Question: When is a golden larch not a Golden larch? The answer is, when it's a Dahurian larch in late autumn. The Dahurian larch (Larix gmelinii) is an uncommon tree, rarely seen in cultivation outside of botanical gardens and arboreta. Native to Asia from Siberia into Mongolia, northeastern China, and North Korea, it is a deciduous conifer that sheds its needles every fall and regrows a new set the following spring.

The exact age of our specimen is unknown, as its planting predates by many decades the era of computerized plant record keeping, prior to which few written records remain. I would estimate it to be greater than 60 years of age. My impression is that it doesn’t seem to be significantly larger than when it first caught my eye in the early 1970’s. Our specimen is singularly noteworthy because larches are so rarely seen in this part of the Midwest. Most species are native to northern regions having cooler and wetter climates. It’s a healthy tree despite a sparse and open habit. It suffered collateral damage in a storm several years ago when falling limbs from a nearby tree broke some lower branches, but nonetheless its vigor remains unchanged.

Not to be confused with its cousin, the Golden larch (Pseudolarix amabilis), which sheds golden needles earlier in October. The Dahurian larch typically retains its needles several weeks longer every fall. In its autumn glory, it can be easily located in the Holly Fields, just south and west of the statue of Mother and Child, standing against an evergreen backdrop of tall American holly trees.

I was feeling a little restless at the office desk the other day and decided the best antidote would be a fast-paced walk around the Garden grounds to refresh my thoughts. To my delight I chanced upon a couple of familiar flowers more typically seen around Mother’s Day, rather than Halloween week.

The first was Rhododendron ‘Soir de Paris’, a deciduous azalea with light pink blooms and a sweet delicate scent growing near the tram shed in the Lopata Azalea and Rhododendron Garden. Its leaves, soon to be shed, bore the scars of a season-long battle with lace bugs, but a handful of flowers were as welcome as an April morning. It’s not unusual to see a scattering of fall flowers on this, and several other cultivars, coming at a time of year when both temperature and day length are within a range similar to when they normally bloom in spring. Individual flowers that open in autumn will not open again the following spring, but those that do will hardly be missed during peak bloom.

Autumn-flowering iris never fail to amaze me, and a large clump of reblooming Iris ‘Theme Master’ in the Goodman Iris Garden did not disappoint. Bending low over the flowers, I drank deeply of their intoxicating scent, then straightened up and headed back to the office with a new perspective on the day.

Due to our location in North America, and the varied mix of our flora, we will always have some fall color. The two questions most frequently asked are how good will it get, and when will it peak? In the great tradition of both weather and color forecasting, I’m hedging my bets, but here’s why:

Addressing the second question first, natural events have been a little behind schedule for much of the growing season, so I wouldn’t be surprised if peak color is also a little late this year – late October, into early-mid November. The abundant, timely rains of spring and early summer had me optimistic for the POTENTIAL of outstanding color. However, the effects of excessive soil moisture, and insect and disease pressures are starting to show up in early browning and premature leaf loss of some trees, especially maples, which normally contribute brilliant colors to the overall mix.

In the aftermath of the unprecedented late-season flood, a cautionary haze has been cast over color predictions for bottomland areas. Unlike spring floods, there is no recent historic experience to draw upon for predicting the outcome of such an event. So I’ll be as interested as everyone else waiting to see what plays out, but I wouldn’t be surprised if the leaves of many of those trees in the recently flooded areas turn brown and die before completing their color cycle.

For trees in drier, upland locations, I still think the possibility of excellent color still exists.

However, as is the case in every year, the final keys to the color puzzle are only played out in the weeks and days immediately prior to leaf drop. An overall pattern dominated by clear, sunny blue skies, followed by cool nights that remain above freezing, can turn a good year into a superb one. If that pattern arrives during the last 2 weeks of September and persists at least through the first 2 weeks of October, then we should have great color. Every day need not fit that template, but most days must.

