When can I plant cannas and dahlias out in the garden?

Since neither cannas nor dahlias are the least bit cold-hardy, planting outdoors for both of these beauties should be postponed until all danger of frost has passed. In order to get a head start on the growing season, you could start the canna’s rhizomes and the dahlia’s tuberous roots in containers that have a growing medium of one part potting soil, one part peat moss, and one part builder’s or horticultural sand. When it is safe to start planting your annuals (in southeastern Michigan that should be right around mid-May), then it will be safe to put your cannas and dahlias in the ground.

What does “heirloom” vegetable mean?

There are many opinions on what is an heirloom vegetable. The most common definition: open-pollinated plants (pollination by wind or insects) which are at least 50 years old, and which have been grown continuously. This would include varieties recently reintroduced by seed companies, but which were previously unavailable through the seed trade. Instead, they were preserved over the years by families, or by ethnic, religious, or tribal groups who handed down the seeds from generation to generation. But it also includes varieties that were commercially available in the 19th and early part of the 20th century. The variety must have a history of its own.

This is a broad definition to many. There are those who consider a variety that was available or is now available commercially not to be a true heirloom. Others dislike the “grown continuously” label because it excludes those that were lost and rediscovered. A good example of a lost variety is the Anasazi bean uncovered by archeologists. It had not been grown for 400 years.

Left out are the “modern heirlooms.” These are the new open-pollinated varieties that are the product of accidental natural crossing or intentional cross-breeding. These natural hybrids have the ability to breed true to type. Many of these will be passed on and fifty years from now will earn the title “an heirloom variety.”

When do you trim a flowering crab tree? Does it bloom every year?

Flowering crabapples are the dominant spring-flowering trees in the northern states. Belonging to the genus Malus, apples and crabapples are deciduous trees with fruits ranging from the size of a pea to apples 2 to 4 inches in diameter. Those with fruits less than 2 inches in diameter are considered crabapples. They are generally small to medium, dense, rounded trees reaching a height of 15 to 25 feet. A few of the varieties have leaves that change color in the fall so they are considered trees with multiple season interest. Most, if not all, new hybrid crabs bloom annually, but older trees may or may not bloom every year.

The best time to prune your trees is in late winter or early spring before the leaves appear as it is much easier to see which branches should be removed and also gives the trees the entire spring and summer to form new growth. However, they can be pruned anytime, and if you want to preserve the total flower show for spring, do it immediately after blooming is complete this spring.

Consider the following reasons to prune before you begin:

1. 1. Prune dead, broken and diseased branches.
2. 2. Correct structural defects. Never allow two equally vigorous leaders to develop on exactly opposite sides of the same trunk. This will be a “weak” crotch, susceptible to splitting as the tree grows older.
3. 3. Cut suckers from the bases of the grafted plant. It takes a little more time, but digging out the suckers is even better. Crabapples are grafted or budded on another kind of root stock. Usually this graft or bud is never more than a foot or so from the ground. All suckers developing below this point should be removed as they will spoil the symmetry and sap the strength of the variety wanted. Left alone, they develop into an entirely different and unwanted plant.

Also remember to:

1. 1. Use clean, sharp tools.
2. 2. Disinfect the blades of your tools after each cut on diseased crabs, or you risk spreading deadly fire blight disease. Isopropyl alcohol works well.
3. 3. When pruning a branch or limb, the key is not too close and not too far from the limb or bud. If pruning a mature branch, be sure to leave the branch collar – the slightly wider part close to the trunk – completely untouched.

As I watered my houseplants this winter, I noticed a powdery white build-up on the sides of both plastic and terra cotta pots. Is this salt? I rarely use fertilizer, and when I do it is something organic, like fish emulsion. I thought salts come from synthetic fertilizers.

Synthetic fertilizers are seldom the only culprits. The best type of water for houseplants is rainwater or melted snow. Distilled water can be used, but the cost may be prohibitive over time as well as the work to carry the jugs into the house. Tap water (well or city) is generally suitable for nearly all houseplants. However, the water should stand overnight in a container to allow the chlorine to evaporate and to reach room temperature.

Whether you live in an area with hard or soft water, both can be harmful to your plants as they contribute to a build-up of excessive salts in the soil. Hard water contains calcium, magnesium and iron salts. Softened water is worse because the softening process exchanges calcium for salts that have no use. Plants use these salts in very small quantities. In large amounts they become toxic. What the plant does not absorb from the watered soil will appear as the white crusty deposits. Repotting in new potting medium will help the already affected plant, and leaching the soil (watering to the point of runoff each time you water, or at least monthly) will help prevent future salt build-ups.

I have Euonymus ‘Sarcoxie’ growing on a chain link fence. Every year, the plant is covered with small bumps and many of the leaves yellow. I think it is scale. I trim out the infested stems, but it seems to come back worse every year. Is there a way to get rid of it without using insecticides or am I fighting an uphill battle? I have a healthy Euonymus ‘Emerald ‘n’ Gold’ nearby. I wonder if I should remove the ‘Sarcoxie’ before it might infect the healthy plant?

