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Summer Dormancy Is No Mystery

90821thumbCalifornia buckeye, Aesculus californica, is an enigma. How does it survive while defoliated for so much of the year? Not all are so mysterious. Those that live in sheltered or forested situations behave like normal deciduous trees, by defoliating in autumn, and refoliating in spring, after a brief winter dormancy. Those that are more exposed in warm and windy situations make us wonder.

After their brief winter dormancy, exposed California buckeye trees refoliate early in spring, as they should. Then, only a few month later, they defoliate through the warmest and most arid part of summer, which might be a few months long! As the weather cools and the rain starts, they refoliate briefly for autumn, only to defoliate in time for their winter dormancy. They are ‘twice deciduous’.

How do they photosynthesize enough to survive? It seems like they would consume more resources in this process that they could generate. They obviously know what they are doing, since they survive quite nicely in the wild. Furthermore, they are not the only species that can do this. Sycamores sometimes do it if the weather is just so, or if they get infested with anthracnose too severely.

Most deciduous plants defoliate only in winter because that is the worst time to try to photosynthesize. There is less sunlight available while the days are shorter, and the weather is cloudier. Frost, wind and snow would cause much more damage if deciduous plants retained their foliage. Defoliation is how they accommodate the weather. It is no different for plants that defoliate in summer.

Much of California is within chaparral or even desert climates. Native plants, as well as plants that are from similar climates, know how to live here. If they happen to be in a hot and dry situation, some may go dormant until the weather improves, even if they do not go dormant through the mild winters. This is why wild arums and some unwatered acanthus have died back to the ground, and why naked lady amaryllis will remain naked until the first rains in autumn.

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What Bulbs Do After Bloom

90403thumbNarcissus, daffodil, freesia, snowdrop, snowflake, grape hyacinth, various iris and most other early spring blooming bulbs and bulb like plants should be perennials. We plant them with the hope that the will survive after bloom to bloom for another season, and perhaps for many seasons. Some should multiply to provide more bloom over the years. Bloom is just part of their annual cycle.

Lily, crocus, hyacinth, tulip, anemone and ranunculus are not nearly as likely to bloom more than one year for a variety of reasons. Some prefer more chill in winter. Some dislike the long and dry summers. Some survive as perennials, but do not bloom again. However, in some special situations, they also can bloom annually. After spring bulbs, there will be a different set of summer bulbs.

So, what happens after bloom? After exhausting much of their stored resources on production of bloom and foliage, bulbs try to recover and regenerate resources for the following season. Most work to replace their exhausted bulbs with comparable new bulbs. They need foliage to do this, but eventually shed their foliage as their new bulbs go dormant for the following autumn and winter.

Of course, they all do this at different rates. Some smaller bulbs are surprisingly efficient, and shed their foliage as soon as the weather gets warm later in spring. It is amazing that they can store up so much in such a minimal time. Other bulbs shed slowly, as their deteriorating foliage lingers for a few weeks into summer. Foliage of summer bulbs that bloom later is likely to linger until frost.

Because it is essential to the regenerative process, deteriorating foliage can not be cut back prematurely. It is not always easy to hide either. In mixed plantings, it might be obscured by ground cover or other plants. Alternatively, warm season annuals can be planted over the area. Some of us braid daffodil leaves, but others believe that braids draw attention to the deteriorating foliage.

Those of us who still dig and store and perhaps chill marginal bulbs, must wait for complete dormancy.

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Sugaring Season

P90316KThere is no sugaring season here. Spring comes on too suddenly. By the time sap starts to flow, buds are already swelling.

Bigleaf maple, Acer macrophyllum, happens to be native here, although it is not common. It is the sugaring maple of the Pacific Northwest. A tree next to my driveway gave me enough sap to boil about four ounces of maple syrup a few years ago. That was all I needed to make the point to my colleagues who insisted that it could not be done that it really could be done.

Box elder, Acer negundo, is also native, and in riparian zones, is much more common than bigleaf maples is. I am told that is provides sap for sugaring just like any other maple does. Some say the sap is of inferior quality, or boils to cloudy syrup. Others say that it is comparable to that of any other maple.

Now that I made my point about getting a tiny bit of syrup from a bigleaf maple tree, I have no intention of sugaring again. However, sugaring season is still something that I need to be aware of. It is when I can not prune the maple trees. I can prune them earlier in winter or later in summer, but not while they are most vascularly active during sugaring season. Otherwise, they don’t stop bleeding. Even if the bleeding is harmless, it is unsightly if it stains the trunks and becomes infested with sooty mold as the weather warms.

