea are from South Africa. Phormium and Leptospermum are from New Zealand. Oleander and the various species of Lavandula are truly Mediterranean. In the past, a few exotic species adapted too efficiently to become invasively naturalized. Horticulturists are now careful to not import such potentially aggressive species.

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Weeding Season

Weeds pull up relatively easily while the soil is still damp from winter rain.

My garden may lack the sort of ‘riot of color’ that landscapers like to promote to achieve the other popular cliché of a ‘tranquil garden retreat’, but is the victim of a different kind of violence. The desirable plants and undesirable weeds are about as compatible as the terms ‘riot’ and ‘tranquil’ are. Recently, the weeds have been gaining ground in the ongoing battle between the two. In another heroic effort to help the plants that I want in my garden, I will soon venture onto the battlefield to do what I can to defeat the weeds. The native sky lupine, California poppy, California fescue and some sort of native iris would otherwise be displaced by the invading oat grass, oxalis, burclover and sowthistle.

Different weeds invade other areas. Perennial weeds like nutsedge, dandelion, Bermuda grass, bindweed and brambles (blackberry) are among the worst in most areas. Annuals like purslane and spruge can be just as troublesome though. I really dislike the various twining vetches, even though they are good for the soil. Pampas grass, giant reed, blue gum eucalyptus, black acacia and Acacia dealbata are the largest weeds and the most difficult to battle.

All of the weeds that I need to contend with pull out easily while the soil is still damp from winter rains. If I do not pull them now though, they will be difficult to pull as the soil dries. Broom, the nastiest weed in my garden, comes out relatively easily now, but is ridiculously hard to pull from dry soil. Brambles and poison oak also come out easier now like the rest of the weeds, but are of course always difficult to handle.

Sometimes, if I do not have enough time to pull all the weeds in an area, I at least like to keep them from spreading if possible. If I cut annual oat grass down with a weed whacker before it blooms and sets seed, it is unable to reproduce to replace itself before it dies at the end of its season. This also works for sowthistle. Dandelion is perennial, so does not die at the end of its season, but will not spread so aggressively without its flowers or seed.

This has not worked so well with other weeds. Spurge sets seed before I catch it. Yellow oxalis and nutsedge reproduce more profusely by offsets than by seed. Bermuda grass is a creeping perennial that does not mind if it loses its seed. Burclover and bindweed are so low to the ground that pulling them is the only option. Broom and the various weed trees may initially be deprived of their seed, but are harder to pull when they regenerate after getting cut back.

Regardless of what it takes, this is the best time of year to get weeds under control. Later in the season, they will have had time to set seed or get more established. As the soil dries and gets baked by the sun, pulling weeds, or in some cases, digging them, becomes more difficult.

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Weeds Are Prolific And Invasive

Weeds are now growing vigorously everywhere.

Warming spring weather accelerates bloom and growth. Early spring bloom is now much more colorful than the best of winter bloom. Fresh foliage is already replacing defoliated deciduous foliage and faded evergreen foliage. Vegetation will soon be more active than they will be during any other time of year. Such vegetation unfortunately includes weeds.

Weeds are only weeds because they are unwanted. That is their only commonality. Most are exotic, or not native, but a few are native. Most are annuals, but a few are perennials, vines, shrubs or trees. Annuals grow from seed, but several of the others can perpetuate vegetatively. Some are appealing where appropriate, but migrate to where they are not.

Weeds become weeds because they are generally invasive. Many are aggressively so. They grow wherever they can, and compete with any desirable vegetation for resources. The most aggressive annual weeds begin growing before preferable species. They can overwhelm their slower victims. Several have bloomed and are already dispersing seed.

Exotic weeds are here for a variety of reasons. Some arrived inadvertently as seed in fur or digestive systems of livestock. Some were fodder for livestock. Many were originally desirable flowers for home gardens. A few were formerly useful as cover crops or erosion control. Many lack natural pathogens from their native ranges that limit their proliferation.

Regardless of their origins, weeds now necessitate weeding. They grow throughout the year, but most are most active as winter becomes spring. Obviously, they grow like their horticultural designation implies. Those that are not already dispersing seed should not get the opportunity to do so. Less weeding will be necessary later if more happens now.

Besides, weeding is easier while the soil is still evenly damp from winter rain. Roots are more pliable and less dispersed. They toughen and disperse as the season progresses. Rhizomes, stolons and other perennial weed parts are likewise easier to pull or dig now. Tilling might be more efficient for eradication of small but profuse young weed seedlings.

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Poke

Phytolacca americana; pokeweed, pokeberry, pokebush, pokeroot, poke sallet, poke . . . or inkberry

Phytolacca americana is known by several names; pokeweed, pokeberry, pokebush, pokeroot, poke sallet, and simply, poke. I have no idea what poke is, but it is obviously famously associated with this species, which I know instead as inkberry. That is a more sensible name to me, since I made ink from the famously toxic berries. However, within its native range, a species of holly is also known as inkberry.

The ink is initially an obnoxiously bright magenta, but fades to a light brown. Those who prefer the bright magenta color can preserve it somehow. I prefer the faded brown. Because the ink is caustic, it should be used only with disposable quills. Inkberry is also used for dying fabric, either magenta or brown.

Weirdly, inkberry is both extremely poisonous and also edible. Tender young vegetative shoots can be collected as they begin to emerge after winter. They can be boiled and drained a few times to eliminate toxins that might have developed within them by that time. Such growth becomes more toxic as it matures. A few shoots must be left to grow through summer and autumn to sustain tuberous roots below, so that new shoots can grow for the following season. This sustaining growth gets quite large, after providing only a minor volume of edible shoots. In other words, inkberry is a large perennial that needs plenty of space but provides only a small amount of potentially edible but possibly toxic greens. There are plenty of safer and more efficient greens and vegetables to grow in the garden.