The symptoms you describe are the calling card of Unaspis euonymi or euonymus scale. As they feed, these tiny insects cover themselves with nearly microscopic shells that range in shape and color. These well-armored pests are feeding on the undersides of the leaves, causing the yellowish blotches. You are correct to prune out badly infested growth. The gnarly growth habit of euonymus does not easily lend itself to being scrubbed with a soft brush and soapy water, a treatment that works for some scale infestations. Application of dormant oil before plant growth starts in spring may turn the tide, followed up by a summer oil treatment in late June or July when the crawlers emerge (baby scale insects). These oils are not what you really think of as insecticides, the oils merely smother the offending critters. To know when to apply the summer oil use the black electric tape trick. Wrap some black electric tape, sticky side facing outward, around a branch of the plant where you can see scales. When the crawlers hatch they will climb around and stick to the tape looking like whitish dust. Treat with summer oil immediately. Dormant oil and summer oils are different formulations, and used at the wrong time can damage the plants, so read the labels and make an educated choice of products. However, scale in euonymus can be lethal. Because popular varieties of euonymus are readily available at nurseries, you might save yourself a great deal of trouble by removing the ‘Sarcoxie’ before the scale can infect your ‘Emerald ‘n’ Gold.’ Scale, once established, is difficult to eradicate by even the most vigilant gardener. You may prefer to avoid the uphill battle and start fresh!

Several coral bells (Heuchera) in my garden are 1 to 3 years old. On a few of them, the crown of the plant seems to be moving up, out of the ground. Since our last couple of winters have been mild, I wouldn’t think that it is due to frost heave (also, none of my other perennials have heaved). Since the plants now seem to be rather flimsy, should I replant them, lowering the crown to soil level? Did I do something wrong when I initially planted them or is this a characteristic of the plant?

You probably did nothing wrong when you initially planted your coral bells. They are a perennial that ages quickly. It is the characteristic of their crowns to move to the soil surface and to die out in the center of the clump. As a result you see their spindly growth and flimsy appearance. The ones that appear to be heaving are probably the older plants. Heuchera benefits from timely division and replanting every 3 years. In the spring, carefully remove the individual plants, checking the crowns for rot. Also look for small white grubs in the soil under the plants, as well as in the crown. Those are root weevil grubs and they enjoy feasting on the crowns. Cut away any portion that appears unhealthy, leaving a leaf bud or leaves, stem and some root for each division. If root weevil grubs are present, manually clean them from the soil, and rinse the plant roots in water. Rinsing the crown may also dislodge slug eggs, which look like translucent orbs the size of small peppercorns. Slugs have an uncanny ability to leave their eggs in places tightly clustered and evergreen, like the coral bell crowns. Unfortunately, rinsing and squishing the offenders won’t get all the ones who have eluded you in the soil. If at all possible, try to relocate the divisions to a new area. If this is not possible, remove 2 to 3 inches of soil and replace with clean, well-drained soil in the planting area.

Near the side of my home, I would like to plant castor bean from seed next year, but I found out that the plant is poisonous. I don’t have kids, but would it be dangerous for a pet, whether it be mine or a stray?

Although the castor bean plant is quite poisonous, most four-legged animals have more sense than we do, and they instinctively leave it alone. The large colorful seedpods are the most deadly part of the plant. Castor bean loves hot and humid summers, which Michigan often endures. It would probably be best to cut off all seed capsules before they mature, since those pods can shoot their seeds as far as 20 feet away and an animal foraging for something else could mistakenly eat them. Furthermore, some people are allergic to the plant’s sap. It is best to wear protective gloves if you tend to suffer from skin irritations. While castor beans love full sun and are very drought resistant, regular watering insures the healthiest growth and leafing out. You might consider planting bean seeds in a large movable container, but nothing smaller than a half whiskey barrel size. That way you can sow your seeds indoors 6 to 8 weeks before the last frost date, providing warmth and full sun (or bright light) so the seedlings have plenty of room to grow. Next, thin seedlings to only a few, especially if you intend to keep them in the container. If castor bean roots become confined, they stop growing and start blooming. You might search out one of the deep purple leaf varieties for added interest and color.

I am looking for a shrub, other than green, for the front of my house. Preferably, I would like a purple or red color during the spring, summer and fall. I don’t want barberry. Can you recommend anything? What about purpleleaf sand cherry? I need something that doesn’t get too big because it will be at the corner of my house (2 to 3 feet away from the house).

There is a short list of shrubs and small trees that suit your needs. However the first concern before making your selection would be assuring that the plant is properly sited. You mentioned that you would like to plant it 2 to 3 feet from your house. This is generally way too close. The absolute minimum distance from your home should be 3 feet, and if there’s an overhang, even further. Planting too close is not only a hindrance for both home and garden maintenance, but also your home will, because of grading and height, not allow rain to reach the plants roots. That said here is the list. Note that these all will color their best in full sun.