An overall pattern dominated by warm, overcast and/or rainy weather, especially when accompanied by unseasonably warm nights during that same time frame will produce only average to poor fall color.

Likewise, an early hard freeze that kills the leaves before they’ve had a chance to drop, will also eliminate any chances of extended excellent color.

Keep in mind that Missouri Botanical Garden’s location in St. Louis City, surrounded by cityscapes that produce a “heat island” effect, is therefore slightly warmer than outlying areas. As a result, our trees typically color later in autumn, and among the latest species to change are our many Japanese maples. Their fall color is reliably excellent from year to year and the fact that their foliage is in a healthy condition at this time, bodes well for a great color display on the grounds. So other areas in the region may color first, but the last great show locally is usually found on a stroll around the lake in Seiwa-en, the Japanese Garden. I say mid-November should be ideal this year – provided we don’t have an early hard freeze.

But for all other locations, I’m withholding my final prediction for now. I’ll wait until that gorgeous, clear, crisp day in late November when I’m skipping through knee-high piles of leaves on the ground, reflecting on the weather patterns of the previous weeks, and thinking to myself “Yes, that’s why the color season turned out the way it did….”

The emerald ash borer has recently been found in Wayne County in southeastern Missouri. For now, no additional EAB’s have been found elsewhere in the state. Aptly dubbed the “Green Menace”, the EAB is the greatest exotic invasive threat to American forests since the introductions of Dutch elm disease and chestnut blight. Most likely arriving in North America via wood packing materials in shipping containers from Asia, the EAB was first identified in the Detroit, Michigan and nearby Windsor, Ontario areas in 2002. Since then, it has spread to nine additional states (as of August, 2008) and has been responsible for the death of tens of millions of ash trees. No native ash species are resistant, and the borer attacks all tree sizes from saplings to mature trees. Infested trees typically die within one to three years.

What can homeowners do? Start by learning how to identify the EAB. See identify and identify Their iridescent green color and slender profile are characteristic of the adults, but their small size (approximately one-half inch) makes them easily missed. Understand that there are other iridescent green “look-alike” insects found in Missouri. See look-alikes

First and foremost, maintain the health and vigor of existing trees through timely watering during dry spells, and periodic fertilization. Understand that ash trees are also susceptible to many other insect, disease, and environmental problems. See other problems Minimizing these other problems is key to reducing overall stress. Though studies show that EAB is highly attracted to stressed, open-grown ash trees, unlike other species of boring insects, it readily attacks healthy trees, regardless of location. Don’t plant any new ash trees. Most reputable nurseries no longer sell them. Utilize other tree species and create diverse plantings so your landscape contains no more than 10% of any one single species.

At the present time, no effective means have been found to curtail the spread of this pest. If this trend continues unchecked, it is presumed that all native species of ash will likely be extirpated from North America. In anticipation of this eventuality, Missouri Botanical Garden personnel are joining other conservation agencies in collecting seed of native ash to save germplasm for re-establishing ash trees at some future time. See germplasm

While there are insecticidal products currently available that can protect individual ash trees, these work on a preventative basis only. See insecticides Most are designed to accumulate in the leaf tissue that EAB adults feed on prior to egg laying, but do not control larvae already tunneling inside the tree. No single product or method of treatment has proved to be 100 percent effective against emerald ash borer.

Newer products are currently under study. When they become available, they will likely be for professional use only. Develop a relationship with a qualified tree care company. See arborists and tree services Many firms publish newsletters to keep their customers informed of new developments in the science and industry of tree care.

Decline symptoms in infested trees typically occur in the trees upper canopy first. Epicormic sprouting of new branches from the trunk and lower limbs often accompanies advanced decline. Woodpeckers are highly attracted to EAB larvae tunneling beneath the bark, and unusual activity of woodpeckers in the upper branches of ash trees could be an early warning sign of a developing infestation.

