Crossing borders with houseplants

I live in Seattle, but am going to Canada for an extended stay. Can I bring my houseplants across the border?

Generally, Canada allows houseplants from the mainland United States, but you may be asked to provide proof of origin at the border. The Canadian government page on guidelines for visitors and seasonal residents spells out the details. Here is an excerpt:
“Houseplants are defined as plants commonly known and recognized as such, which are grown or intended to be grown indoors. Bonsai plants are not considered to be houseplants. If you are importing houseplants from the continental United States as part of your baggage or household effects, you do not need phytosanitary certificates or import permits. For all other plants from the United States, you may require a phytosanitary certificate from the U.S. Department of Agriculture and an import permit from the CFIA.”

Spacing and growing butternut squash and raspberry

We’ve bought some butternut squash starts, and from what I’ve read online,
they require a lot of space. This will be my first time growing them. We
have 4′ x 6′ x 1′ raised beds, and I’m wondering if one bed will be big enough to plant 1 butternut squash start. Also, I’ve read that they require staking?
Is this true? What should we do with the other 2 starts that we got if we don’t have room for them in our raised beds? Try planting them directly into
the ground? I’d hate to throw them out…

We also bought a raspberry plant, and I’ve read that they should have 14-18″
for their roots. Again, our raised beds are only 1 foot deep. Would we be
better off digging a hole in the ground?

There is conflicting information in different sources about the amount of space butternut squash needs. Most sources say (as Seattle Tilth’s Maritime Northwest Garden Guide does) the gardener should allow 18-24 inches between plants, which would mean you could plant all 6 starts in one 4′ by 6′ raised bed. Steve Solomon, however, says in Growing Vegetables West of the Cascades that winter squashes require much more space, so that you could only plant two in your 4′ by 6′ bed.

Staking winter squash can be done to save space. There is a pretty good description of how to do it in Mel Bartholomew’s book, Square Foot Gardening. Basically, the vines are planted 4 feet apart in a trench prepared with “large-mesh wire fencing” on 6-foot posts, and twined through the fencing as they grow. He says the stems are strong enough to support the heavy squashes. The technique is also mentioned in Vegetables, Herbs & Fruit: An Illustrated Encyclopedia by Matthew Biggs, Jekka McVicar, and Bob Flowerdew.

As for your raspberry, it will grow faster and better with deep, rich soil. However, raspberries have a tendency to spread by underground runners, so it is often a good idea to contain them in some way. Depending on what is under your raised beds (i.e., soil, sand, concrete) you may wish to plant them there despite the shallow depth, or dig/mound up within the raised bed to improve the soil depth, or plant the raspberry elsewhere.

Chipped laurel as mulch

I have a laurel hedge that I am taking down. Can I use the chips as
mulch or will the mulch kill things as I’ve heard that laurel is
poisonous?

Is your laurel an English laurel? If so, it is the plant Prunus laurocerasus which does have toxic properties (cyanogenic glycoside and amygdalin, according to the information here from North Carolina State University Extension) but I think that the toxicity mainly affects people and other creatures if they eat its leaves, twigs or seeds. My guess is that the wood chips should be safe to use, but what you could do is use the mulch on a path or other area where you do not want plants to grow and it will not touch anything you will eat.

University of Georgia School of Forest Resources has a list of potentially allelopathic tree species and Prunus laurocerasus is not among them.

Ideal time to plant tree peonies

I was given a tree peony in a container. It even has a couple of buds.

Can I plant it in the ground in spring, or must I wait until fall? How should I prepare the soil for planting?

Expert opinions vary on the importance of waiting until fall
to plant tree peonies, or Paeonia suffruticosa. The Sunset
Western Garden Book (2007) says “All peonies are best
set out in fall”, while The Gardener’s Guide to
Growing Peonies suggests that if peonies are planted
in spring, the gardener must be very careful to water
them well in dry weather that first summer. Of course,
watering will still be an issue if your gift remains in
the pot all summer! Also, this same source says in an excerpt:

Tree peonies usually become available in the early
spring and…have small flowers. While it is very
tempting to allow the plants to flower, this can
considerably weaken a young tree peony. The buds are,
therefore, best removed…and the shoot pruned to leave
three or four leaves… Tree peonies are normally
sold…in pots…with a peat-based compost. This is a
suitable medium for transport, but the plants can
deteriorate if they are not planted out fairly quickly
into normal soil. … In the autumn, it can be dug
up…and planted correctly in its permanent home.

