Blue Gum

Juvenile blue gum foliage is very aromatic.

This is the primary eucalyptus that earned a bad reputation for all other eucalyptus. Blue gum, Eucalyptus globulus, arrived in California in the 1850s, and grew on plantations for timber. As its timber proved to be of inferior quality, and demand for wood pulp dwindled, the plantations succumbed to abandonment. Feral trees naturalized into adjacent areas.

Although once a common timber and wood pulp commodity, and effective as windbreaks for agricultural purposes, blue gum was never popular for landscapes. Those that inhabit urban or suburban situations were generally there prior to urban expansion around them. They are far too massive, messy and combustible, and inhibit the growth of other plants.

Mature blue gum trees can be significantly taller than a hundred feet, with elegantly high branched form. Limbs that fall freely from such heights are very dangerous. The aromatic foliage is evergreen. Adult leaves are stereotypically lanceolate and curved. Silvery blue juvenile leaves are blunt, sessile (lacking petioles) and more aromatic than adult foliage. Strips of smooth tan bark shed to reveal paler bark.

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. 

Not all weeds are unwelcome.

Unplanned acacias certainly put on a show when they bloom. It is not easy to dislike something so impressively colorful.

Even the best tended gardens get weeds. Most weeds, particularly annual and perennial weeds, meet a quick demise by getting pulled out or sprayed with herbicide. A few shrub and tree weeds though, are sometimes allowed to mature into functional members of the landscape.

Many sneak into the garden by growing within overgrown or otherwise concealing shrubbery, where they can hide long enough to get established. Others are left to grow because they are recognized as desirable plants. The main problems is that many end up in situations where they eventually become problematic.

Mexican fan palms are distinctive trees. Unfortunately, many grow below utility cables, because that is where birds drop the seed as they eat the fruit. Unlike other trees, palms can not be pruned around utility cables, so must be removed when they get too tall.

Silk tree, black locust, tree of Heaven and various oaks, pines, acacias and eucalypti are some of the more common trees that can sneak into gardens. Sometimes, they happen to land in good situations. More often though, they get too close to foundations, eaves, pavement or other features that they damage as they grow. Like Mexican fan palms, they are easier to remove while young, before they become problematic.

Pittosporums, cotoneasters and privets are commonly seeded shrubbery with less potential for problems. The main problem with glossy privet is that it can be too prolific and aggressive, so that it can crowd out more desirable plants. Most pittosporums and cotoneasters that get seeded are from plants that are ‘straight species’ (not cloned cultivars or varieties). Those that happen to be from cultivar or variety plants will not be ‘true to type’, which means that they will be more like the straight species than like their parents.

The few fruit trees that can sometimes grow from seed have the same problem, since only some of the more genetically basic types may resemble their parents. Fancier types and (non-sterile) hybrids probably will not. Fruit trees that grow from root suckers of grafted trees instead of from seed will be nothing like the parents, and may produce useless fruit.

Pampas grass is a prolific and sometimes welcome perennial weed near untended parcels or forested areas where pampas grass has naturalized. Broom is a shrubby weed that is even more prolific, but never welcome.

Algerian and English ivy rarely grow from seed, but can be really nasty weeds if they get where they are not wanted. Bear’s breech (or breaches), Jupiter’s beard, calla, mint and various yuccas that were planted may be very difficult to eradicate if they are no longer desirable, or if they migrate into areas where they become problematic.

Six on Saturday: Ghost Town

As a result of prioritizing our efforts within the landscapes at facilities that have been in use through summer, landscapes at unused facilities have been neglected. It would be embarrassing if anyone else were here to see the results. Those who maintain the other infrastructure have mentioned that these neglected areas resemble ghost towns. Flowers continue to bloom without any assistance. Also though, weeds continue to grow and toss seed for the next generation. There is so much to catch up on. What is worse is that I will not be working here much until November, and will be gone again in February.

1. While no one is looking, lily of the Nile continues to bloom into the middle of September. I was not here to see it, but I suspect that this particular colony was not blooming on time for July.

2. Kahili ginger is blooming too, but right on schedule. This is obviously a substandard bloom. I am impressed nonetheless. It was not expected to bloom at all. It was just planted over winter.

3. Otherwise, most of the bloom here is that of weeds. Strangely, I do not remember anyone pulling weeds from the pavement before. Could the formerly constant traffic have inhibited them?

4. Should this say “PLEASE LET US GROW ON WALKWAYS” or maybe “PLEASE LET US STAY ON WALKWAYS”? Regardless, I am impressed by the ability of weeds to compose a sentence.

5. Grapes would certainly be easier to reach if they grew on neglected, hanging vines like these. Unfortunately, if left long enough to produce fruit, these vines would become a tangled thicket.

6. Goodness! This is what happens when a ponderosa pine seedling grows under a deck, and no one is here to pull it out before it grows right through! The weed problem here is now serious!!!

This is the link for Six on Saturday, for anyone else who would like to participate:

Online Plant Purchases Have Certain Risks

Many seeds can be found online.