The same rule applies to birch trees.

I pruned a few of the European white birch, Betula pendula, at work last week, believing that it was still too early for them to be too active. It was not much at all, and involved only a few small upper limbs and two significant lower limbs that had been disfigured by pruning for clearance from adjacent utility cables. I did not notice bleeding from the small stubbed limbs that I pruned from high in the canopy with a pole saw. Yet, the sap started to pour from the pruning wounds before I finished cutting away the two larger lower limbs that happened to be on the same tree. They are still bleeding now. In fact, they are bleeding so much that I feel badly that the tree is losing so much sap. If I had known how much sap would bleed, I could have put a bucket under each of the two wounds to catch the sap to make a small bit of syrup as is done in Alaska.

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Plant Bare Root Plants Properly

90206thumbCompared to canned (potted) nursery stock, bare root plants have a few advantages. They are less expensive, easier to handle, more conducive to pruning into a desired form, and they disperse roots and get established more efficiently. One more advantage that is not often considered is that they are easier to install into the garden. For some, it is as simple as poking a stick in the mud.

Perhaps the only disadvantage of bare root plants is that they must be planted immediately, so that they get their roots soaked and settled into the ground into which they will disperse new roots. If planting must be delayed, roots can soak in a bucket of water for only a few days. Unless they are to live in big pots, potting for a season only delays and interferes with efficient root dispersion.

Only bare root trees that need root barriers (to divert roots from pavement) or mesh gopher baskets (to divert gophers from roots) will need planting holes that are as big as those for canned nursery stock. Otherwise, planting holes need be only as wide as the bare roots, and should be no deeper. If soil is loosened too deeply below, new plants will sink as loose soil settles. Graft unions must remain above grade.

Well flared roots can be spread over a cone of soil formed at the bottom of the planting hole. Conversely, cane berries, after their roots get loosened, can simply be dropped into slots formed by sticking a shovel into the ground and prying it back.

Soil amendments that are useful for providing a transition zone between potting media of canned nursery stock the surrounding soil are not so important with bare root stock. Bare root plants only want a bit of soil amendment if the soil is too sandy or too dense with clay. Otherwise, too much amendment can actually inhibit root dispersion by tempting roots to stay where the richest soil is.

Once planted, trees can be pruned as desired. Most come with superfluous stems to provide more options for pruning, and some stems will be damaged in transport. Fertilizer need not be applied until growth resumes in spring.

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Get Perennials Ready For Winter

81212thumbDilemmas are common in gardening. Should summer vegetables that are still producing be removed so that winter vegetables can get started on time? What about replacing summer annuals that are still blooming with winter annuals, and then replacing winter annuals with summer annuals half a year later? Should tender perennials be regarded as annuals, or get a second chance?

Right now, some perennials are looking tired. Many will be going dormant for winter. Many do not get much down time, and will start to develop new growth faster than old growth deteriorates. Not many make their intentions obvious. Deciding how to work with them can be confusing at times. It might take a few years and a few mistakes to get familiar with the habits and lifestyles of some.

If cut back too early, hardy zonal geraniums will not regenerate much until the weather gets warmer at the end of winter. In the interim, they are more likely to be killed by frost without the protection provided by old growth However, some varieties start to grow in winter. If not cut back soon enough, new growth mingles with old, so that they are difficult to separate when they do get cut back.

It is best to observe what hardy geraniums are up to before deciding on when to prune. If they start to develop vigorous new growth down near the ground, the old growth should probably be cut down as far as the new growth. It is likely better to take a chance that they might be damaged by frost. Those that do not start to grow right away can enjoy the insulation of old foliage for a while.

Thoroughly deciduous perennials, like deciduous daylilies, dahlias and some ferns, can be groomed of their deteriorated old growth without risk that they will start to regenerate new growth prematurely. However, cutting back some specie of salvia might actually stimulate development of exposed and frost sensitive new growth. Perennials that get damaged by frost later In winter should not be groomed of damaged growth right away. The damaged material provides a bit of insulation for lower growth, particularly if new growth was stimulated by the damage.

