Grapefruit

Grapefruit originated as an unlikely hybrid.

Citrus have been in cultivation for centuries. Most breeding and selection was intentional. Even the strange breeding of orange and lemon for the familiar ‘Meyer’ lemon was deliberate. Grapefruit, Citrus X paradisi, is a peculiar one though. Its parents were unknown when it mysteriously appeared in Barbados in about 1750. It is now known to be a hybrid of orange and pomelo, both exotic.

The original grapefruits were ‘white’ grapefruits, with tart and pale yellowish flesh. ‘Pink’ grapefruits, with milder flavor, and blushed flesh, appeared a century and a half later, in about 1906. Those with rich pink flesh are known as ‘red’ grapefruits. Some mildly flavored modern white grapefruits are hybrids of grapefruit and pomelo. Such breeding makes them 75% pomelo and 25% orange.

Both modern and traditional white grapefruit trees are more vigorous than pink and red grapefruit trees. Dwarf white grapefruit trees grow slowly, but might eventually get more than fifteen feet tall. Standard trees can get as big as shade trees. They are too productive for home gardens. Pink and red grapefruit trees rarely get taller than eight feet. Grapefruit foliage is evergreen and lustrous.

Citrus Fruits Ripen Through Winter

Mandarin oranges are at their best.

Winter seems like an odd time for fruit to ripen. Winter weather is cool enough to inhibit vascular activity in plants. That is why most plants are dormant to some extent through winter. Most familiar fruit trees are deciduous, so defoliate in winter chill. Stone fruits ripened through early summer. Pome fruits ripened through late summer and autumn. Nonetheless, citrus fruits are now in season.

The various citrus fruits and their cultivars ripen at various times through their season. Like stone fruits and pome fruits, they are on distinct schedules. Furthermore, climate affects ripening. Citrus fruits that ripen earlier than other cultivars in a particular climate may ripen after the same other cultivars in another climate. A few cultivars produce sporadically, or notably later than citrus season.

Such cultivars are justifiably popular. For example, ‘Eureka’ lemon is a mutant of ‘Lisbon’ lemon. ‘Lisbon’ lemon works well for orchards because all the fruit ripens within a limited season. ‘Eureka’ is more practical for home gardens because it instead produces sporadically throughout the year. A few fresh lemons are always available. The winter crop is abundant, but not too overwhelming.

Mandarin oranges are the first citrus fruits to harvest, even if they are not the first to completely ripen. Because their rinds fit so loosely, they are the most perishable of citrus fruits. They will oxidize and dehydrate before they rot. Tangerines are the same, since they are merely American descendants of Mandarin oranges. ‘Rangpur’ lime is not a lime at all, but a sour Mandarin orange hybrid.

Oranges, lemons and grapefruits, although ripening now, can remain on their trees for quite a while. The tartness of grapefruits mellows with age, and might be preferable after a few months. The same applies to the acidity of lemons. However, too many lingering citrus fruits can inhibit bloom. Some limes are supposedly best before totally ripe. All citrus fruits stop ripening when harvested. Juice of the various citrus fruits can be frozen for storage if necessary.

‘Eureka’ Lemon

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‘Lisbon’ lemon actually came first. It is still grown in orchards for lemon juice and other lemon products. The glossy evergreen foliage is a nice bright green. The late winter bloom is nicely fragrant. Mature trees can be kept about twelve feet tall, or allowed to get much taller. Besides the nasty thorns, the only other problem is that all the fruit ripens within a limited season.

‘Eureka’ lemon, Citrus limon ‘Eureka’, is a mutation of ‘Lisbon’ that is more casual about its schedule. It produces a good quantity of fruit in season through the end of winter, and also produces lesser quantities throughout the year. Because it is so productive, the lesser quantities should be more than sufficient whenever lemons are needed.

The ‘Variegated Pink’ lemon is a mutation of ‘Eureka’, so is a mutation of a mutation. The foliage is nicely variegated with white. The green fruit is striped with yellow until it ripens to yellow. The pulp and juice are pink of course. Like many variegated plants, the ‘Variegated Pink’ lemon stays much smaller than ‘Eureka’ lemon, and is more sensitive to frost.

No One Likes A Sucker

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Citrus have been bred for centuries.

Citrus trees that are grown from seed take a few years to mature enough to produce fruit. As they mature, the juvenile stems are outfitted with thorns that are even nastier than thorns on adult growth! Because most citrus has been extensively bred, seed grown trees are very likely to exhibit genetic variations. This is why citrus trees are cloned from stems of stock trees.

Cloned trees are genetically identical to their parents, so will always produce the same fruit. They are cloned from adult growth, so do not need time to mature from juvenile seedlings. They can therefore bloom and produce fruit as soon as their roots are ready. Also, their thorns are less dangerous.

Cloning citrus is not as simple as rooting them from cuttings though. With few exceptions, citrus trees are grafted onto genetically different rootstock. Most citrus trees in home gardens are grafted onto dwarfing rootstock that limits the size of the trees when mature. Orchard trees are grafted onto rootstock that allows them to get significantly larger.

