This column addresses the role of humidity and ventilation, proper feeding and pest control. For more advice, consult the University of California’s California Garden Web site (http://cagardenweb.ucanr.edu/Houseplants/), gardening books at a local library, or the staff at nurseries with a large houseplant selection. Consider investing in a comprehensive indoor gardening guide to help you learn about the plants in your care.
Most houseplants are native to tropical areas, where conditions are warm and humid. To increase the humidity easily, place pebble trays under houseplant containers. As the moisture around the pebbles evaporates, relative humidity increases. Grouping plants also helps a bit. Surprisingly, misting the leaves does not affect humidity much, although I find that some tropical plants with large leaves seem to benefit.Other plants will rot if spritzed with water, so be sure you understand each plant’s needs.
When feeding houseplants, follow package directions to the letter. More is not better.Excess fertilizer can kill a plant.
Houseplants need nitrogen (N), phosphorus (P) and potassium (K) as well as very small amounts of other minerals, called micronutrients. Most fertilizers contain a blend of nutrients in varying proportions. Foliage plants need more nitrogen, while flowering plants need more phosphorus.
Fertilizers come in several forms, from liquid to granules to sticks. Although roots take up the most nutrients, leaves can also absorb them. However, ordinary fertilizers will scorch foliage, so be sure to select a foliar fertilizer if you intend to treat the leaves.
Common houseplant pests include aphids, fungus gnats and spider mites. There are many types of aphids, and they can increase at an alarming rate. They feed by sucking plant sap. Infestations typically appear on soft, young growing shoots and around flower buds. If you catch them early,you can vanquish aphids by pinching off affected shoots or gently washing off the aphids with tepid water. You can also spray aphids with insecticidal soap, which smothers them. After spraying, wipe them away.
Fungus gnats are tiny, dark gray flies that flit about on top of the soil. The larvae feed on rotting vegetation in the soil. Plants growing in severely infested soil appear weak, grow poorly and often lose older leaves.
To combat fungus gnats, allow the soil to dry out between each watering. Use sticky yellow traps to catch adults. Alternatively, repot the plant in fresh soil. If these measures fail and the plant is large and worth saving, you can drench the soil with Bacillus thuringiensis(Bt),a safe and effective organic pesticide.
Spider mites are probably the most dreaded houseplant pest. They pierce the leaves and suck out plant juices.They hide on the underside of leaves and may go unnoticed until the plant is seriously infected. Affected leaves may show numerous yellow pinpricks, or they may be dry and limp although still green. If uncontrolled, spider mites can kill one plant and then move on to others.
Dry conditions encourage spider mites. Keep plants humid by placing them on beds of pebbles. If only some parts of the plant are infested, clip off those parts and dispose of them in a sealed plastic bag. Treat the remainder of the plant with insecticidal soap at least twice at five-day intervals. Pesticides often do not provide controlas spider mites rapidly become resistant to them.
In an upcoming column, I’ll discuss common houseplant diseases, soil needs, repotting and propagation. In the meantime, bring your houseplant questions to the Napa County Master Gardener Help Desk (address and hours below).
Workshop: Join Napa County Master Gardeners for a workshop on “Rose Pruning” on Saturday, January 18, from 10 a.m. to noon, at the University of California Cooperative Extension (address below). January is the best time to prune your roses. Come learn pruning techniques from a certified rosarian. Bring your rose questions. Online registration (credit card only)
Mail-in registration (cash or check only).
Napa County Master Gardeners welcome the public to visit their demonstration garden at Connolly Ranch on Thursdays, from 11:00 a.m. until 1 p.m., except the last Thursday of the month. Connolly Ranch is at 3141 Browns Valley Road at Thompson Avenue in Napa. Enter on Thompson Avenue.
Master Gardeners are volunteers who help the University of California reach the gardening public with home gardening information. Napa County Master Gardeners ( http://ucanr.org/ucmgnapa/) are available to answer gardening questions in person or by phone, Monday, Wednesday and Friday, 9 a.m. to Noon, at the U. C. Cooperative Extension office, 1710 Soscol Avenue, Suite 4, Napa, 707-253-4143, or from outside City of Napa toll-free at 877-279-3065. Or e-mail your garden questions by following the guidelines on our web site. Click on Napa, then on Have Garden Questions? Find us on Facebook under UC Master Gardeners of Napa County.
Many gardeners have the same questions about caring for indoor plants. Why do the tips of the leaves turn brown? What’s the right amount of water? Why doesn’t my plant bloom? What’s that stuff on top of the soil, or crusted around the pot? Can I grow succulents indoors?