Inkberry has become a somewhat invasive exotic species here. We prefer to remove it from public landscapes because its poisonous but pretty berries might be tempting to those who are unfamiliar with it. They certainly look like they would be tasty.

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From the Muddy Banks of the Wishkah

Well, . . . it is not exactly on the muddy banks.

Kurt Cobain was here. So was I. That is how I got this picture of this English holly in this awkward situation within Kurt Cobain Memorial Park, on the muddy banks of the Wishkah River. I wrote about other pictures from there at my other presently discontinued blog, ‘Felton League’, a bit more than a year and a half ago. This particular picture was omitted because it was irrelevant to that particular post. It is more relevant to this horticultural blog.

‘From the Muddy Banks of the Wishkah’ is, incidentally, the second album that the band Nirvana recorded without Kurt Cobain.

English holly is more naturalized on the muddy banks of the Wishkah River and throughout coastal regions of the Pacific Northwest than it is here. There are not many ecosystems that it can not migrate into there. Here, it can infest only ecosystems that retain sufficient moisture through summer to sustain it, such as riparian or coastal ecosystems. Even within such ecosystems, it would not likely survive on top of a piling such as this specimen.

Some of the most prominent vegetation of the coastal ecosystems of the Pacific Northwest is surprisingly similar to vegetation here. Douglas fir, which is sporadically native here, is the most prominent species within the forests there. Bigleaf maple is likewise more common there than here. Naturalized Himalayan blackberry is even more common and more wicked there!

However, to me, the entire region seemed to be riparian. Nothing was far from some sort of waterway. I encountered nothing that resembled a familiar chaparral ecosystem. Someone who is more familiar with the region could distinguish between the various local ecosystems. I should be more observant about the diversity of the ecosystems and their associated vegetation, both native and exotic, when I return late next winter.

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Weeding Before Weeds Start Seeding

Some cultivated species can become weeds.

Weeds are weeds simply because they grow so aggressively where they do not belong. They begin before the weather gets warm enough for desirable plants to grow. Some are already blooming and dispersing seed. This is why weeding is presently very important. Weeds innately compete with desirable vegetation for space, water and other resources.

Weeding should ideally eliminate target weeds before they disperse seed. Some weeds are sneaky. They bloom and disperse seed while young and seemingly innocent. Some conceal their bloom and seed with their lush foliage. They seem to know to do so during rainy weather that discourages weeding. They effectively provide their own replacement.

Some weeds regenerate vegetatively. They grow from stolons, rhizomes, bulbs, corms or other dromant storage structures. Many of these structures were dormant through winter. Some were dormant even longer. They are aware that winter is becoming spring, so now begin to grow. As they do, they generate more of the same structures, perhaps with seed.

Weeding is easiest as soon as weeds are big enough to grip. Their young roots separate easily from their soil before more thorough dispersion. Also, their soil remains thoroughly damp and soft from winter rain. However, it may be easier to eliminate a profusion of tiny seedlings by tilling. Weeding bulkier weeds, such as pampas grass, can involve digging.

Only a few weeds are woody vines, shrubs or trees. More weeds are perennial. The vast majority of weeds are annual. Regardless, the most substantial weeds are woody. Some can regenerate persistently from their stumps. Therefore, weeding of such weeds should involve removal of their entire stumps. It is important to dig rather than cut oak seedlings.

Few native species proliferate undesirably. Therefore, most weeds are exotic. Most were originally desirable, but naturalized. English daisy, periwinkle, pampas grass and broom were formerly popular flowers. Blue gum eucalyptus formerly provided wood pulp. Other weeds formerly grew as vegetables, fruits or grain. Many weeds were once forage crops.

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Exotic Weeds Are The Worst

English daisy gets prolific in lawns.

Exotic species are not native. It is that simple. There is nothing fancy about it. They came from elsewhere to live here. They are not necessarily rare, unusual or innately desirable. Most plant species within most refined landscapes and home gardens are exotic. Native species that inhabit unrefined areas, although trendy, remain unpopular for landscaping.

Not only are exotic plant species not necessary rare or desirable, many are too common or undesirable. With few exceptions, the most aggressively invasive of weeds are exotic. For a variety of reasons, they proliferate faster than native species. Some are aggressive because they are endemic to competitive ecosystems. Most lack natural pathogens here. 

A weed is merely any undesirable plant. Some might be desirable in some situations but not others. English ivy, for example, which is a practical ground cover within landscapes, is also an aggressively invasive weed within coastal forests. Most weeds are annuals or biennials, but others are perennials, shrubbery, vines, aquatic plants or substantial trees. 

An unfortunate reality about exotic weeds is that they are not here by mistake. Generally, their importation was justifiable at the time. Most were ornamental plants for gardens and landscapes. Some came as fruits, vegetables, herbs, cover crops or forage for livestock. Some came as timber. Species that escaped cultivation and naturalized became weeds.

Such weeds compete for the same resources that desirable plants utilize, and are mostly visually unappealing. Some enhance the combustibility of landscapes and forests. A few weeds produce seed structures that are hazardous to pets and wildlife. Even if problems are not directly obvious, weeds disperse seed to share their innate problems elsewhere.

This is typically the best time of year to pull or grub out weeds, although more weeds will grow later. Annual weeds are mature enough to get a good grip on. Soil should be damp enough from winter rain for roots to pull out relatively easily. Weeding will likely require a bit more effort this year because of the extended dry and warm weather since December.