Emerald ash borer has been able to spread at such an alarming rate primarily due to the transportation of firewood from infested areas. Use firewood from local sources only, whether for home use or when camping, and don’t move wood from one location to another unless you’re absolutely certain it’s not ash, or you’re absolutely sure where the wood came from.

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All the young Purple Martins have now fledged from the houses located in the open meadow adjacent to the parking lot west of Monsanto Center. Fledglings hone their flying skills, hunting insects on the wing by day, and return to roost at night in the compartments where they were born. Within a week’s time they will be proficient enough fliers to depart from the nest site and embark on a long and hazardous migratory journey that will eventually terminate in their wintering grounds in southern Brazil and Argentina. As insectivores that feed only on flying insects, Purple martins cannot survive in cold climates where their food source is absent for extended periods.

Next spring, the martins will venture north again to breed in North America, and hopefully many survivors will return, as they do with unerring accuracy, to St. Louis and the very houses on Shaw Avenue where they were born. For information about these fascinating birds, visit the Purple Martin Conservation Association website http://purplemartin.org/

The martin house meadow at the Monsanto Center is next to the plastic pot recycling center at 4500 Shaw Boulevard. Look for them the next time you come by to pitch those pots! http://www.mobot.org/hort/activ/plasticpots.shtml

Photo courtesy of John Miller, Purple Martin volunteer

With apologies to Shakespeare, one old saying leads to another: “Dieback, not tieback” answers the question. Don’t cut off daffodil leaves until they lose their green color and start to turn yellow and dieback of their own accord. Flowering causes bulbs to expend a tremendous amount of stored energy. Healthy leaves are necessary to gather sunlight and convert it into carbohydrates utilized to produce next year’s bloom. This requires a minimum of 6, but preferably a full 8 to 10 weeks after flowering for the bulb to complete its rebuilding process.

For this reason, the widespread practice of braiding the leaves, or bending, folding and securing them with rubber bands to tidy up the garden, is also discouraged. Not only does braiding cut off sunlight to all but the exposed top layer of leaves, but it can also promote fungal diseases, especially during cool, wet weather. Bent and folded leaves are analogous to a bent and blocked straw that can no longer transport liquids efficiently. To insure success in subsequent years, everything possible should be done to encourage and retain healthy leaves until their work is completed. Only after the leaves have yellowed and browned, should they be removed.

Though holly trees (Ilex opaca) are relatively free of serious insect and disease problems, on occasion gardeners may become concerned when yellow leaves occur throughout the canopy. Holly leafminer is a fairly common pest, and in some years damage may be quite conspicuous on older leaves in springtime. For information about holly leafminer, see Holly leafminer.

Extreme winter cold, especially bouts of sub-zero temperatures, can cause yellowing in some years. On rarer occasions any of several leaf-spotting diseases may be the culprit. Their damage is more likely to be cosmetic, rather than life-threatening. More commonly, a lengthy period of drought during the heat of summer can contribute to considerable yellowing and premature loss of leaves. Newly planted hollies are most vulnerable to drought injury, and should be watered weekly in summer and fall.

Iron chlorosis is seen on occasion, and is more likely to occur when hollies are planted in soils with high pH levels. For information about iron chlorosis, see Iron Chlorosis.

By far, the most common cause of yellowing and leaf drop is the loss of older leaves that occurs every spring, just before, and during the development of new growth. So the next time you notice yellow leaves on your holly trees, take a moment to consider the time of year. If it’s springtime, chances are the condition is normal, seasonal and temporary, and no cause for concern.

Note the new leaves in the picture to the left. At this stage of growth, there will always be yellow older leaves being shed.

Azaleas are at peak and they are spectacular this year! They shouldn’t be missed. One of my favorites is My Mary, which is also a Plant of Merit. It’s clear yellow really stand out in the garden.

Our rock gardens are also spectacular – the many cultivars of moss phlox are carpeting the gardens with white, pink, lavender, purple, and bicolors.