Indoor gardeners face many of the same issues as outdoor gardeners. They must choose their houseplants wisely and understand each plant’s requirements for light, water, temperature, humidity, soil and fertilizer. What’s more, indoor gardeners have to be actively involved in plant care.
Palms and spider plants, for example, benefit from bright light and even some direct sun. Succulents and cacti require fast-draining soil and infrequent watering, while the umbrella plant needs frequent watering to thrive indoors. Orchids placed in the sun will scorch. African violets prefer filtered light and even some fluorescent light in winter. The active indoor gardener takes time to learn about each plant’s ideal growing conditions.
The staff at local nurseries should be able to advise you about the houseplants you select. You may also want to purchase a comprehensive indoor-gardening guide to read more about the plants in your care. The University of California’s California Garden Web site (http://cagardenweb.ucanr.edu/houseplants/) can answer many questions.
Houseplants need light to manufacture their food through photosynthesis. Most foliage houseplants are evergreen and native to tropical or subtropical climates. In their natural habitat, they typically live under a canopy of taller vegetation, receiving plenty of indirect bright light but no full sun. In our homes, however, walls and roofs diminish the amount of light and create dark corners with little bright light.
In addition, the angle of light changes seasonally. Some areas of your home may experience direct light in winter, while summer’s sun is too high to enter the room. The amount of light in a room can vary dramatically. Take time to study the available light in your home and notice how it changes over time. Light duration, intensity and quality all have an impact on indoor plants.
As for water, plants need it for many chemical processes. They take it up by their roots and distribute it via a network of water-conducting tissues. Alas, water—too little or too much—contributes to many plant problems. The houseplant novice has the same question as the outdoor gardener: How often should I water my plants?
Two key rules govern houseplant watering: Never permit the soil to dry out completely, and never allow plants to stand in water for an extended time. Roots may die in either situation. As a general rule, a plant in a pot six inches or less in diameter needs water when the top inch of soil is dry. For plants in larger pots, wait to water until the top two inches are dry. Use your index finger to check for moisture. If the soil feels damp, do not water.
Ordinary tap water is usually fine for indoor plants. However, if your water is artificially softened, do not use it on houseplants.
Brown leaf tips may be an indication of inconsistent watering. Use a calendar or other reminder to track your watering schedule. Cacti and succulents do not need water as frequently as umbrella plants. Watering every houseplant every Saturday earns you points for consistency but may not be a good practice.
Providing a comfortable temperature is also essential to your houseplants’ health. Most indoor plants tolerate normal indoor temperature fluctuations. Foliage plants grow best between 70°F and 80°F during the day and between 60°F and 68°F at night. Indoor flowering plants, such as bulbs, miniature cyclamen, African violet and primrose, prefer the same daytime temperatures as foliage plants but lower nighttime temperatures, 55°F to 60°F. These lower evening temperatures promote recovery from moisture loss, intensify flower color and prolong flower life.
Avoid exposing houseplants to wide temperature fluctuations or to extremely high or low temperatures. These conditions may cause plant decline, evidenced by a spindly appearance, damaged foliage or flower drop. Be an active indoor gardener and move plants from windowsills and doorways when the temperature spikes or plummets.
In future columns, we’ll explore other houseplant requirements—for humidity and ventilation, fertilizer, soil, repotting, propagation and pest control. In the meantime, bring your houseplant questions or concerns to the Napa County Master Gardener help desk (address and hours below), or e-mail us your questions using the diagnosis form on our website.
Napa County Master Gardeners welcome the public to visit their demonstration garden at Connolly Ranch on Thursday mornings, from 10:30 a.m. until noon, except the last Thursday of the month. Connolly Ranch is at 3141 Browns Valley Road at Thompson Avenue in Napa. Enter on Thompson Avenue.
Master Gardeners are volunteers who help the University of California reach the gardening public with home gardening information. Napa County Master Gardeners ( http://ucanr.org/ucmgnapa/) are available to answer gardening questions in person or by phone, Monday, Wednesday and Friday, 9 a.m. to Noon, at the U. C. Cooperative Extension office, 1710 Soscol Avenue, Suite 4, Napa, 707-253-4143, or from outside City of Napa toll-free at 877-279-3065. Or e-mail your garden questions by following the guidelines on our web site. Click on Napa, then on Have Garden Questions? Find us on Facebook under UC Master Gardeners of Napa County.
Keep a record of what you planted, noting which varieties you loved and which choices did not turn out the way you had hoped. In my garden this year, my most productive bed was a large trellis of ‘Roma’ beans, with a different-colored cherry tomato growing up on both sides.