Smokebush (Cotinus coggygria) – 15 by 15 feet. ‘Royal Purple’ and ‘Velvet Cloak’ are two good purple varieties. Smoky, cloud-like panicles of pinkish flowers in June. Smokebush can be kept to a smaller size by hard pruning in early spring, thus sacrificing that season’s bloom. Well-drained soil, full sun.

Purpleleaf sand cherry (Prunus x cistena) – Can grow to 10 feet, but is usually pruned or hedged. A respectable landscape plant when a dark purple, almost black leaf is desired. However, many chewing insects find the leaves just as appealing. Average to well-drained soil, full sun.

Ninebark (Physocarpus opulifolius ‘Diablo’) – ‘Diablo’ has deep burgundy leaves and attractive pinkish-white, button-like blooms in summer. It’s a quick grower to roughly 8 by 8 feet, however it may also be hard pruned in early spring to maintain a desired size. Well-drained site, full sun. It will take some shade but will color best in full sun.

Weigela (Weigela florida ‘Wine and Roses’) – Compact shrub, 4 to 5 feet high and wide. The leaves are a dark burgundy to a brownish purple with bright rose-pink flowers in June, then sporadically through summer. Can be lightly pruned after the June flush to maintain its rounded shape. Average to well-drained soils in full sun.

Redleaf rose (Rosa glauca) – This species rose has bluish to red-mauve foliage (resistant to blackspot), single, bright pink flowers in early summer and clusters of scarlet hips in autumn. This is a vase-shaped rose growing to about 6 feet by 6 feet. Average moisture needs, full sun.

Cutleaf Japanese maple (Acer palmatum var. dissectum) – Very slow-growing, small mounded trees ranging from 2 by 2 feet to 12 by 12 feet (depending on the variety). ’Crimson Queen,’ ‘Garnet,’ ‘Red Dragon’ and many more red-leaved varieties available. Moist, highly organic, well-drained soils in light shade to full sun.

European beech (Fagus sylvatica ‘Purpurea Pendula’) – If there is no overhang. A very slow-growing, weeping, purple, irregularly-shaped tree. Grows to about 10 feet, however can be kept smaller with thoughtful pruning. Moist, well drained soils in full to part sun.

I would like advice on how to lower my soil pH level. I used a home test kit and found my soil pH to be around 7. I have planted lots of evergreen seedlings and would like to lower my soil pH to around 5.5 to 6. Do you have any recommendations?

A home pH test is a good start. It has given an indication that alteration to the soil for optimal health of your plants may be needed. An appropriate next step would be to contact your County MSU Extension office and obtain a soil test kit. Collect the samples and send in the soil for a complete test.

The soil test done by Michigan State University will include much more than just pH. The test results will show the type of soil (clay, loam, or sand) and analysis of the micro and macro nutrients. If, as a part of testing, you tell them what you want to grow, they will make specific recommendations as to the proper type and quantity of material that should be used to amend the soil.

Be sure to evaluate where and how these plants will be situated in the garden. If these evergreen seedlings are to be used as foundation plantings near a house, the soil amendments may need to continue over a more extended period of time than if they are to be planted away from any structure. Also look into how many plants will be contained within how large an area. If this is a small foundation planting, you can simply use a readily available acidifier formulated for evergreens according to package directions.

We would like to interplant lilacs and rose of Sharon as a sight barrier along a property line (extended blooming is the goal of the combination). What are your recommendations? Are the plants compatible?

Lilacs (Syringa) and rose of Sharon (Hibiscus syriacus) have the same site requirements: full sun and fertile, moist and well-drained soil. Both will tolerate light shade. This is an interesting combination as a shrub hedge in the landscape as they are both shrubs that were used in Midwestern “yards” at the turn of the century and have continued to be part of the Midwestern landscape since the earliest communities were built. Both can be formidable shrubs and should be planted away from the house. You may have noticed how they were often planted in the outer corners of rural, then city and later in suburban yards, or as borders, often in front of hurricane fences. They have also been used as foundation plantings but that is not where they show their beauty best.

The height of the lilac ranges from 6 to 18 feet with a spread of 4 to 15 feet, depending upon the cultivars chosen. The rose of Sharon has a height of 8 to 12 feet and a spread of 6 to 10 feet. We welcome spring with the lilac’s profuse and fragrant lavender, pink, or white blossoms in May and June. When they are finished blooming, the foliage is medium to deep green on arching or upright mounded branches.

The rose of Sharon is the other bookend of the spring-summer season, showing off its big, colorful blossoms in the heat of the summer and still blooming when the children go back to school. The big, bold flowers of the rose of Sharon come in white, pink, lavender, violet or blue and can be flat, single blooms to carnation-like doubles to the newer anemone type that has a single flower with a lacy center. During the summer, when not in bloom, the foliage is dark and dense with three distinct lobes.

Both plants have proven that they are hardy, rugged and versatile in the Midwestern landscape. The common lilac is known to have problems with mildew and can become leggy and open at the base, but there are some cultivars such as Syringa meyeri ‘Palibin’ that are less troublesome. Think about throwing an early-blooming forsythia and mid-season bloomer like a spirea into the combination and you will have continuous color.