So many plants that were difficult to obtain years ago are now much more available online. The internet does more than give everyone access to nurseries and seed suppliers that sell online. It also makes it possible to communicate with others who might want to share plants and seeds from their own gardens. The advantages are obvious, but there are innate problems with so many plants being too available.

Before humans started to relocate plants all over the world, plants were much more confined to certain regions. Once relocated to new regions, some plants naturalized and became problematic for the plants that were already there. Exotic (non-native) plants often had the advantage because pests that troubled them back home had not come with them.

For example, pampas grass had been confined to the Pampas region of South America. It was imported to California and Oregon because its fluffy flowers and graceful texture are so appealing. The problem now is that it naturalized, and continues to proliferate and crowd out native plants in coastal ecosystems, without natural pathogens to slow it down. The availability of so many more plants from so many more regions seriously increases the potential for the importation of invasive exotic plants, as well as plant diseases and even insects!

Another potential problem is that common names of plants can be very different in different regions. Now, this can be an advantage when seeds from a common yucca in Lubbock, Texas might actually be from the very uncommon plains yucca (Yucca campestris, which I recently purchases on Ebay!). The problem is that the yucca known as ‘Adam’s needle’ in Georgia may be a completely different species from what is known as such in Pennsylvania, Oklahoma or anywhere else. A plant described as a ‘mimosa’ could be a silk tree, a jacaranda tree, or any of several different acacia trees!

Mulch Is Lowly But Practical

Mulch is less interesting than useful.

Gardening is unnatural. Most popular plant species are not naturally native. Cultivars are products of unnatural selection and breeding. Most plants like unnatural watering. Some enjoy unnatural fertilizers. Removal of their detritus is unnatural. So is the replacement of their detritus with mulch. Actually, most of what happens in the garden is quite unnatural. 

Ironically, gardening is how many of us incorporate more nature into our lifestyles. Much of our effort compensates for what plants naturally crave but unnaturally lack. Watering is necessary for plants that get rain through summer within their natural ecosystems. Mulch might be nice for plants that naturally benefit from the decomposition of their own debris.

In nature, most plants benefit from their own debris. They enjoy the nutritiously decaying organic matter and enhanced moisture retention. Their shallow roots enjoy the insulating effect on the surface of the soil. Debris of some plants excludes other competitive plants. Mulch is not a perfect substitute for such detritus, but partly compensates for its removal.

Although it would likely be an asset to the plants that produce it, the detritus produced by most plants can not stay in the garden. Much of it is too abundant. Some is too shabby or too coarsely textured. Some might become combustible as it accumulates. Diseases can overwinter in some types of debris. Mulch is more sanitary, neater and less combustible.

Most mulches are organic matter of one sort or another. Compost does not last long as a mulch, but is appreciated by most plants. Uncomposted chips from a tree service occupy nitrogen as they decompose, but are more effective for inhibiting weed growth. Products that are available as mulch at garden centers are more refined, but also more expensive. 

Some dense ground cover plants perform something like mulches. Many consume more moisture than they retain though. Also, they can retain bits of potentially infectious debris that falls from diseased plants above. Nonetheless, they insulate the surface of their soil, and inhibit or exclude weeds. Gravel over ground cloth is inert, but requires no watering.

Much Ado About Mulch

Not many weeds get through mulch.

Mulch was not invented by humans. Most plants make some sort of mulch naturally. Even desert plants that live on bare ground shed foliage that decomposes to be recycled back into the soil, and provide nutrients for the roots below. Redwood, most pines and most eucalyptus are extreme mulchers that generate thick layers of foliar debris that benefit their own roots, but inhibit the growth of competing trees. Knotweed, Hottentot fig (freeway iceplant), ivy (both Algerian and English) and other dense groundcovers are their own mulch, and also work well for substantial plants that grow amongst them.

There are a few advantages to mulch. Although ground cover mulches consume some degree of moisture, mulches benefit plants by retaining moisture at the surface of the soil. Mulches also insulate the soil, so that it is more comfortable for roots that want to be near the surface. Most weed seeds that get covered by thick mulch can not germinate and emerge through it. Those that try to germinate on top probably can not get their roots through to the soil below. Besides, mulch simply looks better than bare soil.

Mulch is generally spread in early spring, before weed seeds are completely germinated, and while the soil is still damp. However, moisture retention is still a concern through the warm and dry weather of summer. A thin layer of finely textured mulch added over thinning groundcovers (without completely burying the foliage) can rejuvenate tired old stems by giving them something more to root into. This works well for knotweed, English ivy and even trailing gazanias.

Mulches should generally be well composted so that they do not take too many nutrients out of the soil for their own decomposition. However, uncomposted coarse wood chips, like those often recycled from tree services, are even more effective at controlling weeds while fresh, and they tend to decompose before they become a bother to larger plants.

Small volumes of mulch can be purchased in bales at nurseries and garden centers. Composted redwood soil conditioner is a popular soil amendment that can alternatively be a nice finely textured mulch to spread thinly over small areas or in planters. Larger volumes of more coarsely textured and less expensive mulching materials can be obtained by the yard from garden supply stores.