The graft union, where the upper part of a grafted tree is attached to the rootstock, is typically visible just above the ground. The base of the trunk below the graft union is typically a bit more stout than the relatively lean section of trunk above the graft. Trunks of old trees are often more furrowed below the graft union than above it.

Sometimes, the rootstock tries to do more than provide roots. It can produce stems from below the graft union, known as ‘suckers’ that can potentially compete with the grafted portion of the tree above. Unfortunately, understock grows more aggressively than most types of citrus, so can overwhelm and shade out the desirable parts of an otherwise healthy citrus tree.

The most common understock for citrus produces suckers that are outfitted with unusually big and wicked thorns that are not to be messed with! If fruit develops, it seems to be humongous and disfigured lemons that lack flavor. Before they overtake good citrus trees, suckers should be pruned neatly away as they develop, without leaving any stubble to regenerate more sucker.

Orange

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Not all oranges are this orange.

Most of us know what oranges are. The color is, of course, orange. They are very juicy and sweet. Cultivars that are most popular for eating fresh, particularly ‘navel’ oranges, are easy to peel and separate into segments. Those that are best for juicing, such as ‘Valencia’, are a bit smaller with thinner rind, so are a bit sloppier to peel and separate. Such ‘sweet’ oranges are Citrus sinensis.

Richly tangy blood oranges are of the same species, but have blushed or deep red pulp and juice. ‘Sanguinelli’, although rare here, is nonetheless the most popular of the blood oranges, and is a traditional citrus component of sangria. The juicy fruit is compact, with tightly fitting thin skin, comparable to that of ‘Valencia’. Rarer ‘Moro’ produces plumper fruit that is easy to peel and eat fresh.

Sour and bitter oranges, which are very rare here, are mostly Citrus auranticum. Sour oranges, such as ‘Seville’, are used for marmalades and confections. Bitter oranges are used for flavorings and fragrances, such as ‘Bergamot’ for Earl Grey tea. Both bitter and sour oranges were less rare a century ago, when some were appreciated for alluringly fragrant bloom and handsome foliage.

Citrus Are Summery Winter Fruits

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Kumquats are now at their prime.

Citrus seem like such summery fruits. Chilled lemonade and lemon meringue pie are best during warm weather. There are certainly plenty of lemons that ripen randomly throughout the year, and plenty that last for months on their trees. Most limes, some grapefruits and ‘Valencia’ oranges will be around in summer too. Otherwise, most citrus are at their best right about now, through winter.

Mandarin oranges are traditional ingredients of well stuffed Christmas stockings. Where winters are cold and snowy, far from where they grow, they seem contrary to their natural ripening season.

Of all the citrus, they are the most perishable, so are best as they ripen. Their loosely fitting skins, that are so easy to peel, allow them to oxidize and dehydrate more readily than other citrus fruits.

Tangerines are just Mandarin oranges that were developed in North or South America. ‘Rangpur’ limes are actually sour Mandarin oranges that are somewhat less perishable because their skins happen to fit more firmly. Calamondins, which are odd but likely natural hybrids of Mandarin oranges and kumquats, are diminutive tangy fruits that do not last much longer than Mandarin oranges.

‘Bearss’ limes are preferably harvested right as they grow to mature size, but just before they ripen completely. Their flavor mellows as they ripen and yellow. Fortunately, they develop sporadically through an extensive season, so can be available any time fresh limes are desired. Grapefruits can be left intentionally to mellow on their trees after ripening, although this tactic can inhibit bloom.

Otherwise, many citrus fruits can last for more than three months on their trees without consequence. Some improve with mellowing. ‘Meyer’ lemons, which are a hybrid of an orange and a lemon, ripen like richly flavored lemons, and then mellow like very tart oranges. Since citrus fruits stop ripening when harvested, it is advisable to taste one before harvesting too many that are not ready.

Some ripened Mandarin oranges may have slight green blotches. ‘Valencia’ oranges may be slightly yellowish.

Autumn Simply Will Not Wait

40917thumbReady or not, it will be autumn in just a few days. Formal hedges can be shorn one last time if they need it. They will not grow much until spring. Actually, photinia and the various pittosporums should not be shorn much later than now if they exhibit any dieback. Some of the diseases that cause dieback are more likely to infest freshly cut stems during rainy weather. Citrus and plants that can be sensitive to frost should not be pruned later, since pruning can stimulate new growth that will be more sensitive.

For the same reason, most plants should not need fertilizer as their growth naturally slows. Through winter, new growth is likely to be damaged by wind or discolored by nutrient deficiency. Even if the nutrients that keep foliage green prior to autumn are in the soil, some are less soluble at cooler temperatures. It is really best to allow plants to get some rest. Only plants that are active through winter, like cool season vegetables, cool season annuals, and some cool season turf, will benefit from fertilizer.