The iris garden is also just ready to pop! It too will be spectacular this year. German iris need to be divided every few 2-3 years to do their best. Siberian iris are more forgiving and don’t require dividing as often, usually every 5-6 years or when flowering is reduced.

With widespread frost predicted overnight, newly planted tender bedding plants or warm-season vegetables should be covered to prevent damage. Lightweight materials such as bedsheets or spunbonded horticultural floating row covers will afford several degrees protection. Fasten down the edges so they don’t blow away.

Trees and shrubs can be wrapped in sheets or lightweight tarps overnight.

Bring houseplants and ornamental container plantings indoors into a garage or shed.

Protect individual plants by inverting a large clay pot over them.

For more information see: Protecting Plants from Frost and Late-spring Frost and Freeze Damage to Plants

The peak season of spring bloom has arrived! Crabapples and redbuds are in full bloom. Dogwoods and azaleas will be peaking by the weekend of April 26 and early next week. Tulips, daffodils and pansies add to the display, and are complemented by spring wildflowers and early garden perennials.

Not to be missed is the large drift of Virginia bluebells in the Rhododendron garden. It’s a focal point today, but will be overshadowed soon when the surrounding azaleas cycle into bloom.

Explore the bulb gardens and revel in the stunning display. Come soon! Eighty degree days will make flowers pass by all too quickly. This is your best chance to take notes and names of what bulbs you’ll want to order for your home garden next spring. Extra points go to all of you who discover ‘Fragrant Rose’ daffodil. Take a very deep breath and inhale its perfume. Ah! Just like an old-fashioned rose. You will not believe your nose!

Be sure to check out the voluptuous bathers wading amongst the tulips at the Linnaean pools.

If you’re up to a gorgeous shady walk, hike out to the English Woodland Garden. You’ll see all of the above (sans the tulips) and have the opportunity to experience a virtual sea of Blue-eyed Mary putting on its best show in years.

On your way back, take the long way, following the shoreline of the lake in the Japanese Garden. Drifts of crabapples, azaleas, and Kanzan cherries are taking center stage now.

Not to be upstaged by all the floral glory, half of our resident honey bee colony put on a show of their own Monday afternoon. Off they swarmed – first into a nearby crabapple for a brief stay – then took wing again to points unknown. They’re out there somewhere, and may be visiting the flowers in your garden soon!

It’s not unusual for squirrels to strip bark from trees or shrubs. Though they may do so at any time of year, this is often done in late winter or early spring when natural food reserves are in short supply. The green layer of living cambium tissue located just beneath the bark is highly nutritious and contains sap-conducting vessels that are rich in sugars.

Note the teeth marks scraped into the wood. When stems and branches have been girdled, or stripped of bark all the way around their circumference, all growth from that point outward will die. Partially girdled branches may live, but will be vulnerable to infection and decay. Sprouting may occur from live tissue below the wound, but the symmetry of the original growth will forever be altered.

On your next visit to the Garden you need to include a viewing of our magnificent collection of witch hazels. They take center stage in late winter with Vernal (Ozark), Japanese, Chinese, and hybrid cultivars blooming at this time of year. Their distinctive flowers are a balm for gardeners anxious for the arrival of spring, and the sweet fragrance of many cultivars are a welcome surprise on cold, sunny days.

Older specimens of Vernal witch hazel can be found in the Daylily and Japanese Gardens. Specimens of all types, both large and small can also be found in the English Woodland Garden. Since 2005, our collections have been bolstered considerably with many new plantings, with a heavy emphasis on Hamamelis x intermedia hybrids.

The majority of these can be found in the Jenkins Daylily, Children’s, and Rhododendron Gardens, and in beds on the Knolls adjacent to the daylily plantings. Though most are small specimens, witch hazels often bloom at a young age. Look for them on your next visit, and follow their progress as they grow and mature in the years ahead.