I don’t know about you, but I wouldn’t be willing to
nip off those little buds! The “heeling in” practice, which
involves planting the peony temporarily, might work though.
Organic Gardening magazine published an article on this
subject, from which you can read an excerpt:

To heel them in, choose a sheltered, shady site and dig a V-shaped
trench. Make the trench wide and deep enough to accommodate the plants’
roots and long enough to prevent crowding. Place the plants in the trench
at an angle, making sure the roots are below ground level. Refill the
trench with soil (don’t pack it down) and water the plants thoroughly.
Check the soil moisture occasionally and water as needed. “You can leave
plants heeled in for months, but I would suggest holding them that way
only for a few weeks,” says Amy Grotta, extension faculty in forestry
education at Washington State University. “You don’t want them to break
dormancy before planting.” Plants that come out of dormancy early are
susceptible to frost damage, so plant as soon as possible to prevent
harming your new purchases.

Directions for preparing the soil are very consistent
in different literature: your tree peony will need a
sunny site with rich soil, and “Tree peonies benefit
from the application of a heavy layer of
compost–particularly if they are grown in sandy soil”
(says Martin Page in The Gardener’s Guide to Growing
Peonies). At least several days before planting, you
should dig a hole at least one foot in diameter, and up
to 3 feet in diameter, and amend the soil as needed in
that planting hole. Unlike herbaceous peonies, tree
peonies are planted 6 inches deep (that is, with the
graft union 6 inches deep).

Pruning Daphnes

I have some very healthy daphne bushes full of
blooms and I am wondering if and how I should deadhead them…
or do some judicious pruning now that their
flowering season is about over. I live on Whidbey Island,
Washington. The plants are two years old and doing very well
where they are planted.

The standard advice with Daphnes is that they are
usually best left unpruned. If you need to keep them compact,
you may be able to do a little light pruning. Peter McHoy,
author of Pruning: A Practical Guide (Abbeville Press, 1993)
says that no Daphne species needs routine pruning, but it is
a good idea to remove straggly shoots in early spring. If you
do prune hard, it will be a year before flowering returns to
normal. Writing in the New York Times, August 3, 2006,
Leslie Land asks John Bieber of the Daphne Society about how to prune
if you must: “Choose a dry morning shortly after spring bloom is over. Sharpen the
shears. Cut back lightly; severe pruning is always a gamble. It is
safer to take two or three springs to downsize a badly overgrown plant.”

Another resource, with a description of the grab-and-snip pruning technique
for mounding shrubs may be found in Cass Turnbull’s The Complete
Guide to Landscape Design, Renovation and Maintenance (2006).
Although she advises against pruning Daphnes unless it’s absolutely necessary,
this technique can be used in spring. Cut off or cut back to a side branch and
branch that is lying on the ground or extending into places where you do not
want it to go. You can also remove some of the longest branches that are lying on top of other branches.

I would err on the side of conservatism, as Daphnes can be
temperamental. Since yours are doing so well, I suggest that
you only remove the bare minimum of leggy limbs, if you decide to prune.

Prunus species in the Seattle area

I would like to know how well the following trees will do in the Seattle area ?

(1)Prunus mume var. ‘Matsubara Red’

(2)Prunus ‘Kiku-shidare-zakura’

Both species you mention should do well in the Seattle area. Prunus ‘Kiku-shidare-zakura’ is described in Arthur Lee Jacobson’s Trees of Seattle (2006). Its other common name is ‘Cheal’s Weeping Cherry.’ The Japanese name means “weeping chrysanthemum cherry.” Its form is arching and weeping from the point where it has been top-grafted. According to Jacobson, the tree tends to be gawky and a bit sparse, but the flowers are very double. It is common in Seattle.

Prunus mume is also listed in Jacobson’s book. This tree and its cultivars (such as ‘Matsubara Red’) are less common in Seattle. You might be able to see examples in the Seattle Japanese Garden, the Kubota Garden, or Seattle Chinese Garden.

Because the common name of Prunus mume is Japanese apricot, there is sometimes confusion between Japanese flowering cherries and apricots. Prunus mume does produce fruit, but they are small and “bland to somewhat bitter,” and in Japanese cuisine they are preserved in salt and used as a condiment (Umeboshi plum). The more familiar fruiting apricot tree is actually Prunus armeniaca (and its cultivars).

Plants that repel mosquitoes

Is there really a plant that will ward off mosquitoes, and if so, what is the name and is it available in the Seattle area?

There is disagreement about the extent to which certain plants repel mosquitoes. Below, please find some web sites that highlight some plants that may work.

