Q: I really like the yellow flowers and purple-blue berries that I've seen on mahonias furthur north in California. Are there native ones I could grow here?
A: Yes, there are quite a few species and hybrids, from ones that grow 10 ft tall to ground covers, that will do well in our area. One of the best is Mahonia "Golden Abundance", a hybrid developed years ago at the California Botanic Garden. This one grows upright to 8 ft tall and can be planted 4 ft apart to use as a hedge. The prickly, dark-green, holly-like leaves make a good barrier. Birds love the berries. Plant in full sun (although it will tolerate some shade it will flower less), water the first year to get established, and after that it does fine with regular or little or even no water. For a really prickly, grayish-leaved native with translucent red berries, you might consider Mahonia nevinii. It is endangered in the wild but available in nurseries. Mahonia repens does fine in light shade and is a good choice for a ground cover.
Q: My melons are ripening but some are showing signs of rot on the bottom. What can I do?
A: This is pretty common and there are several ways to prevent it: 1) train the vines up so the fruit is off the soil (you might have to put the melons in a sling to hold their weight), 2) put a piece of wood, a stone or something else under the fruit to keep it off the ground, 3) build a ridge of soil around the place where the stem emerges from the soil, about a foot or two out, and confine water to that area, 4) punch holes in several coffee cans, sink them in the soil in the root zone and use them to deliver water to the roots. These methods work for vining squashes as well.
Q: I planted an Arbutus 'marina' as a drought-tolerant tree. Will it need summer water and what can I do for the aphids it has developed?
A: Where Arbutus 'marina' evolved is unclear but it is thought to have Mediterranean heritage. It does best with regular (but not necessarily weekly, every two to four weeks should do depending on time of year and rainfall), moderate watering throughout the year and as with almost all trees, it's good to make sure that water reaches down at least 2 feet so that all the roots have access to it. If watering is shallow, the deeper roots can die and the plant will suffer. And of course, the water should cover the area from about six inches from the trunk to the outer tips of the branches. For the aphids, have you tried blasting them off with a strong jet of water? Encouraging aphid-eating insects and birds might also help with this.
Q: My family loves corn so we planted some this year. How will we know when to harvest the ears?
A: When the silks turn brown, the ears are close to being ready. Peel back the husk on an ear and puncture one of the kernels about two inches down. If the liquid is watery, the ear isn't ripe; if the liquid is gooey, you waited too long for perfection (but it will still be great in corn chowder or cornbread); if the liquid is milky, the ear is ready for eating! At this point, speed is of the essence: the sugars in corn kernels start to turn to starch as soon as you pick the ear, so for the sweetest corn, minimize the time from vegetable plot to cooking pot.
Q: My camellias bloomed profusely this year but the plants are getting a bit rangy and hanging too far down over the sidewalk. When can I prune them?
A: Camelliias generally flower quite well without any pruning but they can get a bit leggy as you have discovered, especially if they are in too much shade. Soon after flowering is the best time to cut them back a bit, so now is a good time to prune. (Camellias are dormant when in bloom and start into new growth after that). Cutting off the terminal buds will stimulate the growth of branches below them. You can actually cut off most of the previous year's growth to encourage a bushier plant. Pruning can be done in summer or early fall as well, and unwanted shoots can be removed anytime.
Q: Is double-digging a good idea?
A: "Double-digging", the practice of removing topsoil ( the first dig), loosening the subsoil and digging in soil amemdments (the second dig), and replacing the topsoil, used to be very common, especially for vegetable gardens. The modern consesus is that it is generally not a good idea because it tends to disrupt the natural layering and organisms in the soil, it's too easy to mix the topsoil and subsoil, it can lead to greater erosion, and it can release stored carbon into the air. It's also a lot of work! However, if the soil is badly compacted in the only sunny area you have for a kitchen garden, and you do this carefully, it can be a help, especially if you mulch the soil afterwards. For most beds, and even for vegetable ones, just adding compost regularly for the soil critters to pull down and the roots to use, gently aerating the soil with a garden fork, and watering regularly (making sure not to push out the air by walking on the wet soil) should keep most beds (and your back) in decent shape. And of course, raised beds are always an option.
Q: I'd like to create a flowering hedge and I love hibiscus. Would that work?
A: Yes, tropical hibiscus (Hibiscus rosa-sinensis) does well in frost-free areas in full sun (may need a bit of shade in very hot areas) and can be pruned into a lovely evergreen hedge, but it takes a bit more work than other plants. Hibiscus is a fast grower and blooms on new wood so if you don't prune, you will get fewer and fewer flowers. However, an overall pruning will slice up a lot of the large leaves, so if you decide to use the electric hedge clippers, consider doing one side each year which will encourage blooming but let new leaves have time to grow. A second method is more work but the hedge will always look good and bloom well. In June target about a third of the branches, evenly distributed throughout the shrub, and cut them back one or two feet into the shub. In July, do this to another third of the branches, and in August do the last third. This way you will keep them in bounds and have lots of flowers too. Note: the fancier varieties of hibiscus don't tend to make as dense a hedge, and giant white fly can be a problem.
Q: Most of the lemons on my tree look quite ordinary but a few of them are shaped really oddly with pointy bits. What has caused this and should I worry?