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Take It Slowly In Autumn

81010thumbNo more fertilizer! . . . almost. The main exception is turf that might need a bit of fertilizer if it must stay green through the coldest part of winter, but that is another topic for later. Otherwise, most plants start to go dormant through autumn, and should be as dormant as they get by the middle of winter. Fertilizer later than now could be as logical as espresso just before trying to get to sleep.

Keeping marginally frost sensitive plants up past their bedtime can have serious consequences. Lemon trees are not often damaged by frost in the mild winter weather here. That is because they stop growing through late summer, and the last of their new foliage matures before autumn. Fertilizer applied too late can stimulate late new growth, which is more likely to be damaged by frost.

Plants that like a last application of fertilizer as late as the end of September, such as roses, use it for their last minute preparations for dormancy. It actually takes a bit of effort to abscise (shed) foliage. Besides, healthy foliage is easier to abscise than distressed foliage is. Well fed roots, although significantly subdued by dormancy, work later into winter, and get an earlier start in spring.

Roses are, of course, not as likely to be damaged by late application of fertilizer as lemon trees are. They know better than lemon trees do about what to do when the weather gets cool. They just go dormant. Much of the extra nutrients get ignored as they leach through the soil with winter rain. Many of the nutrients become insoluble and unavailable to plants as winter weather gets cooler.

Autumn is the season for allowing most plants to slow down and get ready for winter dormancy. Trying to get them to be as green and productive as they were in spring can do more harm than good. Only plants that are active through winter, such as cool season vegetables, cool season annuals, and some types of turf, might appreciate moderate applications of fertilizer. If newly installed plants want fertilizer, they should get only enough to keep them happy until they get more next spring.

Posted on by tonytomeo · 26 Comments

Summer Deciduous

P80623K+++That is a term that we do not hear much. There are not many plants that it applies to. Cyclamen is one of the more familiar plants that is summer deciduous. It is from a climate with reasonably mild winters and unpleasantly dry and warm summers. Just like most deciduous plants are dormant through winter to avoid the unpleasantries of the weather, cyclamen defoliates as the weather gets warm in early summer to avoid the expected heat and aridity. It somehow knows how to stay dormant until the weather starts to get cooler in autumn, and is ready to regenerate new foliage and bloom as the rain starts. The active growing season is through autumn, winter and into spring. It is all a matter of taking advantage of the weather while it can, and avoiding the discomforts of severe weather when necessary.

Rhody, like most dogs, has been shedding his fluffier inner winter coat through spring. He still seems to be too fluffy for the weather, but he must know what he is doing. The remaining wiry outer coat provides a bit of shade, and helps to dissipate a bit of warmth when necessary.

Unlike Rhody, I do not have a fluffier undercoat to shed. All that I could do is shed some of the sparse and wiry outer coat. It might have provided shade, but also interfered with cooling air circulation. It does not seem to be designed to dissipate heat like Rhody’s is. Regardless, it was shed just before the Summer Solstice, and will not regenerate until autumn. A barber sheared back the upper evergreen growth first. I then pollarded most of the lower growth, leaving only a pair of formally shorn hedges flanking the upper margin. They too may be removed soon. Antithetically of https://tonytomeo.wordpress.com/2018/01/17/winter-coat/P80623KP80623K+P80623K++

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Bulbs Are Not Finished Yet

41015thumbIt might seem creepy to think about what spring bulbs are doing right now out in the garden. Like victims of a horror movie, they were buried in shallow graves last autumn. They were not dead though. They were undead but merely dormant. While no one can see what they are up to, they disperse roots and begin to push new foliage up to the surface of the soil. Some might bloom soon.

Now it is getting to be time for summer bulbs. Unlike spring bulbs, summer bulbs do not prefer to hang out in the garden through the cool and rainy weather of winter. If planted too early, they can start to grow prematurely, and could potentially get damaged by frost. If planted much too late after winter rain, they will need to be watered more carefully while young, and are likely to bloom late.

Just like spring bulbs, most summer bulbs are really corms, rhizomes, tubers or tuberous roots. Only a few are actual bulbs. Although they are very different physiologically, they perform the same function. They store resources from a previous season through dormancy in order to sustain growth for the next season. Some summer bulbs bloom more than once annually or with many blooms.

Dahlia, canna, crocosmia, hardy orchid (Bletilla) and the old fashioned big white calla are some of the easier to grow summer bulbs. Dahlia is the most colorful, but blooms late in summer or early autumn, and might only perform well for a single summer. With regular watering, canna can grow like a big weed, but in a nice way. The others can grow well enough to get invasive over the years.