Six on Saturday: Weeds +

Working inside for most of the week has certain disadvantages, especially at this time of year. There is so much blooming that I do not go out to see. I did not get many pictures of camellias or flowering cherries while they bloomed, although some camellias continue to bloom sporadically. Some azaleas are also finished blooming. Rhododendrons are blooming nicely now, but I have not started getting pictures of them. Instead, I got pictures of a few weeds and their associates from just outside of where I work inside.

1. Broom! It is one of the most aggressively invasive exotic weeds of the Santa Cruz Mountains. No one knows if it is Scotch, Spanish or French. It is probably French, but we know it as Scotch.

2. Dandelion infests most lawns. It was probably imported for greens. I will not eat greens that grow in lawns where Rhody does what he goes outside to do. I should move some to the garden.

3. Periwinkle is a naturalized exotic species here, but is not so naturalized farther inland, or in urban areas where lacks space to migrate. I actually planted it where I lived while in high school.

4. Forget me not, as seen in the upper right corner of the previous picture, is naturalized in riparian situations, but is also too delightful to be perceived as a weed. How could anyone dislike it?

5. Pacific Coast iris is not actually a weed. It is not even exotic. This one is a hybrid of a few native species, and was planted intentionally. I would just prefer the ‘unimproved’ Iris douglasiana.

6. Rhody puts the ‘+’ in ‘Weeds +’, which is the title for this week. Perhaps this should have been the first of these six; but then no one would have bothered with the remaining five. Priorities.

This is the link for Six on Saturday, for anyone else who would like to participate:

Wildflowers Are Flowers Gone Wild

Periwinkle is pretty for a weed.

Wildflowers have been quite a fad. Relative to most fads, they are not so impractical. For some situations, they are a good excuse to waste less effort and resources on unrefined parts of the garden. Of course, they all require some degree of effort and resources. Most are neither as wild nor as natural as their marketing suggests them to be. Few are native. 

Wildflowers that lived here centuries ago, prior to the introduction of exotic species, were relatively unimpressive. Although some bloomed spectacularly, they did so within a brief season. Winter is too cool for pollinators that wildflowers intend to attract. Summer is too dry for bloom to last long. Most bloom was limited to the transition from winter into spring. 

The same native wildflowers bloom even less now than they did centuries ago because of competition with exotic species. Most exotic species that compete with wildflowers are feral forage crops that lack colorful bloom. They grow so vigorously that they obscure the natives. Mitigation of such undesirable vegetation ruins wildflowers that mature within it.

Most of the best wildflowers here now are as exotic as feral forage crops. Those that are native might be more reliant on unnatural cultivation. California poppy, evening primrose, and native annual lupines might prolong bloom with a bit of extra water through summer, but need weeding. With the same watering, (non-native) cosmos stands up to the weeds. 

Unfortunately, vegetation management is more important than wildflowers outside of the refined garden. Overgrown weeds are combustible and can be dangerous to pets. Weed whacking too often involves wildflowers before they get their chance to bloom, as well as foliage of spring bulbs after bloom. (It sometimes damages bark of trees and shrubs too.)

Some low and dense perennial wildflowers are more reliable than annual sorts because they exclude annual weeds. Saint John’s wort and periwinkle are invasive exotic plants, but work well as ground covers. Mowing or shearing them late in winter slows their competing weeds, and also enhances their foliar density before competing weeds regenerate.

Lawn Weeds Are Low Down

Lawns require significant maintenance and weeding.

Weeds are constantly a problem here. There is no season in which every sort of weed is inactive. As some annual types finish dispersing seed and die off for winter, others begin their season. Most weeds just happen to be most active as winter becomes spring. They try to stay ahead of desirable plants. Lawn weeds have been proliferating faster than turf. 

Annual weeds were easiest to pull while still dispersing roots, and while the soil was still damp from winter rain. Biennial weeds that grew last year are more firmly rooted, even if their soil is damp. Perennial weeds are most persistent, with extensively dispersed roots. Of course, as lawn weeds, all three types are more challenging than in the open ground.

Separation of weeds from turf grass is significantly more work than pulling weeds alone. It is not so easy to reach down into the roots of the weeds. Nor is it so easy to pull weeds without pulling some of the turf grass with them. The process is likely to leave bald spots. Many of the persistent perennial lawn weeds are more firmly rooted than the turf grass is. 

Dandelion is notorious for leaving bits of root behind when pulled. These bits regenerate into new plants that are even more difficult to pull than the originals. The various species of oxalis persist by various means. Some produce bulbs or offsets that are impossible to separate from the soil. Others develop thick networks of sinewy stolons that break apart.

Some persistent lawn weeds, such as plantain and English daisy, as well as many of the feral grasses, are so difficult to eradicate that they ultimately integrate into the lawns that they infest. It is simply easier to mow over them than to try to eliminate them. They never quite assimilate though, so interfere with the uniformity of color and texture of their lawns. 

Unfortunately, some lawn weeds do worse than merely compromise the visual appeal of turf. Burclover and foxtail can be dangerous to pets. Their seed is designed to stick to fur. Burclover seed structures can tangle and accumulate in long fur, causing dense matting. Foxtail seed structures can lodge into eyes, nostrils, throats and ears, or pierce soft skin.