However, some plants that are generally dormant through cool winter weather will not be completely inactive. Many plants, particularly tough evergreen perennials like lily-of-the-Nile, African iris and many ferns, continue to disperse their roots to be ready to sustain new foliar growth next spring. This is one of the reasons why autumn is the best time to get such plants into the garden, even if they do not seem to do much until spring. Autumn is also a good time to seed lawns or install sod.

The other reason for planting in autumn is that, as the weather gets cooler and rainy, new plants that have not yet dispersed their roots will be less likely to dry out than they would be in spring or summer. Some bulbs that will soon be available in nurseries want to be in the garden before winter because a bit of cold weather promotes healthier bloom.

Citrus On The Sucker List

90501thumbA five pound kumquat is a problem! It means something went seriously wrong. Anyone who grew one would concur. They are huge, lumpy, and very insipid, with ridiculously thick pale yellow rind around a small handful of uselessly fibrous pulp. They are protected by dangerously sharp and rigid thorns that can get longer than three inches. Even their irregularly wavy foliage is unappealing.

In reality though, there is no such thing as a five pound kumquat. These huge but useless fruits, as well as the associated thorns and foliage, are those of ‘shaddock’, which is the most common ‘understock’ for almost all grafted dwarf citrus trees. It is what keeps such trees compact, so that they do not get as big as orchard trees. It was there all along, whether we were aware of it or not.

Most citrus trees are composed of two genetically different parts. The understock are the lower parts that develop roots that are unseen underground. The desirable upper parts that produce the familiar citrus fruits grow from ‘scions’ that are grafted onto the understock. Graft unions are just above grade, where the texture of the bark above is slightly different from that of the bark below.

‘Suckers’ are stems that grow from the understock below the graft unions. Because they are genetically identical to the understock rather than the scions, they produce the same fruit and exhibit the same physical characteristics as the understock would if it were growing wild. Suckers can overwhelm desirable scion growth, which is how kumquat trees can produce huge five pound fruits.

Other grafted trees and shrubs, particularly fruit trees, get suckers too. New suckers appear as new spring growth develops. They should be peeled off of the main trunks rather than pruned off. As brutal as this seems, it is more efficient than pruning. Soft young shoots should snap off quite readily. This technique removes more of the callus growth at the bases of the suckers, which could develop more suckers later. Big older suckers should be pruned off as closely and neatly as possible.

Lisbon Lemon

90417It may not be the mother of all lemons, but Lisbon lemon, Citrus limon ‘Lisbon’, is the original cultivar from which ‘Eureka’ lemon was derived; and ‘Variegated Pink’ lemon was later derived from ‘Eureka’ lemon. ‘Variegated Pink’ is still uncommon, and the pink juice is unusual, but because its variegated foliage is less efficient than greener foliage, it is more manageable in small spaces.

The only distinguishable difference between ‘Lisbon’ and ‘Eureka’ is the scheduling of the fruit. Both are the biggest of the dwarf citrus, and can get as tall as second story eaves. Both have nicely aromatic glossy green foliage. Both are somewhat thorny, and get big thorns on vigorous growth. Yet ‘Lisbon’ is now rare, while ‘Eureka’ is second in popularity only to the unrelated ‘Meyer’ lemon.

That is because, after primary winter production, ‘Eureka’ continues to produce sporadically throughout the year, which is what most of us want in our home garden. ‘Lisbon’ may seem to be more productive, but only because it produces all of its fruit within a limited season that is finishing up about now. The fruit that ripens now may linger for months, but no new fruit ripens until next season.

Citrus And Avocado From Seed

71227Is it possible to grow citrus from seed? The quick and simple answer to that question is, “Yes.” After all, many cultivars of citrus were originally bred from other cultivars, and then grown from seed. But of course, this an overly simplified answer to an unrealistically simple question about a surprisingly complicated process. Perhaps a better question is “Should citrus be grown from seed?”.

Almost all citrus are grafted for a variety of reasons. Those that are not grafted are grown from cuttings only because they do not need whatever advantages understock (or rootstock) provides for their counterparts. Either way, they are all cloned by some form of vegetative propagation. This ensures that they are all genetically identical to their parents, without potential for genetic variation.

Citrus have been bred and developed so extensively that most types are very genetically variable. Those that are the most variable tend to produce fewer seeds, and might even be classified as seedless. Those with more seeds are probably more genetically stable. Nonetheless, it is impossible to predict if seed grown citrus will resemble their parents, or be something totally different.

Furthermore, citrus are cloned from ‘adult’ growth that is ready to bloom and develop fruit. Those grown from seed start out with vegetative ‘juvenile’ growth that will not bloom. Juvenile growth is typically more vigorous and thornier than adult growth, and possibly wickedly thorny! Some types of citrus outgrow their juvenile phase quite readily, while others may take several years to do so.

Avocado trees grown from seed exhibit some of the same difficulties. Although they lack thorns, they do grow very vigorously and very tall for quite a few years before they bloom. By the time they develop fruit, the fruit could be too high to reach, and quite different from the original.

Just because citrus and avocados can be grown from seed does not mean that they should be. However, different is not necessarily bad. Many seed grown avocado trees get pruned into