Gladiolus and lily will probably bloom for only one summer, but are so colorful that those who enjoy them do not mind. Tuberous begonia is fussier, so is usually grown in pots. Allium, astilbe and maybe liatris have potential to thrive and multiply in the right conditions, but more often bloom for only a few years. Small colored callas are unpredictable too. They are showy but rarely prolific.

After bloom, deteriorating flowers should be pruned away to conserve resources while lingering foliage recharges bulbs for the next winter. This process is known as ‘deadheading’. Gladiolus, lily and any others bulbs that bloom only once obviously need to be deadheaded only once. Dahlia, canna and others that bloom over an extended season will want to be deadheaded a few times.

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Winter Is The Season For Pruning

71213thumbNow that winter is only two weeks away, and many deciduous plants are defoliating and dormant, it may seem as if there will be less work to do in the garden. After all, not much is growing. The funny thing is that this is the best time to sneak up on some of them, and prune them while they are sleeping. Depending on what is in the garden, winter can be just as busy as any other season.

There are a few things that should most certainly not be pruned in winter. Maples and birches should either be pruned before or after winter. They bleed profusely if pruned in winter. Plants that bloom in winter or early spring should be pruned after they have finished blooming. Pruning forsythias, flowering cherries and flowering crabapples earlier will remove much of the blooming stems.

Deciduous fruit trees are of course an exception to that rule. They require annual winter pruning so that they to do not produce too much fruit. Excessive fruit is of inferior quality, and can break limbs. It is acceptable when pruning fruit trees to leave a few unpruned stems to cut and bring in later, as long as they are not forgotten. They can be less refined alternatives to flowering cherries.

Once we determine what should not be pruned in winter, it is easier to see that most deciduous plants should be pruned while bare in winter. Elm, oak, poplar, willow, mulberry, pistache, gingko, crepe myrtle and most popular deciduous trees are sound asleep and unaware of what might happen to them for the next few months. They would be pleased to wake already pruned next spring.

Some evergreen plants should probably be pruned as well. Tristania, redwood, podocarpus, Carolina cherry, bottlebrush and the various eucalypti would prefer to be pruned while the weather is cool. Conifers bleed less this time of year; and pine and cypress are less susceptible to pathogens that are attracted to wounds during warm weather. Avocados and citrus, particularly lemons, should not be pruned in winter, because pruning stimulates new growth which is more sensitive to frost.

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Plant Spring Bulbs In Autumn

71115thumbOf all the gardening chores, planting dormant bulbs is probably the least gratifying. All we do is dig a hole to the required depth and width, set a few unimpressively dormant bulbs with the correct orientation and spacing, and then fill the hole with the same soil that was removed from it. The process gets repeated until all the bulbs are planted. Soil amendment and fertilizer might be added.

There is nothing to show for our efforts. When finished, only bare soil remains. We might want to plants flowering annuals or a light duty ground cover over the bulbs, or we might just spread mulch. If soil amendment is needed, it should be mixed into the soil at the bottom of the planting holes. Fertilizer can get dispersed over the surface of the soil after planting. There really is not much to it.

Planting bulbs is also a chore that is easy to forget about until it is too late. If we do not see them in nurseries, we might not think about daffodil, narcissus, hyacinth, grape hyacinth, freesia, tulip, crocus, lily, anemone, ranunculus, iris or other spring bulbs until we see them blooming next spring. Yet, this is when their dormant bulbs, corms, rhizomes, tubers and tuberous roots get planted.

Many types of bulbs become available in nurseries at the same time, and can be planted as soon as they become available. It might be too early to plant those that are not yet available. Gladiola, dahlia, allium, calla and canna are summer bulbs that will become available later because they likely should get planted later, although calla and canna do not seem to care when they get planted.

Daffodil, narcissus and grape hyacinth are probably the most reliable spring bulbs for naturalizing. Bearded iris is likewise very reliable, but needs to be dug, split and groomed every few years. Freesia and crocus may not naturalize as reliably. Lily, tulip, anemone, ranunculus and hyacinth are spectacular in spring, but are unlikely to naturalize because they prefer more of a chill in winter.

Some bulbs can be phased in their first year. For example, if freesia flowers are expected to last about a week, a second group of bulbs can be planted about a week after the first. A third group can be planted about a week after the second, and so on for a few weeks until the planting season ends. As the first group finishes bloom in spring, the second group begins to bloom, and so on.