A: It sounds like the fruit is showing damage due to citrus bud mites. These suck sap from bits of the ovaries of the flowers as they develop. Odd-looking but not hazardous to your health or to the tree's. If there is a large problem, you could try treating the tree in June and October with one of the sprays based on vegetable oil. This should kill most of the bud mites but avoid killing the helpful predatory mites on the tree. However, if there are only a few of these peculiar lemons, I'd just leave the tree alone. (Note: there will be a photo of an affected lemon in the February newsletter.)
Q: I'd like to keep the poinsettias I bought to decorate the house. Any advice about doing that?
A: So, keep inside, plant outside, or toss? Poinsettias (Euphorbia pulcherrima) are frost tender, prefer acid soil, grow to 8 ft in the ground, and do not bloom well unless they get two months of pretty much total darkness at night in the fall. With care you can provide this indoors and keep them going for quite a while, but they do tend to drop the green leaves and start looking leggy. Darkness is hard to provide in an urban garden, so unless you enjoy a challenge, this is not going to be successful. However, I have seen some blooming in the occasional garden around here so no reason not to give it a try. If you do keep them growing, wear gloves when pruning as the milky sap of euphorbias can cause skin irritation. (By the way, poinsettias are not poisonous–that’s an urban legend.)
Q: I've noticed that a lot of tree trimming is going on at the moment. We have a large coast live oak that could do with a bit of care. Is now the right time to do that?
A: Live oaks should be pruned in the summer when their growth slows. Winter or spring pruning can cause them to produce "witch's brooms", wispy growth at the branch ends that are the result of a fungal infection. When you do prune, all the cuts should be made back to where the branch starts, as stubs may not heal and are likely to die back and cause rot problems.
Q: I planted some of our native yarrow (Achillea millifolium) several years ago. It has done well and slowly spread, but lately the center seems to be dying, although the outer bits seem just fine. What is wrong?
A: Actually, it's pretty certain that nothing is wrong, fortunately. Plants, like people, have a limited number of days on earth--since the plants in the center are the oldest parts they are most likely just reaching the end of their life. All you need to do is cut the stems down to about 6" tall and dig up the clump. Then remove the dead center and toss it in the compost, divide the healthy outer portions and replant them to start new clumps. Now is the perfect time to do this.
Q: I know we don't get enough natural outside chill for hyacinths, tulips or Dutch crocuses, but I'd like to plant some anyway. What do I need to do?
A: You are right that these need a cold period in order to bloom so put them in brown paper bags (not plastic) in a part of the refrigerator where they will be cold (but not frozen) for 6-8 weeks. Be aware that too much ethylene gas, which is given off by ripening apples (and bananas and pineapple), can cause the bulbs to rot or sprout prematurely, so keep these fruit in airtight bags. You can also sometimes buy prechilled bulbs and just plant them directly. Also, unlike the classic Dutch tulips, some natural species tulips do fine without a chill, and so do saffron crocus which bloom later (and you get to harvest the saffron!). You might also consider opting for some of the Tazetta narcissus varieties which tolerate our climate quite well--I have some paperwhites that have bloomed dependably for the last 20 years.
Q: I'd like to replace some of my Bermuda grass lawn with raised beds. How can I get rid of the grass?
A: Each bit of the Bermuda stolons or rhizomes left in the soil, as well as any seeds, can grow and once you irrigate your beds, they are very likely to do so and come up in the vegetables. Digging up all the area and sifting the soil is labor-intensive (I've done this so I know!) and you are still likely to miss some pieces. I personally avoid herbicides so you might consider solarization of the areas where the beds will go and for at least 2 feet around the perimeters of the beds to kill as much as possible of the Bermuda. Now is a good time as we will have hot weather for the next few weeks and solarizing takes 4-6 weeks. Remove the grass or mow it short (put the refuse in the trash). Water the area as that makes the heat penetrate better, and then right away put down a layer of clear UV resistant polyethylene over the area--1.5-4 mils plastic drop cloths are an option--weighing down the edges. There are likely to be bits of Bermuda lower in the soil that don't get killed, but most of the seed and the bits in the top few inches should be. After the solarization, be sure not to cultivate the soil or you may bring up bits and seeds that didn't get killed. The other alternative is just to resign yourself to continually removing the Bermuda as soon as it appears in your beds. If you are vigilant, eventually you should defeat it but it is likely to take quite a while (no method is instant). Landscape fabric covered with mulch around the beds will help control invasion from the edges.
Q: Now that we've been spending so much time indoors, I've increased my collection of houseplants which is great for my mental health. However, some have developed unsightly brown tips and edges to the leaves. How can I prevent this?
A: There are a lot of reasons this might happen: overwatering, underwatering, low humidity, drafts, too much fertilizer, high salt concentration in your tap water or a combination of some of these. First of all, find out what the preferred growing conditions for the plant are so you can narrow down the possible culprit(s). Then change one of the factors and see if the plant improves. If not, try the next possibility. Sometimes it's a hard slog to figure this out.
Q: I've been pruning the exuberant new growth on some of my shrubs to keep them in bounds and noticed that some of the new growth on my variegated ones is completely green. What should I do?
A: As soon as you see these, prune them out down to the place where they start. Green shoots are more vigorous than the ones with the variegated leaves--the plant will favor them and eventually you will have an all-green plant if you ignore them.