Both beans and tomatoes were abundant producers this year, but the best part was the bounty of basil, carrots and lettuces I harvested from seed that I broadcast at the base of the beans. The beans created a shady shelter and a cool little microclimate that kept me in crisp lettuce, baby carrots and leafy basil all summer. I will definitely try to recreate that setup next summer, although I will do so in a new spot.
The main tomato I planted from seed this year was an Italian paste variety. The plants were easy to grow and prolific, but the taste was bland and lacked the acid I like. To their credit, the tomatoes were heavy, cooked up well, and were easy to slice neatly. Still, I am going to try a different paste tomato next summer.
I also grew a squash called ‘Serpente di Sicilia,’ a fun plant to grow for the three-foot-long zucchini-like vegetable. Its striking, pure white blossoms looked like hibiscus flowers. Alas, my rabbits liked the squash more than I did. I have to think about that one some more.
If you have enough space to move crops around, sketch a map of your garden so you can rotate crops and avoid soil-borne diseases. If your space is limited, consider using more trellises and other structures to grow crops up rather than out.
Stop watering trees and shrubs now. They need to go dormant. Spend the extra time choosing and preparing sites for any bare-root trees, shrubs, vines and roses you want to add to your garden. If possible, prepare planting holes before the steady rains begin and the soil becomes too wet to work. Do continue to water newly planted evergreens and perennials as needed.
If you did not get bulbs in the ground or in pots in October, it’s not too late. Nurseries, garden centers and catalogs still have a great selection. Narcissus and tulips are beautiful in pots and urns as well as in beds. Also consider grape hyacinth (Muscari) and other larger hyacinth.
If you crave color in winter and spring, sow seeds of wildflowers, alyssum, sweet peas and love-in-a-mist (Nigella damascena). Transplant primroses, snapdragons, hollyhocks, pansies, stock and carnations. Poppy seeds and seedlings can go in the ground now, too.
Many of us still have harvesting to do. Pomegranates and persimmons are almost ready to pick, and guavas and olives are ripe, too. Pumpkins and winter squash have reached harvest size, and radishes, carrots, spinach, lettuces and other greens are enjoying the cooler weather. Tomatoes are mostly finished for the year, although a bed cover such as Reemay can keep some plants producing a little longer.
If you keep a year-round vegetable garden or want to, now is the time to sow seeds of carrots, radishes, spinach and lettuce. Garlic, shallots, asparagus crowns and artichokes are also available now at nurseries.
In areas that receive more than 20 inches of rain per year, University of California Extension recommends treating fruit trees with a dormant copper spray to control fungal diseases. Read label directions and follow them precisely. Good coverage is more important than the strength of the mixture so take the time to spray from all angles.
Remove dead limbs from your orchard trees and haul them to the dump or chip them for compost. Clean your tools with a 10 percent bleach solution when you are finished to avoid transferring any problems to healthy plants.
Clean up the garden to eliminate hiding places for slugs and other pests that can make your spring-planted seedlings disappear overnight. If you are still raking up leaves, consider saving some in plastic bags so you have “browns” for your spring compost pile. Make sure they are dry before storing them.
November is a busy month, with chores ranging from tidying up to planting violas and snapdragons for winter color. Next month the list won’t be quite so long.
Open garden: Napa County Master Gardeners welcome the public to visit their demonstration garden at Connolly Ranch on Thursday mornings, from 10:30 a.m. until noon, except the last Thursday of the month. Connolly Ranch is at 3141 Browns Valley Road at Thompson Avenue in Napa. Enter on Thompson Avenue.
Workshop: Join Napa County Master Gardeners for a workshop on “Indoor Gardening” on Saturday, November 9, from 9:30 a.m. to 11:30 a.m. Transform a room into a vibrant living space with houseplants. Learn how to use color, texture and pattern for design and how to care for houseplants. The workshop will be held at the Senior Multi-Use Center, 2185 Elliott Drive, American Canyon. Online registration (credit card only) Mail in registration (cash or check).
Master Gardeners are volunteers who help the University of California reach the gardening public with home gardening information. Napa County Master Gardeners ( http://ucanr.org/ucmgnapa/) are available to answer gardening questions in person or by phone, Monday, Wednesday and Friday, 9 a.m. to Noon, at the U. C. Cooperative Extension office, 1710 Soscol Avenue, Suite 4, Napa, 707-253-4143, or from outside City of Napa toll-free at 877-279-3065. Or e-mail your garden questions by following the guidelines on our web site. Click on Napa, then on Have Garden Questions? Find us on Facebook under UC Master Gardeners of Napa County.