There are eleven plants generally thought to repel mosquitoes:

Citronella, Eucalyptus, Pennyroyal, Rosemary, Rue, and Wormwood. Milder ones (in our experience) include Basil, Bay, Lavender, Sage and Thyme. With even the smallest of herb gardens, or access to a supermarket selling freshly-cut herbs, the leaves of such plants can simply be rubbed on pets and people to temporarily ward off insect attacks.
(Source: Janette Grainger & Connie Moore. Natural Insect Repellents for Pets, People & Plants. 1991, p.11.)

According to Donald Lewis of the Department of Entomology at Iowa State University, citrosa, lemon thyme or citronella grass may help repel mosquitoes, but you have to crush the leaves and rub them on your skin to make them work.

According to the MadSci Network, citronella oil may be more effective at repelling mosquitoes than the plant itself.

Lastly, Colorado State Cooperative Extension recommends scented geranium, lemon grass and a host of other plants.

There are many local nurseries which may carry the plants mentioned above, but since inventory changes frequently and they do not list their inventory online, it is best to give them a call to find out if plants you are seeking are available.

Because of the ongoing concern about West Nile Virus, there is a lot of information available on ways to control mosquitoes. See King County Public Health’s resources on this topic.

Propagating trumpet vine

I have a trumpet vine. I needed to move it, and during the relocating, I also cut its woody upright trunk about 3 feet up, and it was about 6 feet — the woody part. It had a lot of leaves, or branching growth. I wonder what would I have to do to start a new plant from this part I’ve cut off?

The best way to propagate the top part of your vine Campsis radicans) is with semi-ripe or hardwood cuttings.

North Carolina State University Extension has good general information on propagation. The Royal Horticultural Society’s page about Campsis includes information on various propagation methods.

Hibiscus plant care and pruning

How do we prune a Hibiscus tree that is about 3 feet tall? The plants are located in a container outside of our senior center. They wintered inside and are now too bushy at the top. How do we prune so they are more compact? What is the correct way to care for these wonderful flowering trees?

It sounds like you have Hibiscus rosa-sinensis—the tropical evergreen shrub. Late spring is the time to prune. According to the American Horticultural Society Pruning & Training book: Prune established plants by cutting back main shoots by as much as one-third, and shorten laterals, leaving two or three buds. Dead wood attracts canker, so it should be removed promptly. To renovate completely, remove older branches entirely and cut the remainder back hard. The response is usually good, but if most stems have died back, it is best to replace the plant.

(Source: American Horticultural Society Pruning & Training, ed. by C. Brickell, 1996, p. 201).

Other pruning information is available from Hidden Valley Hibiscus.

Also, my personal experience with a 10-year-old Hibiscus is that pinching out tips of stems in spring and summer increases flower production.

Growing avocado plant indoors

We have a large avocado plant (indoors) that is mystifying us. A couple months ago, it shed most of its leaves. The leaf would get droopy and the tips of the leaves would turn brown and dry out and then spread up the leaf. It got down to its last seven leaves and then seemed to stop, although all of these leaves have varying degrees of this leaf tip burn. Now over the last month or more, small new growth is appearing. They have not grown much at all and are only about an eighth of an inch long.

When growing an avocado (Persea species) indoors, you will need to be sure it is getting enough light. It is normal for the plant to drop older leaves. You should also keep the plant in a cool spot. According to The Houseplant Expert by D. G. Hessayon (Expert Books, 2001), your plant will do best if you repot it annually and pinch the tips to encourage bushy growth. Lee Reich discusses growing avocados indoors in an article (now archived) for California Rare Fruit Growers. Here is an excerpt:

“Indoors, avocado plants are often gangly and sparse with leaves. One reason for the plant’s gawky appearance indoors is light. Lack of sufficient light causes stems to stretch for it. Another reason is that avocados shed many buds along their stems, buds that might have grown into side branches. The result is a plant stretching out for light, sending out new growth mostly from the tips of the branches and shedding old leaves.

There are several things indoor gardeners can do to keep their plants more attractive. Most obvious is to give an avocado tree bright light. Also, the stretch for light is exaggerated when warmth stimulates growth, so the ideal spot for the plant is at the brightest window in the coolest room. Beyond that pruning back a stem or pinching out its growing tip stimulates branching by awaking dormant buds (not all are shed) further down the stem. There is nothing that can be done about the shedding of older leaves.”

Grown outdoors in an agricultural setting, avocado plants sometimes get leaf tip burn from salt accumulation, as this article from California Rare Fruit Growers explains. If you are using especially salty tap water or overfertilizing your plant, that might be causing the burnt leaf tips. Other causes could be lack of water, too frequent light watering, or poorly draining soil.