Q: My blue plums are falling off the tree. What is wrong?
A: Nothing at all. They are falling because they are ripe; having them hit the ground is harmless unless they land on concrete. These are dark blue or purple plums with a white powder on the skin, like that on blueberries. The plums are not bruised when they fall on grass. Apples and several other fruits will bruise and rot after falling, but not these plums. It is even possible to harvest them by shaking the tree and then picking up the fruit.
Your plums, also called Italian plums or prune plums (or Italian prune plums or blue Italian prune plums if you want to cover all the bases) are, as you might guess from the name, of European origin. They are the most cold hardy of the various European plums and the only ones that are dependable in this area. Other plums may crop some years and fail some years.
You can pick prune plums off the tree if they are beginning to soften, or you can let them fall and pick them up. If picked off the tree while unripe, they will continue to ripen in storage, but their full flavor will not develop. Italian plums have a high sugar content, which is why they often are dried to become prunes. Since their natural sugars will ferment, they also can be the raw material for wine and brandy.
For anyone interested in growing a plum tree, nothing could be easier. Although most fruit trees are grown from grafted cuttings, Italian prune plums can be grown from a seed. Save some seeds from ripe fruit and let them spend the winter outdoors. The seeds are among those which will not sprout until they have lived through a winter. Plant the seeds in spring, after their cold stratification, or plant them in the fall and expect them to sprout in spring. I recommend planting several seeds and then selecting the best-looking young tree.
You might even want to start two trees. Plum flowers are self-fertile, so no pollinator tree is required, but they will make a larger crop if cross-pollination happens.
Once the plum tree grows, it continues to be easy to care for. No pests bother it, and it will be naturally disease resistant. When it is old enough to make fruit, usually within five years, it continues to be easy. The fruit does not even need to be thinned.
Q: Are fall asters different from the lavender ones that bloom in June?
A: They are entirely different plants, and fall asters are my favorite season extenders for the late garden. Although there are a handful of aster species, I like the ones bred from northeastern wildflowers, the New York asters (botanically novi-belgii) and the New England asters (novae-angliae). Botanists used to call all of them Aster something-or-other, but then the taxonomists intervened.
Now some asters are officially still asters, but the group has been split into several, with different genus names. You may have to look for information under Symphyotrichon instead of Aster, although some catalogs and online listings still alphabetize the plants as asters. One of these days the taxonomists may come up with a new idea. Meanwhile, the asters will be growing, perhaps smiling to themselves at the complications that people create.
The New England asters are native wildflowers in much of the northeastern United States and southeastern Canada. There even are isolated populations in New Mexico and North Dakota. Since they spread mostly by seed, they have naturalized in many other parts of the world—Europe and Asia, even New Zealand. Unfussy about their surroundings, New England asters thrive in many different habitats. Most of the wildflowers are purple with yellow centers, but the 50 or more cultivars for sale to gardeners have more color variety. They have been wildly popular in European gardens for many years, but not as well appreciated in their native country. Flowers grow at the top of unbranched tall stems, and one disadvantage to their shape is that the lower leaves usually are dead by flowering time. To appreciate New England asters in the flower garden, plant something short in front, to hide the asters’ ugly legs in late summer.
The other variety locally grown is the New York aster. Its botanical name, S. novi-belgii, is for “New Belgium,” a seventeenth century name for the Dutch colony which became New York. Both these asters also are called Michaelmas daisies, since they bloom in the vicinity of St. Michael’s Day, September 29. In western Montana, flowering tends to be a week or two earlier.
New York asters are shorter, and they have a greater variety of colors. There are at least a thousand cultivars in lavender, purple, white, pink, rosy red. All have yellow centers. I am particularly fond of New York asters because they do not display dead leaves, and I love the variety of colors.
Since these asters cannot self-pollinate, they cross continually. In my gardens, the named varieties with which I started are long gone, but the unnamed seedlings which have replaced them are equally charming and healthy.
Both these fall asters are less than fussy about the dirt in which they grow, although they do need good drainage. Occasionally a plant will be infected by powdery mildew. The cure for that is to cut it down. There is every chance that the seedling which replaces the mildew-stricken plant will be disease resistant.
Like other garden perennials, these asters need a moderate amount of irrigation in summer. They also need some direct sun, but they will thrive in part shade. Their flowering time is well into the season of autumn frosts, but the blossoms are unaffected by freezing every night.
Q: Are there any small bulbs to buy for spring besides crocus? I would like some that are smaller than daffodils and tulips. When I have planted crocus, they do not do well.
A: Yes, there are several other bulbs to try. If your crocus have come up sparsely, or have disappeared in a year or two, you can blame predators. Crocus like our climate. However, the bulbs are like chocolate candy if you are a mouse. Most local gardens have a sufficiency of voles, the short-tailed mice which do not hibernate. You can assume that voles have been feasting on your crocus bulbs.
Other small bulbs are less interesting to mice. Look at your favorite nursery, garden supply store, or online for bulbs which grow well here. They include species tulips (early to bloom and short in stature), Iris reticulata (a bulbous iris which blooms as early as crocus), Siberian squill, and Chionodoxa (both small and blue; Chionodoxa occasionally is called glory of the snow). Both these blue flowers spread by seed. They may turn up the next year anywhere that the seeds have blown, and seedlings often bloom in their second year.
If you have a shady spot, try Erythroniums or Fritillarias. You may want to stay away from grape hyacinths (also called Muscari). They can be successful enough to be invasive.
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