is happy to answer garden questions. Send them to her via firstname.lastname@example.org
"I have a pretty Nishiki willow which has been getting thinner each year, in spite of clipping it back in summer. I have taken out several dead branches and given it 20-20-20 fertilizer in water.
"Are fertilizer spikes any good for this type of tree? Also could snails on the tree be doing it harm?"
Pat Pryce, Maple Ridge
The Nishiki willow isn't always easy to grow well. It hates hot summers, dryness, and clay - especially compacted clay. In summer droughts it needs lots of water, but it should move freely through. It's happiest in well-drained situations. In poorly drained soil, some of the roots may rot; dead branches may be a clue that the tree has some root rot already.
It may enjoy a spot in the garden that has richer soil with less clay and is somewhat raised so drainage is better. Otherwise, just go on with what you're doing, but try mulching the tree with Sea Soil or weed-free compost.
The 20-20-20 fertilizer will do nicely, and several applications through summer should keep the tree nourished.
Clipping it back each summer should help, but if new shoots are sparse or dying back in winter, try removing one third of old wood in the dormant season.
All willows are very easy to grow from cuttings, though Nishiki willow cuttings will produce a bush, not a tree, since most Nishiki willows from garden centres have been grafted onto a trunk. The Nishiki willows I've seen grown from cuttings are low bushy shrubs, but still glorious.
So if your willow shows signs of dwindling away, regardless of what you do, you can propagate it from cuttings and enjoy it as a bush.
The Nishiki willow has a few other names, including Hakuro-Nishiki, dappled Japanese willow, variegated willow, or Fuji Nishiki.
"Where can I buy astrantia plants? Where do they like to be planted? How tall do they get- and so on?"
Ivy Rodgers, via email
he height of astrantia depends on the species. The tallest flower heads of astrantia major grow about 60 centimetres (two feet) high, while astrantia minor is the smallest, at 20-25 cm (eight or nine inches).
The foliage of both species is a low mound of leaves.
That can vary. Astrantia becomes taller or shorter, depending on how rich and moist the soil is. It prefers semi-shade, but tolerates full sun if there's moisture in the soil.
Most garden centres have some varieties of Astrantia major.
Flower colours vary from white and green, to white and pink, to deep reds and rosy pinks.
"I have a one-year-old wasabi plant in a big pot. It is outside, loves this cool weather, and is growing quickly.
"But where can I put it in hot weather?"
Vicki Williams, via email
Find the coolest, shadiest spot in your yard for your wasabi plant. It would be best if you put it on the north side of your house and blocked it from the lateafternoon sun.
It will need to be watered a great deal, probably twice a day in hot spells. The best wasabi is grown with its roots in cool, running water.